ELECTRONIC CIRCUIT AND DOHERTY AMPLIFIER CIRCUIT
20240429872 ยท 2024-12-26
Inventors
Cpc classification
H03F1/0288
ELECTRICITY
H03F2200/09
ELECTRICITY
International classification
H03F1/02
ELECTRICITY
Abstract
An electronic circuit includes: a variable amplitude control circuit that controls an amplitude of a first radio-frequency signal being a single-ended signal in accordance with a control signal that continuously changes and that outputs a second radio-frequency signal being a single-ended signal; and a balun that converts the second radio-frequency signal into differential signals and outputs a pair of third radio-frequency signals.
Claims
1. An electronic circuit comprising: a variable amplitude control circuit configured to control an amplitude of a first radio-frequency signal, which is a single-ended signal, in accordance with a control signal that continuously changes, and that is configured to output a second radio-frequency signal that is a single-ended signal; and a balun configured to convert the second radio-frequency signal into differential signals, and to output a pair of third radio-frequency signals.
2. The electronic circuit according to claim 1, further comprising: a detector circuit comprising a pair of first transistors constituting a differential pair, the first transistors having bases or gates to which the pair of third radio-frequency signals are input; wherein the detector circuit is configured to output a detected signal.
3. The electronic circuit according to claim 1, further comprising: a differential amplifier circuit configured to amplify the pair of third radio-frequency signals.
4. The electronic circuit according to claim 3, wherein the differential amplifier circuit comprises: a pair of second transistors constituting a differential pair, the second transistors having bases or gates to which the pair of third radio-frequency signals are input, wherein the pair of second transistors is configured to amplify the pair of third radio-frequency signals; and a third transistor having an emitter or source from which the third transistor a bias is supplied to the bases or gates of the pair of second transistors.
5. The electronic circuit according to claim 1, wherein the variable amplitude control circuit comprises: a fourth transistor having a base or gate to which the first radio-frequency signal is input, and an emitter or source electrically connected to an output node; and a fifth transistor having a collector or drain electrically connected to the emitter or source of the fourth transistor, and a base or gate to which the control signal is input.
6. The electronic circuit according to claim 1, wherein the variable amplitude control circuit comprises: a fourth transistor having a base or gate and a collector or drain electrically connected to each other, and an emitter or source that is electrically connected to an output node, the first radio-frequency signal being input to the emitter or source of the fourth transistor; and a fifth transistor having a collector or drain electrically connected to the emitter or source of the fourth transistor, and a base or gate to which the control signal is input.
7. The electronic circuit according to claim 5, wherein the variable amplitude control circuit further comprises: a first capacitor electrically connected between the base or gate and the collector or drain of the fifth transistor.
8. The electronic circuit according to claim 1, wherein the balun comprises: a pair of sixth transistors constituting a differential pair, and a second capacitor having a first end electrically connected to a base or gate of one of the pair of sixth transistors and a second end electrically connected to a reference potential, wherein the second radio-frequency signal is input to a base or gate of another one of the pair of sixth transistors, and wherein the pair of sixth transistors is configured to convert the second radio-frequency signal into the pair of third radio-frequency signals.
9. The electronic circuit according to claim 8, wherein the balun further comprises: a pair of seventh transistors configured to respectively amplify the pair of third radio-frequency signals.
10. The electronic circuit according to claim 9, wherein the balun comprises: an eighth transistor configured to supply a bias to the pair of sixth transistors, and a ninth transistor configured to supply a bias to each of the pair of seventh transistors.
11. The electronic circuit according to claim 1, wherein the balun comprises: a primary winding having a first end to which the second radio-frequency signal is input, and a second end connected to a reference potential or a low-impedance circuit, and a secondary winding having a first end and a second end from which the secondary winding is configured to output the pair of third radio-frequency signals.
12. A Doherty amplifier circuit comprising: a carrier amplifier configured to amplify a fifth radio-frequency signal split from a fourth radio-frequency signal; and a peaking amplifier configured to amplify a sixth radio-frequency signal split from the fourth radio-frequency signal, the sixth radio-frequency signal having a different phase than the fifth radio-frequency signal, wherein the carrier amplifier or the peaking amplifier is the electronic circuit according to claim 3.
13. The Doherty amplifier circuit according to claim 12, further comprising: a control circuit configured to output the control signal in accordance with a saturation signal representing saturation of the carrier amplifier or the peaking amplifier, and configured to output an envelope signal of the fourth radio-frequency signal, the fifth radio-frequency signal, or the sixth radio-frequency signal.
14. A Doherty amplifier circuit comprising: a carrier amplifier configured to amplify a fifth radio-frequency signal split from a fourth radio-frequency signal; a peaking amplifier configured to amplify a sixth radio-frequency signal split from the fourth radio-frequency signal, the sixth radio-frequency signal having a different phase than the fifth radio-frequency signal; a bias circuit configured to supply a bias to the peaking amplifier; and the electronic circuit according to claim 2 configured to: control, in accordance with a saturation signal representing saturation of the carrier amplifier or the peaking amplifier: an amplitude of at least one of the fourth radio-frequency signal, the fifth radio-frequency signal, or the sixth radio-frequency signal, or an amplitude of a signal obtained by attenuating at least one of the fourth radio-frequency signal, the fifth radio-frequency signal, or the sixth radio-frequency signal; convert into differential signals: the at least one of the fourth radio-frequency signal, the fifth radio-frequency signal, or the sixth radio-frequency signal, or the signal obtained by attenuating at least one of the fourth radio-frequency signal, the fifth radio-frequency signal, or the sixth radio-frequency signal into differential signals; detect the differential signals; and output the detected signal to the bias circuit.
15. The electronic circuit according to claim 6, wherein the variable amplitude control circuit further comprises: a first capacitor connected between the base or gate and the collector or drain of the fifth transistor.
16. A Doherty amplifier circuit comprising: a carrier amplifier configured to amplify a fifth radio-frequency signal split from a fourth radio-frequency signal; and a peaking amplifier configured to amplify a sixth radio-frequency signal split from the fourth radio-frequency signal, the sixth radio-frequency signal having a different phase than the fifth radio-frequency signal, wherein the carrier amplifier or the peaking amplifier is the electronic circuit according to claim 4.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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DETAILED DESCRIPTION
[0026] Embodiments of an electronic circuit and a Doherty amplifier circuit according to the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not to be limited by these embodiments. The embodiments are merely illustrative, and it goes without necessarily saying that configurations described in different embodiments can be partially replaced or combined. In second and subsequent embodiments, a description of things in common with a first embodiment is omitted, and only respects in which the second and subsequent embodiments differ from the first embodiment will be described. In particular, similar function effects achieved by similar configurations are not repeatedly described in each embodiment.
First Embodiment
[0027] Although a first embodiment will be described below, a comparative example will be described first to facilitate understanding of the first embodiment.
Comparative Example
[0028]
[0029] Radio-frequency signals RF-IN(P) and RF-IN(N), which are differential signals, are input to a differential variable amplitude control circuit 100. Furthermore, a signal BB-IN, which is a single-ended amplitude control signal, is input to the differential variable amplitude control circuit 100. The differential variable amplitude control circuit 100 controls amplitudes of the radio-frequency signals RF-IN(P) and RF-IN(N) in accordance with the signal BB-IN and outputs radio-frequency signals RF-OUT(P) and RF-OUT(N), which are differential signals.
[0030] Hereinafter, in some cases, the radio-frequency signals RF-IN(P) and RF-IN(N) are collectively referred to as a radio-frequency signal RF-IN, and the radio-frequency signals RF-OUT(P) and RF-OUT(N) are collectively referred to as a radio-frequency signal RF-OUT.
[0031]
[0032] A radio-frequency signal RF-OUT includes a differential mode signal component (differential component) represented by a waveform 110, and a common mode signal component (in-phase component) represented by a waveform 111.
[0033] The differential mode signal component represented by the waveform 110 has a frequency component of the radio-frequency signal RF-IN centered at a frequency f.sub.RF. The common mode signal component represented by the waveform 111 has a frequency component of the signal BB-IN centered at a frequency f.sub.BB. A maximum frequency of the frequency component of the signal BB-IN is a frequency f.sub.BB-MAX.
[0034] For example, if a differential detector circuit is connected to a stage subsequent to the differential variable amplitude control circuit 100, since the radio-frequency signal RF-OUT includes the common mode signal component, detection accuracy of the differential detector circuit decreases.
[0035] If the frequency f.sub.BB-MAX is less than 1% of the frequency f.sub.RF, the frequency component of the signal BB-IN can be removed by a capacitor for cutting off a bias. However, if the frequency f.sub.BB-MAX is not less than 1% of the frequency f.sub.RF due to an increase in the frequency of the radio-frequency signal RF-IN seen in recent years, a filter has to be provided separately to remove the frequency component of the signal BB-IN.
Overview of First Embodiment
[0036]
[0037] An electronic circuit 1 includes a variable amplitude control circuit 2 and a balun 3.
[0038] Although, as an example of the variable amplitude control circuit 2, a variable gain amplifier or a variable attenuator is given, the present disclosure is not limited to this.
[0039] A radio-frequency signal RF-IN, which is a single-ended signal, is input to the variable amplitude control circuit 2. Furthermore, a signal BB-IN, which is a single-ended amplitude control signal, is input to the variable amplitude control circuit 2. The variable amplitude control circuit 2 controls an amplitude of the radio-frequency signal RF-IN in accordance with the signal BB-IN and outputs a radio-frequency signal RF-MID, which is a single-ended signal, to the balun 3.
[0040] The balun 3 converts the radio-frequency signal RF-MID, which is a single-ended signal, into differential signals and outputs radio-frequency signals RF-OUT(P) and RF-OUT(N), which are the differential signals.
[0041]
[0042] A radio-frequency signal RF-OUT includes a differential mode signal component represented by a waveform 120, and a common mode signal component represented by a waveform 121.
[0043] The differential mode signal component represented by the waveform 120 has a frequency component of the radio-frequency signal RF-IN centered at a frequency f.sub.RF, and a frequency component of the signal BB-IN centered at a frequency f.sub.BB. The common mode signal component represented by the waveform 121 is constant at a low level over an entire frequency range.
[0044] The signal BB-IN can leak into an output terminal of the variable amplitude control circuit 2. That is, the frequency component of the signal BB-IN can be included in the radio-frequency signal RF-MID.
[0045] For example, if the balun 3 is a balun, such as an active balun, that has broadband characteristics, the balun 3 also converts a signal component of the signal BB-IN included in the radio-frequency signal RF-MID into differential signals. For this reason, the differential mode signal component represented by the waveform 120 has the frequency component centered at the frequency f.sub.BB.
[0046] Furthermore, for example, if the balun 3 is a balun that has narrowband characteristics centered at the frequency f.sub.RF, the balun 3 removes a signal component of the signal BB-IN included in the radio-frequency signal RF-MID and does not output the signal component.
[0047] Hence, even if the balun 3 is either of the above-described types, the radio-frequency signal RF-OUT is kept from including a signal component of the common mode signal BB-IN.
[0048] Thus, in the electronic circuit 1, for example, even if a differential detector circuit is connected to a stage subsequent to the balun 3, since the radio-frequency signal RF-OUT does not include any signal component of the common mode signal BB-IN, a decrease in detection accuracy of the differential detector circuit can be reduced.
[0049] In the electronic circuit 1, even if a frequency f.sub.BB-MAX is not less than 1% of the frequency f.sub.RF, an output error from the differential detector circuit in the subsequent stage can be reduced without necessarily using any filter separately.
[0050] Incidentally, for example, a case is examined where it is desired to obtain a signal obtained by adding information on the signal BB-IN to an envelope signal of the radio-frequency signal RF-IN. In general, as the simplest way to obtain a signal of interest, an envelope signal of the radio-frequency signal RF-IN is obtained by a detector circuit, and the envelope signal and the signal BB-IN are added by an adder.
[0051] However, when the frequencies of the envelope signal and the signal BB-IN increase, the adder is unable to follow the increases, and no signal of interest can be obtained.
[0052] Thus, in the electronic circuit 1 according to the first embodiment, the amplitude of the radio-frequency signal RF-IN is controlled in accordance with the signal BB-IN, and the radio-frequency signal whose amplitude has been controlled is converted into differential signals, thereby enabling detection by the circuit in the subsequent stage and making it possible to obtain a signal of interest.
[0053] Note the occurrence of a malfunction if a high frequency component is included in the signal BB-IN. As described later, the electronic circuit 1 according to the first embodiment can respond even if a high frequency component is included in the signal BB-IN.
Overall Configuration of First Embodiment
[0054]
[0055] The electronic circuit 1 includes the variable amplitude control circuit 2 and the balun 3. In the first embodiment, although the balun 3 is an active balun, the present disclosure is not limited to this.
[0056] Furthermore, in the first embodiment, although the electronic circuit 1 includes a detector circuit 4, the present disclosure is not limited to this. The detector circuit 4 detects a radio-frequency signal RF-OUT input from the balun 3 and outputs a detected signal S.sub.DET.
(Circuit Configuration of Variable Amplitude Control Circuit)
[0057] The variable amplitude control circuit 2 includes transistors Q.sub.AT1 and Q.sub.AT2, resistors R.sub.AT1, R.sub.AT2, and R.sub.AT3, and capacitors C.sub.AT1, C.sub.AT2, and C.sub.AT3.
[0058] The transistor Q.sub.AT1 corresponds to an example of fourth transistor in the present disclosure. The transistor Q.sub.AT2 corresponds to an example of fifth transistor in the present disclosure. The capacitor C.sub.AT3 corresponds to an example of first capacitor in the present disclosure.
[0059] In the present disclosure, although each transistor is a bipolar transistor, the present disclosure is not limited to this. Although, as an example of the bipolar transistor, a Heterojunction Bipolar Transistor (HBT) is given, the present disclosure is not limited to this. The transistor may be, for example, a Field Effect Transistor (FET). The transistor may be a multi-finger transistor including a plurality of unit transistors electrically connected in parallel. A unit transistor refers to a minimum component constituting the transistor.
[0060] If each transistor is an FET, the drain, gate, and source of the FET respectively correspond to the collector, base, and emitter of the bipolar transistor.
[0061] A collector of the transistor Q.sub.AT1 is electrically connected to a power supply potential Vcc and receives a supply of power. A base of the transistor Q.sub.AT1 is electrically connected to the power supply potential Vcc via the resistor R.sub.AT1 and is biased. An emitter of the transistor Q.sub.AT1 is electrically connected to a node N.sub.AT1.
[0062] The node N.sub.AT1 is an output node of the transistor Q.sub.AT1.
[0063] The base of the transistor Q.sub.AT1 is electrically connected to an input terminal 2a via the capacitor C.sub.AT1, which is a DC cut capacitor. A radio-frequency signal RF-IN, which is a single-ended signal, is input to the input terminal 2a. Thus, the radio-frequency signal RF-IN is input to the base of the transistor Q.sub.AT1, the transistor Q.sub.AT1 amplifies the radio-frequency signal RF-IN and outputs a radio-frequency signal RF-MID from the emitter to the node N.sub.AT1.
[0064] The radio-frequency signal RF-IN corresponds to an example of first radio-frequency signal in the present disclosure.
[0065] An emitter of the transistor Q.sub.AT2 is electrically connected to a reference potential. That is, the transistor Q.sub.AT2 is emitter-grounded. Although, as an example of the reference potential, a ground potential is given, the present disclosure is not limited to this. A collector of the transistor Q.sub.AT2 is electrically connected to the node N.sub.AT1 via the resistor R.sub.AT2. A base of the transistor Q.sub.AT2 is electrically connected to an input terminal 2b via the resistor R.sub.AT3. A signal BB-IN, which is a single-ended amplitude control signal, is input to the input terminal 2b. Thus, the signal BB-IN is input to the base of the transistor Q.sub.AT2.
[0066] The signal BB-IN corresponds to an example of control signal in the present disclosure.
[0067] In the present disclosure, the signal BB-IN is a signal that continuously changes and is continuously supplied. That is, the signal BB-IN is input to the transistor Q.sub.AT2 at all times and can continuously take on values from a first value that controls the transistor Q.sub.AT2 so as to put the transistor Q.sub.AT2 into a non-conducting (cutoff) state to a second value that controls the transistor Q.sub.AT2 so as to put the transistor Q.sub.AT2 into a conducting (saturation) state.
[0068] One end of the capacitor C.sub.AT3 is electrically connected to the base of the transistor Q.sub.AT2. The other end of the capacitor C.sub.AT3 is electrically connected to the collector of the transistor Q.sub.AT2. Thus, negative feedback is applied to the transistor Q.sub.AT2 at a frequency of the radio-frequency signal RF-IN.
[0069] One end of the capacitor C.sub.AT2, which is a DC cut capacitor, is electrically connected to the node N.sub.AT1. From the other end of the capacitor C.sub.AT2, a single-ended radio-frequency signal RF-MID obtained by controlling the amplitude of the radio-frequency signal RF-IN in accordance with the signal BB-IN is output to the balun 3.
[0070] The radio-frequency signal RF-MID corresponds to an example of second radio-frequency signal in the present disclosure.
(Operation of Variable Amplitude Control Circuit)
[0071] The transistor Q.sub.AT1 is connected to the resistor R.sub.AT2 and the transistor Q.sub.AT2 so as to establish an emitter-follower connection. In the variable amplitude control circuit 2, the transistor Q.sub.AT1 operates as an emitter follower to thereby perform current amplification.
[0072] The transistor Q.sub.AT2 is controlled in response to a signal value of the signal BB-IN so as to be brought into conduction or non-conduction. In the present disclosure, note that, since the signal BB-IN is a signal that continuously changes and is continuously supplied, the transistor Q.sub.AT2 is continuously controlled between conduction and non-conduction.
[0073] For example, when the transistor Q.sub.AT2 enters a conducting state, an emitter bias current flows to the transistor Q.sub.AT1, and thus transistor Q.sub.AT1 performs current amplification. On the other hand, when the transistor Q.sub.AT2 enters a non-conducting state, no emitter bias current flows to the transistor Q.sub.AT1, and thus the transistor Q.sub.AT1 does not perform current amplification. That is, the variable amplitude control circuit 2 is a circuit that can control the amplitude of the radio-frequency signal RF-IN in response to the signal BB-IN.
[0074] Hence, the variable amplitude control circuit 2 has characteristics in which the variable amplitude control circuit 2 increases the radio-frequency signal RF-MID when the signal BB-IN increases and in which the variable amplitude control circuit 2 reduces the radio-frequency signal RF-MID when the signal BB-IN decreases.
[0075] Thus, in the variable amplitude control circuit 2, the signal BB-IN is a signal that continuously changes and is supplied, therefor facilitating a reduction in deterioration of the quality of an output signal from the variable amplitude control circuit 2. For example, if the signal BB-IN is a signal that discretely changes and is supplied (for example, if a variable amplitude control circuit is switched between an operating state and a non-operating state with a switch or the like for use), a waveform of an output signal from the variable amplitude control circuit discontinuously changes. At this time, there is a possibility that an unwanted signal may be caused by a discontinuous change in an output signal waveform and the quality of an output signal from the variable amplitude control circuit may decrease. On the other hand, in the variable amplitude control circuit 2 according to this embodiment, since the signal BB-IN is a signal that continuously changes and is supplied, a waveform of an output signal from the variable amplitude control circuit 2 also continuously changes, and unwanted noise is less likely to be caused.
[0076] The variable amplitude control circuit 2 can control the amplitude of the radio-frequency signal RF-IN fast by using the transistor Q.sub.AT1 connected so as to establish an emitter-follower connection.
[0077] Furthermore, the variable amplitude control circuit 2 includes the capacitor C.sub.AT3, thereby making it possible to reduce the occurrence of a malfunction.
[0078] For example, a radio-frequency signal RF-IN that has leaked can be input to the input terminal 2b to which the signal BB-IN is input.
[0079] If there is no capacitor C.sub.AT3, since the transistor Q.sub.AT2 is emitter-grounded, the transistor Q.sub.AT2 amplifies the radio-frequency signal RF-IN that has leaked. Subsequently, the radio-frequency signal amplified by the transistor Q.sub.AT2 and the radio-frequency signal RF-MID amplified by the transistor Q.sub.AT1 mix at the node N.sub.AT1 and interfere with each other, and the variable amplitude control circuit 2 can malfunction.
[0080] Thus, the variable amplitude control circuit 2 includes the capacitor C.sub.AT3 electrically connected between the base and collector of the transistor Q.sub.AT2. In the variable amplitude control circuit 2, the capacitor C.sub.AT3 Can reduce the gain of the transistor Q.sub.AT2 with its emitter grounded at the frequency of the radio-frequency signal RF-IN. Consequently, the variable amplitude control circuit 2 can reduce the above-described interference and reduce the occurrence of a malfunction.
(Circuit Configuration of Balun)
[0081] The balun 3 includes transistors Q.sub.AB1 to Q.sub.AB8, resistors R.sub.AB1 to R.sub.AB6, and capacitors C.sub.AB1 to C.sub.AB4.
[0082] The transistors Q.sub.AB1 and Q.sub.AB2 correspond to an example of a pair of sixth transistors in the present disclosure. The transistors Q.sub.AB3 and Q.sub.AB4 correspond to an example of a pair of seventh transistors in the present disclosure. The transistor Q.sub.AB8 corresponds to an example of eighth transistor in the present disclosure. The transistors Q.sub.AB5 and Q.sub.AB6 correspond to an example of ninth transistor in the present disclosure. The capacitor C.sub.AB3 corresponds to an example of second capacitor in the present disclosure. In this embodiment, note that, although ninth transistor refers to a pair of transistors Q.sub.AB5 and Q.sub.AB6, the number of ninth transistors is not limited to this. For example, either the transistor Q.sub.AB5 or Q.sub.AB6 may be omitted.
[0083] The transistors Q.sub.AB1 and Q.sub.AB2 are transistors constituting a differential pair. The transistors Q.sub.AB3 and Q.sub.AB4 are output transistors. The transistors Q.sub.AB5 to Q.sub.AB8 are transistors that supply a bias to the transistors Q.sub.AB1 to Q.sub.AB4.
[0084] One end of the resistor R.sub.AB1 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.AB1 is electrically connected to a node N.sub.AB1. A collector of the transistor Q.sub.AB1 is electrically connected to the node N.sub.AB1. The collector of the transistor Q.sub.AB1 is electrically connected to the power supply potential Vcc via the resistor R.sub.AB1 and receives a supply of power.
[0085] The node N.sub.AB1 is an output node of the transistor Q.sub.AB1.
[0086] One end of the resistor R.sub.AB3 is electrically connected to the node N.sub.AB1. The other end of the resistor R.sub.AB3 is electrically connected to a base of the transistor Q.sub.AB1. The base of the transistor Q.sub.AB1 is electrically connected to the power supply potential Vcc via the resistors R.sub.AB1 and R.sub.AB3 and is biased. The radio-frequency signal RF-MID is input from the variable amplitude control circuit 2 to the base of the transistor Q.sub.AB1.
[0087] One end of the resistor R.sub.AB2 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.AB2 is electrically connected to a node N.sub.AB2. A collector of the transistor Q.sub.AB2 is electrically connected to the node N.sub.AB2. The collector of the transistor Q.sub.AB2 is electrically connected to the power supply potential Vcc via the resistor R.sub.AB2 and receives a supply of power.
[0088] The node N.sub.AB2 is an output node of the transistor Q.sub.AB2.
[0089] One end of the resistor RABA is electrically connected to the node N.sub.AB2. The other end of the resistor RABA is electrically connected to a base of the transistor Q.sub.AB2. The base of the transistor Q.sub.AB2 is electrically connected to the power supply potential Vcc via the resistors R.sub.AB2 and R.sub.AB4 and is biased. One end of the capacitor C.sub.AB3 is electrically connected to the base of the transistor Q.sub.AB2. The other end of the capacitor C.sub.AB3 is electrically connected to the reference potential.
[0090] One end of the resistor R.sub.AB6 is electrically connected to a node N.sub.AB3. The other end of the resistor R.sub.AB6 is electrically connected to a collector and a base of the transistor Q.sub.AB7. An emitter of the transistor Q.sub.AB7 is electrically connected to the reference potential. That is, the transistor Q.sub.AB7 is diode-connected.
[0091] A bias current BIAS.sub.AB is supplied to the node N.sub.AB3. The resistor R.sub.AB6 and the transistor Q.sub.AB7 generate a fixed potential at the node N.sub.AB3.
[0092] One end of the capacitor C.sub.AB4 is electrically connected to the node N.sub.AB3. The other end of the capacitor C.sub.AB4 is electrically connected to the reference potential. The capacitor C.sub.AB4 stabilizes a potential of the node N.sub.AB3. An emitter of the transistor Q.sub.AB8 is electrically connected to the reference potential. A base of the transistor Q.sub.AB8 is electrically connected to the collector and base of the transistor Q.sub.AB7. That is, the transistor Q.sub.AB8 is connected to the transistor Q.sub.AB2 so as to establish a current-mirror connection. A collector of the transistor Q.sub.AB8 is electrically connected to an emitter of the transistor Q.sub.AB1 and an emitter of the transistor Q.sub.AB2. The transistor Q.sub.AB8 supplies a bias to the emitter of the transistor Q.sub.AB1 and the emitter of the transistor Q.sub.AB2.
[0093] Thus, the transistor Q.sub.AB1 is emitter-grounded. On the other hand, the transistor Q.sub.AB2 is base-grounded by the capacitor C.sub.AB3.
[0094] A collector of the transistor Q.sub.AB3 is electrically connected to the power supply potential Vcc and receives a supply of power. A base of the transistor Q.sub.AB3 is electrically connected to the node N.sub.AB1. An emitter of the transistor Q.sub.AB3 is electrically connected to a node N.sub.AB4.
[0095] A collector of the transistor Q.sub.AB5 is electrically connected to the node N.sub.AB4. An emitter of the transistor Q.sub.AB5 is electrically connected to the reference potential. One end of the resistor R.sub.AB5 is electrically connected to the node N.sub.AB3. The other end of the resistor R.sub.AB5 is electrically connected to a base of the transistor Q.sub.AB5. That is, the transistor Q.sub.AB5 is connected to the transistor Q.sub.AB2 so as to establish a current-mirror connection. The transistor Q.sub.AB5 supplies a bias to the emitter of the transistor Q.sub.AB3.
[0096] A collector of the transistor Q.sub.AB4 is electrically connected to the power supply potential Vcc and receives a supply of power. A base of the transistor Q.sub.AB4 is electrically connected to the node N.sub.AB2. An emitter of the transistor Q.sub.AB4 is electrically connected to a node N.sub.AB5.
[0097] A collector of the transistor Q.sub.AB6 is electrically connected to the node N.sub.AB5. An emitter of the transistor Q.sub.AB6 is electrically connected to the reference potential. The other end of the resistor R.sub.AB5 is electrically connected to a base of the transistor Q.sub.AB6. That is, the transistor Q.sub.AB6 is connected to the transistor Q.sub.AB7 so as to establish a current-mirror connection. The transistor Q.sub.AB6 supplies a bias to the emitter of the transistor Q.sub.AB4.
[0098] One end of the capacitor C.sub.AB2, which is a DC cut capacitor, is electrically connected to the node N.sub.AB5. From the other end of the capacitor C.sub.AB2, a radio-frequency signal RF-OUT(P) is output to the detector circuit 4.
[0099] One end of the capacitor C.sub.AB1, which is a DC cut capacitor, is electrically connected to the node N.sub.AB1. From the other end of the capacitor C.sub.AB4, a radio-frequency signal RF-OUT(N) is output to the detector circuit 4.
[0100] The radio-frequency signals RF-OUT(P) and RF-OUT(N) correspond to an example of a pair of third radio-frequency signals in the present disclosure.
(Operation of Balun)
[0101] The transistor Q.sub.AB1 operates with its emitter grounded. The transistor Q.sub.AB2 operates with its base grounded, and an emitter current of the transistor Q.sub.AB1 is input to the emitter of the transistor Q.sub.AB2. Thus, signals having opposite phases are obtained from the collector of the transistor Q.sub.AB1 (node N.sub.AB1) and the collector of the transistor Q.sub.AB2 (node N.sub.AB2). That is, a differential pair of transistors Q.sub.AB1 and Q.sub.AB2 provide a voltage gain, convert the radio-frequency signal RF-MID into differential signals, and output the radio-frequency signals RF-OUT(P) and RF-OUT(N).
[0102] The balun 3 has characteristics in which the balun 3 increases the radio-frequency signals RF-OUT(P) and RF-OUT(N) when the radio-frequency signal RF-MID increases and in which the balun 3 reduces the radio-frequency signals RF-OUT(P) and RF-OUT(N) when the radio-frequency signal RF-MID decreases.
[0103] If an input impedance of a circuit in the stage subsequent to the balun 3 is high, output signals from the collector of the transistor Q.sub.AB1 (node N.sub.AB1) and the collector of the transistor Q.sub.AB2 (node N.sub.AB2) may be regarded as output signals of the balun 3.
[0104] In this case, note that there is a possibility that the output signals from the collector of the transistor Q.sub.AB1 and the collector of the transistor Q.sub.AB2 may be reduced, for example, by stray capacitances generated at the nodes N.sub.AB1 and N.sub.AB2.
[0105] Thus, the balun 3 includes the transistors Q.sub.AB3 and Q.sub.AB4, which are output transistors. Each of the transistors Q.sub.AB3 and Q.sub.AB4 operates as an emitter follower. For this reason, the balun 3 can output the radio-frequency signals RF-OUT(P) and RF-OUT(N) obtained by the transistors Q.sub.AB3 and Q.sub.AB4 amplifying the respective output signals from the collector of the transistor Q.sub.AB1 and the collector of the transistor Q.sub.AB2. In other words, the transistors Q.sub.AB3 and Q.sub.AB4 can reduce impedances of loads on the collector of the transistor Q.sub.AB1 and the collector of the transistor Q.sub.AB2.
[0106] Bias points of the transistors Q.sub.AB3 and Q.sub.AB4 are determined by the transistors Q.sub.AB5 and Q.sub.AB6 that are connected to the transistor Q.sub.AB2 so as to establish a current-mirror connection.
[0107] The balun 3 is an active balun that can convert an in-phase signal into differential signals over a wide frequency band including a low-frequency region if the electrostatic capacity of the capacitor C.sub.AB3 for implementing amplification by the transistor Q.sub.AB2 with its base grounded is increased. That is, the balun 3 can also convert the input signal BB-IN into differential signals and output the differential signals. Thus, no common mode signal BB-IN appears in the radio-frequency signals RF-OUT(P) and RF-OUT(N).
(Configuration of Detector Circuit)
[0108] The detector circuit 4 includes transistors Q.sub.DE1 to Q.sub.DE7, resistors R.sub.DE1 to R.sub.DE3, and a capacitor C.sub.DE1.
[0109] The transistors Q.sub.DE1 and Q.sub.DE2 are transistors constituting a differential pair.
[0110] The transistors Q.sub.DE1 and Q.sub.DE2 correspond to an example of a pair of first transistors in the present disclosure.
[0111] The transistors Q.sub.DE3 to Q.sub.DE7 and the resistors R.sub.DE1 to R.sub.DE3 supply a bias to bases and emitters of the transistors Q.sub.DE1 and Q.sub.DE2.
[0112] Collectors of the transistors Q.sub.DE1 and Q.sub.DE2 are electrically connected to the power supply potential Vcc and receive a supply of power. The emitters of the transistors Q.sub.DE1 and Q.sub.DE2 are electrically connected to a node N.sub.DE1.
[0113] The node N.sub.DE1 is an output node of the transistors Q.sub.DE1 and Q.sub.DE2.
[0114] One end of the resistor R.sub.DE3, one end of the resistor R.sub.DE1, and one end of the resistor R.sub.DE2 are electrically connected to a node N.sub.DE2.
[0115] The other end of the resistor R.sub.DE3 is electrically connected to a collector and a base of the transistor Q.sub.DE6. That is, the transistor Q.sub.DE6 is diode-connected. An emitter of the transistor Q.sub.DE6 is electrically connected to a collector and a base of the transistor Q.sub.DE7. That is, the transistor Q.sub.DE7 is diode-connected. An emitter of the transistor Q.sub.DE7 is electrically connected to the reference potential.
[0116] A bias current BIAS.sub.DE is input to the node N.sub.DE2. The resistor R.sub.DE3, the transistor Q.sub.DE6, and the transistor Q.sub.DE7 generate a fixed voltage. This voltage is input to the base of the transistor Q.sub.DE1 via the resistor R.sub.DE1 and is also input to the base of the transistor Q.sub.DE2 via the resistor R.sub.DE2.
[0117] Each of the transistors Q.sub.DE3, Q.sub.DE4, and Q.sub.DE5 is connected to the transistor Q.sub.DE7 so as to establish a current-mirror connection.
[0118] A collector of the transistor Q.sub.DE4 is electrically connected to the base of the transistor Q.sub.DE1. Thus, the transistor Q.sub.DE4 can adjust a base current of the transistor Q.sub.DE1.
[0119] A collector of the transistor Q.sub.DE5 is electrically connected to the base of the transistor Q.sub.DE2. Thus, the transistor Q.sub.DE5 can adjust a base current of the transistor Q.sub.DE2.
[0120] A collector of the transistor Q.sub.DE3 is electrically connected to the node N.sub.DE1. Thus, the transistor Q.sub.DE3 Can adjust emitter currents of the transistors Q.sub.DE1 and Q.sub.DE2.
[0121] The radio-frequency signals RF-OUT(P) and RF-OUT(N) are respectively input to the base of the transistor Q.sub.DE2 and the base of the transistor Q.sub.DE1.
[0122] One end of the capacitor C.sub.DE1 is electrically connected to the node N.sub.DE1. The other end of the capacitor C.sub.DE1 is electrically connected to the reference potential.
[0123] The capacitor C.sub.DE1 is charged or discharged by a difference between the emitter currents of the transistors Q.sub.DE1 and Q.sub.DE2 and a collector current of the transistor Q.sub.DE3. A voltage of the capacitor C.sub.DE1 is a detected signal S.sub.DET obtained through detection of the radio-frequency signals RF-OUT(P) and RF-OUT(N). The capacitor C.sub.DE1 terminates a high frequency component (for example, a carrier frequency signal component) of the detected signal S.sub.DET at the reference potential to remove the component and passes only a low frequency component.
(Operation of Detector Circuit)
[0124] When the radio-frequency signal RF-OUT(P) is not less than a threshold voltage of the transistor Q.sub.DE2, the transistor Q.sub.DE2 enters an ON state and outputs an emitter current. When the radio-frequency signal RF-OUT(N) is not less than a threshold voltage of the transistor Q.sub.DE1, the transistor Q.sub.DE1 enters an ON state and outputs an emitter current.
[0125] That is, as amplitudes of the radio-frequency signals RF-OUT(P) and RF-OUT(N) increase (as the power of the radio-frequency signal RF-OUT increases), the emitter currents of the transistors Q.sub.DE1 and Q.sub.DE2 increase. Furthermore, as the amplitudes of the radio-frequency signals RF-OUT(P) and RF-OUT(N) decrease (as the power of the radio-frequency signal RF-OUT decreases), the emitter currents of the transistors Q.sub.DE1 and Q.sub.DE2 decrease.
[0126] The voltage of the capacitor C.sub.DE1 increases as the power of the radio-frequency signal RF-OUT increases. Furthermore, the voltage of the capacitor C.sub.DE1 decreases as the power of the radio-frequency signal RF-OUT decreases.
[0127] That is, the detector circuit 4 has characteristics in which the detector circuit 4 increases the detected signal S.sub.DET when the radio-frequency signal RF-OUT increases and in which the detector circuit 4 reduces the detected signal S.sub.DET when the radio-frequency signal RF-OUT decreases.
[0128] Thus, the detector circuit 4 can detect the radio-frequency signals RF-OUT(P) and RF-OUT(N) and output the detected signal S.sub.DET.
SUMMARY
[0129] (1) The variable amplitude control circuit 2 controls the amplitude of the radio-frequency signal RF-IN, which is a single-ended signal, in accordance with the signal BB-IN and outputs the radio-frequency signal RF-MID, which is a single-ended signal, to the balun 3. The balun 3 converts the radio-frequency signal RF-MID, which is a single-ended signal, into the radio-frequency signals RF-OUT(P) and RF-OUT(N), which are differential signals.
[0130] Note that the radio-frequency signal RF-MID can include a signal component of the signal BB-IN.
[0131] However, for example, if the balun 3 is a balun that has broadband characteristics, the balun 3 also converts a signal component of the signal BB-IN included in the radio-frequency signal RF-MID into differential signals.
[0132] Furthermore, for example, if the balun 3 is a balun that has narrowband characteristics, the balun 3 removes a signal component of the signal BB-IN included in the radio-frequency signal RF-MID and does not output the signal component.
[0133] Hence, even if the balun 3 is either of the above-described types, the electronic circuit 1 can keep the radio-frequency signals RF-OUT(P) and RF-OUT(N) from including a signal component of the common mode signal BB-IN.
[0134] Thus, in the electronic circuit 1, even if the detector circuit 4 is connected to the stage subsequent to the balun 3, since the radio-frequency signals RF-OUT(P) and RF-OUT(N) do not include any common mode signal component, a decrease in detection accuracy of the detector circuit 4 can be reduced.
[0135] (2) In comparison with a single-ended detector circuit, in the differential detector circuit 4, the number of times detection is performed doubles, and the electrostatic capacity of the capacitor C.sub.DE1 can be reduced to half, therefore enabling the detector circuit 4 to operate four times faster. Hence, the differential detector circuit 4 is indispensable to an application that expects fast operation.
[0136] However, in the detector circuit 4, an input terminal is connected to an output terminal in a direct-current (DC) manner (or via a stage of a capacitor for cutting off a bias). For that reason, the detector circuit 4 has characteristics in which, when a common mode signal is input, a malfunction in which the common mode signal leaks directly into the output terminal occurs.
[0137] Hence, as in a technique disclosed in Patent Document 1, when a circuit in which a control signal leaks into an output terminal as a common mode component is used in a stage preceding the detector circuit 4, a malfunction is caused.
[0138] On the other hand, in the electronic circuit 1, the variable amplitude control circuit 2 outputs, to the balun 3, the radio-frequency signal RF-MID obtained by controlling the amplitude of the single-ended radio-frequency signal RF-IN.
[0139]
[0140] The radio-frequency signal RF-MID includes a common mode signal component represented by a waveform 130. The common mode signal component represented by the waveform 130 has a frequency component 131 of a radio-frequency signal centered at the frequency f.sub.RF, and a frequency component 132 of the signal BB-IN of not more than the frequency f.sub.BB-MAX.
[0141] The balun 3 is an active balun and converts a single-ended signal with up to a low frequency into differential signals.
[0142]
[0143] The radio-frequency signal RF-OUT includes a differential mode signal component represented by a waveform 140, and a common mode signal component represented by a waveform 141. The differential mode signal component represented by the waveform 140 has a frequency component 142 of a radio-frequency signal centered at the frequency f.sub.RF, and a frequency component 143 of the signal BB-IN of not more than the frequency f.sub.BB-MAX. The common mode signal component represented by the waveform 141 is constant at a low level over an entire frequency range.
[0144] Thus, the electronic circuit 1 can keep a common mode signal from being input to the detector circuit 4, therefore enabling the detector circuit 4 to operate fast.
[0145] (3) Furthermore, the variable amplitude control circuit 2 includes the transistor Q.sub.AT1 having the collector electrically connected to the power supply potential Vcc, the base to which the radio-frequency signal RF-IN is input, and the emitter electrically connected to the node N.sub.AT1. Additionally, the variable amplitude control circuit 2 includes the transistor Q.sub.AT2 having the collector electrically connected to the node N.sub.AT1, the base to which the signal BB-IN is input, and the emitter electrically connected to the reference potential.
[0146] Note that the radio-frequency signal RF-IN can be input to the base of the transistor Q.sub.AT2.
[0147] However, the variable amplitude control circuit 2 includes the capacitor C.sub.AT3 having one end electrically connected to the base of the transistor Q.sub.AT2 and the other end electrically connected to the collector of the transistor Q.sub.AT2.
[0148] In the variable amplitude control circuit 2, the capacitor C.sub.AT3 can reduce the gain of the transistor Q.sub.AT2 with its emitter grounded at the frequency of the radio-frequency signal RF-IN.
[0149] Consequently, the variable amplitude control circuit 2 can keep a radio-frequency signal amplified by the transistor Q.sub.AT2 and a radio-frequency signal amplified by the transistor Q.sub.AT1 from mixing at the node NAM and interfering with each other. Hence, the electronic circuit 1 can reduce the occurrence of a malfunction.
[0150] (4) In the electronic circuit 1, even if the frequency f.sub.BB-MAX is not less than 1% of the frequency f.sub.RF, an output error from the detector circuit 4 can be reduced without necessarily using any filter separately.
[0151] (5) In the electronic circuit 1, in a frequency region not less than 1% of the frequency f.sub.RF, even if the spectral density of the signal BB-IN is not less than 10% of the entire spectrum of the signal BB-IN, an output error from the detector circuit 4 can be reduced.
[0152] The electronic circuit 1 is more effective when the frequency of the radio-frequency signal RF-IN and the frequency of the signal BB-IN is closer to each other.
Second Embodiment
[0153] The electronic circuit 1 according to the first embodiment has characteristics in which the electronic circuit 1 increases the detected signal S.sub.DET when the radio-frequency signal RF-IN increases and in which the electronic circuit 1 reduces the detected signal S.sub.DET when the radio-frequency signal RF-IN decreases.
[0154] On the other hand, an electronic circuit 1A according to a second embodiment has characteristics in which the electronic circuit 1A reduces the detected signal S.sub.DET When the radio-frequency signal RF-IN increases and in which the electronic circuit 1A increases the detected signal S.sub.DET When the radio-frequency signal RF-IN decreases.
(Overall Configuration)
[0155] Of components in the second embodiment, components that are the same as components in the first embodiment are denoted by the same reference signs, and a description thereof is omitted.
[0156]
[0157] In comparison with the electronic circuit 1 according to the first embodiment (see
(Configuration of Detector Circuit)
[0158] The detector circuit 4A includes transistors Q.sub.DE1 to Q.sub.DE6, resistors R.sub.DE1 to R.sub.DE4, and the capacitor C.sub.DE1.
[0159] The transistors Q.sub.DE1 and Q.sub.DE2 are transistors constituting a differential pair.
[0160] The transistors Q.sub.DE1 and Q.sub.DE2 correspond to an example of a pair of first transistors in the present disclosure.
[0161] The resistor R.sub.DE1 supplies a bias to the collectors of the transistors Q.sub.DE1 and Q.sub.DE2.
[0162] The transistors Q.sub.DE3 to Q.sub.DE6 and the resistors R.sub.DE2 to R.sub.DE4 supply a bias to the bases of the transistors Q.sub.DE1 and Q.sub.DE2.
[0163] One end of the resistor R.sub.DE1 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.DE1 is electrically connected to the node N.sub.DE1.
[0164] The collectors of the transistors Q.sub.DE1 and Q.sub.DE2 are electrically connected to the node N.sub.DE1 and receive a supply of power via the resistor R.sub.DE1. The emitters of the transistors Q.sub.DE1 and Q.sub.DE2 are electrically connected to the reference potential.
[0165] The node N.sub.DE1 is an output node of the transistors Q.sub.DE1 and Q.sub.DE2.
[0166] A bias current BIAS.sub.DE is supplied to one end of the resistor R.sub.DE4. The other end of the resistor R.sub.DE4 is electrically connected to the node N.sub.DE2.
[0167] The collector and base of the transistor Q.sub.DE5 are electrically connected to the node N.sub.DE2. That is, the transistor Q.sub.DE5 is diode-connected. An emitter of the transistor Q.sub.DE5 is electrically connected to the collector and base of the transistor Q.sub.DE6. That is, the transistor Q.sub.DE6 is diode-connected. The emitter of the transistor Q.sub.DE6 is electrically connected to the reference potential.
[0168] The transistors Q.sub.DE5 and Q.sub.DE6 generate a fixed voltage at the node N.sub.DE2. This voltage is input to a base of the transistor Q.sub.DE3 and a base of the transistor Q.sub.DE4.
[0169] The collectors of the transistors Q.sub.DE3 and Q.sub.DE4 are electrically connected to the power supply potential Vcc and receive a supply of power.
[0170] An emitter of the transistor Q.sub.DE3 is electrically connected to one end of the resistor R.sub.DE2. The other end of the resistor R.sub.DE2 is electrically connected to the base of the transistor Q.sub.DE1. Thus, the transistor Q.sub.DE3 can adjust a base current of the transistor Q.sub.DE1.
[0171] An emitter of the transistor Q.sub.DE4 is electrically connected to one end of the resistor R.sub.DE3. The other end of the resistor R.sub.DE3 is electrically connected to the base of the transistor Q.sub.DE2. Thus, the transistor Q.sub.DE4 can adjust a base current of the transistor Q.sub.DE2.
[0172] The radio-frequency signals RF-OUT(P) and RF-OUT(N) are respectively input to the base of the transistor Q.sub.DE2 and the base of the transistor Q.sub.DE1.
[0173] One end of the capacitor C.sub.DE1 is electrically connected to the node N.sub.DE1. The other end of the capacitor C.sub.DE1 is electrically connected to the reference potential.
(Operation of Detector Circuit)
[0174] Collector currents of the transistors Q.sub.DE1 and Q.sub.DE2 increase when the radio-frequency signal RF-OUT increases, a voltage drop across the resistor R.sub.DE1 increases, and thus a potential of the node N.sub.DE1 decreases. Collector currents of the transistors Q.sub.DE1 and Q.sub.DE2 decrease when the radio-frequency signal RF-OUT decreases, a voltage drop across the resistor R.sub.DE1 decreases, and thus a potential of the node N.sub.DE1 increases.
[0175] That is, the detector circuit 4A has characteristics in which the detected signal S.sub.DET decreases when the radio-frequency signal RF-OUT increases and in which the detected signal S.sub.DET increases when the radio-frequency signal RF-OUT decreases.
[0176] The variable amplitude control circuit 2 and the balun 3 in preceding stages have characteristics in which the variable amplitude control circuit 2 and the balun 3 increase the radio-frequency signal RF-OUT when the radio-frequency signal RF-IN increases and in which the variable amplitude control circuit 2 and the balun 3 reduce the radio-frequency signal RF-OUT when the radio-frequency signal RF-IN decreases.
[0177] Hence, the electronic circuit 1A has characteristics in which the electronic circuit 1A reduces the detected signal S.sub.DET when the radio-frequency signal RF-IN increases and in which the electronic circuit 1A increases the detected signal S.sub.DET when the radio-frequency signal RF-IN decreases.
[0178] The detector circuit 4 (see
[0179] When a common mode signal is input to the detector circuit 4A, the detector circuit 4A outputs the common mode signal directly as in the detector circuit 4. Hence, it is desirable that the balun 3 be provided in a stage preceding the detector circuit 4A.
Third Embodiment
[0180] The electronic circuit 1 according to the first embodiment and the electronic circuit 1A according to the second embodiment have characteristics in which the electronic circuit 1 and the electronic circuit 1A increase the radio-frequency signal RF-OUT when the signal BB-IN increases and in which the electronic circuit 1 and the electronic circuit 1A reduce the radio-frequency signal RF-OUT when the signal BB-IN decreases.
[0181] In some cases, however, characteristics are asked for in which the radio-frequency signal RF-OUT is reduced when the signal BB-IN increases and the radio-frequency signal RF-OUT is increased when the signal BB-IN decreases.
[0182] An electronic circuit 1B according to a third embodiment has such characteristics.
(Overall Configuration)
[0183] Of components in the third embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0184]
[0185] In comparison with the electronic circuit 1 according to the first embodiment (see
(Configuration of Variable Amplitude Control Circuit)
[0186] In comparison with the variable amplitude control circuit 2 (see
[0187] The transistor Q.sub.AT1 corresponds to an example of fourth transistor in the present disclosure. The transistor Q.sub.AT2 corresponds to an example of fifth transistor in the present disclosure.
(Operation of Variable Amplitude Control Circuit)
[0188] When the signal BB-IN increases, the transistor Q.sub.AT2 enters a conducting state as in the variable amplitude control circuit 2, and a potential of the node N.sub.AT1 decreases. Thus, the transistor Q.sub.AT1 also enters a conducting state. The transistor Q.sub.AT1 is an emitter-follower amplifier circuit, and thus, when the transistor Q.sub.AT1 enters a conducting state, the transistor Q.sub.AT1 amplifies an input current signal and outputs the signal as a radio-frequency signal RF-MID.
[0189] When the signal BB-IN decreases, a current flowing to the collector of the transistor Q.sub.AT2 decreases. Thus, the transistor Q.sub.AT1 also enters a non-conducting state. As a result, the transistor Q.sub.AT1 does not perform emitter-follower amplification, and the signal of the radio-frequency signal RF-MID decreases.
[0190] Hence, the variable amplitude control circuit 2B has characteristics in which the variable amplitude control circuit 2B increases the radio-frequency signal RF-MID when the signal BB-IN increases and in which the variable amplitude control circuit 2B reduces the radio-frequency signal RF-MID when the signal BB-IN decreases.
[0191] The balun 3 has characteristics in which the balun 3 increases the radio-frequency signal RF-OUT when the radio-frequency signal RF-MID increases and in which the balun 3 reduces the radio-frequency signal RF-OUT when the radio-frequency signal RF-MID decreases.
[0192] Hence, the electronic circuit 1B has characteristics in which the electronic circuit 1B reduces the radio-frequency signal RF-OUT when the signal BB-IN increases and in which the electronic circuit 1B increases the radio-frequency signal RF-OUT when the signal BB-IN decreases.
[0193] Note that the third embodiment can be combined with the second embodiment. That is, the detector circuit 4 in the electronic circuit 1B may be replaced with the detector circuit 4A (see
Fourth Embodiment
[0194] If the power of the radio-frequency signal RF-IN is not small (is sufficiently large) for the sensitivity of the detector circuit, amplification by the active balun is optional.
[0195] An electronic circuit 1C according to a fourth embodiment includes, in place of an active balun, a balun using a transformer that is a passive element.
(Overall Configuration)
[0196] Of components in the fourth embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0197]
(Configuration and Operation of Balun)
[0198] In comparison with the electronic circuit 1 according to the first embodiment (see
[0199] The balun 3C includes a primary winding L.sub.AB1 and a secondary winding L.sub.AB2 that couple to each other via an electromagnetic field. The radio-frequency signal RF-MID is input to one end of the primary winding L.sub.AB1. The other end of the primary winding L.sub.AB1 is electrically connected to the reference potential. The other end of the primary winding L.sub.AB1 may be electrically connected to a low-impedance circuit.
[0200] One end of the secondary winding L.sub.AB2 is electrically connected to the base of the transistor Q.sub.DE2 and outputs an induced radio-frequency signal RF-OUT(P) to the base of the transistor Q.sub.DE2. The other end of the secondary winding L.sub.AB2 is electrically connected to the base of the transistor Q.sub.DE1 and outputs an induced radio-frequency signal RF-OUT(N) to the base of the transistor Q.sub.DE1.
[0201] The balun 3C converts the radio-frequency signal RF-MID, which is a single ended-signal, into the radio-frequency signal RF-OUT, which refers to differential signals.
[0202] In comparison with the balun 3 (see
[0203] Note that the fourth embodiment can be combined with the second embodiment. That is, the detector circuit 4 in the electronic circuit 1C may be replaced with the detector circuit 4A (see
[0204] Furthermore, the fourth embodiment can be combined with the third embodiment. That is, the variable amplitude control circuit 2 in the electronic circuit 1C may be replaced with the variable amplitude control circuit 2B (see
Fifth Embodiment
[0205] In the first to fourth embodiments, a circuit in the stage subsequent to the balun 3 or 3C is the detector circuit 4 or 4A. However, as a circuit that malfunctions when a common mode signal is input, a differential amplifier circuit is given as an example in addition to the detector circuit 4 or 4A.
[0206] When a common mode signal is input to two input terminals of the differential amplifier circuit, bias points of a differential pair of transistors connected to the input terminals simultaneously shift in the same direction. Thus, gains of the differential pair of transistors also change along with shifts of the bias points. For example, if the bias points of the differential pair of transistors shift and both the gains of the differential pair of transistors change into a high state, the gain of the differential amplifier circuit also changes into a high state, and no signal of interest can be obtained.
[0207] An electronic circuit 1D according to a fifth embodiment deals with the above-described issue.
(Overall Configuration)
[0208] Of components in the fifth embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0209]
[0210] In comparison with the electronic circuit 1B according to the third embodiment (see
(Configuration and Operation of Differential Amplifier Circuit)
[0211] The differential amplifier circuit 5 includes transistors Q.sub.AM1 to Q.sub.AM5, resistors R.sub.AM1 to R.sub.AM3, and a transformer L.sub.AM.
[0212] The transistors Q.sub.AM1 and Q.sub.AM2 are transistors constituting a differential pair. The transistors Q.sub.AM3 to Q.sub.AM5 and the resistors R.sub.AM1 to R.sub.AM3 supply a bias to bases of the transistors Q.sub.AM1 and Q.sub.AM2.
[0213] The transistors Q.sub.AM1 and Q.sub.AM2 correspond to an example of a pair of second transistors in the present disclosure. The transistor Q.sub.AM3 corresponds to an example of third transistor in the present disclosure.
[0214] A bias current BIAS.sub.AM is supplied to one end of the resistor R.sub.AM3. The other end of the resistor R.sub.AM3 is electrically connected to a collector and a base of the transistor Q.sub.AM4. That is, the transistor Q.sub.AM4 is diode-connected. An emitter of the transistor Q.sub.AM4 is electrically connected to a collector and a base of the transistor Q.sub.AM5. That is, the transistor QAM is diode-connected. An emitter of the transistor Q.sub.AM5 is electrically connected to the reference potential.
[0215] The transistors Q.sub.AM4 and Q.sub.AM5 generate a fixed voltage. This voltage is input to a base of the transistor Q.sub.AM3.
[0216] A collector of the transistor Q.sub.AM3 is electrically connected to the power supply potential Vcc and receives a supply of power. An emitter of the transistor Q.sub.AM3 is electrically connected to a node N.sub.AM1.
[0217] One end of the resistor R.sub.AM1 is electrically connected to the node N.sub.AM1. The other end of the resistor R.sub.AM1 is electrically connected to the base of the transistor Q.sub.AM1. Thus, the transistor Q.sub.AM3 can adjust a base current of the transistor Q.sub.AM1.
[0218] One end of the resistor R.sub.AM2 is electrically connected to the node N.sub.AM1. The other end of the resistor R.sub.AM2 is electrically connected to the base of the transistor Q.sub.AM2. Thus, the transistor Q.sub.AM3 can adjust a base current of the transistor Q.sub.AM2.
[0219] The radio-frequency signals RF-OUT(P) and RF-OUT(N) are respectively input to the base of the transistor Q.sub.AM2 and the base of the transistor Q.sub.AM1.
[0220] A primary winding of the transformer L.sub.AM includes a winding L.sub.AM1P and a winding L.sub.AM2P that are connected in series.
[0221] One end of the winding L.sub.AM1P is electrically connected to a collector of the transistor Q.sub.AM1. The other end of the winding L.sub.AM1P is electrically connected to one end of the winding L.sub.AM2P and is also electrically connected to the power supply potential Vcc. The other end of the winding L.sub.AM2P is electrically connected to a collector of the transistor Q.sub.AM2.
[0222] A secondary winding of the transformer L.sub.AM includes a winding L.sub.AM1S and a winding L.sub.AM2S that are connected in series and couples to the primary winding of the transformer L.sub.AM via an electromagnetic field.
[0223] One end of the winding L.sub.AM1S is electrically connected to the reference potential. The other end of the winding L.sub.AM1S is electrically connected to one end of the winding L.sub.AM2S. From the other end of the winding L.sub.AM2S, a radio-frequency signal RF-AM, which is a single-ended signal, is output.
[0224] Even if the signal BB-IN is input from the balun 3 to the differential amplifier circuit 5, the signal BB-IN is input as differential signals. Hence, signals BB-IN that are differential signals pass through the resistors R.sub.AM1 and R.sub.AM2, and combine and are consumed at the node N.sub.AM1 that is a virtual ground point.
[0225] Furthermore, even if the signals BB-IN that are differential signals are input to the respective bases of the transistors Q.sub.AM1 and Q.sub.AM2, when a bias point of one transistor of the transistors Q.sub.AM1 and Q.sub.AM2 increases, a bias point of the other transistor of the transistors Q.sub.AM1 and Q.sub.AM2 decreases. That is, when the gain of one transistor of the transistors Q.sub.AM1 and Q.sub.AM2 increases, the gain of the other transistor of the transistors Q.sub.AM1 and Q.sub.AM2 decreases. Hence, in the differential amplifier circuit 5, as a whole, variations in the gains of the transistors Q.sub.AM1 and Q.sub.AM2 are cancelled out, and a stable gain can be maintained.
[0226] In the electronic circuit 1D, even if the frequency f.sub.BB-MAX, which is the maximum frequency of the frequency component of the signal BB-IN, is not less than 1% of the frequency f.sub.RF, a variation in gain of the differential amplifier circuit 5 can be reduced.
[0227] Note that the fifth embodiment can be combined with the first embodiment. That is, the variable amplitude control circuit 2B in the electronic circuit 1D may be replaced with the variable amplitude control circuit 2 (see
[0228] Furthermore, the fifth embodiment can be combined with the fourth embodiment. That is, the balun 3 in the electronic circuit 1D may be replaced with the balun 3C.
[0229] Furthermore, although the differential amplifier circuit 5 outputs the radio-frequency signal RF-AM, which is a single-ended signal, the present disclosure is not limited to this. The differential amplifier circuit 5 may omit the transformer L.sub.AM and output radio-frequency signals, which are differential signals.
[0230] Furthermore, although, in the differential amplifier circuit 5, one transistor Q.sub.AM3 supplies a bias to the bases of the transistors Q.sub.AM1 and Q.sub.AM2, the present disclosure is not limited to this. In the differential amplifier circuit 5, two transistors may supply biases to the respective bases of the transistors Q.sub.AM1 and Q.sub.AM2.
Sixth Embodiment
[0231] Of components in a sixth embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0232]
[0233] A Doherty amplifier circuit 10 includes a 90-hybrid circuit 11, a carrier amplifier 12, a peaking amplifier 13, a coupler 14, a saturation detection circuits 15 and 16, and a control circuit 17.
[0234] Although the number of stages in the Doherty amplifier circuit 10 is one, the present disclosure is not limited to this. The number of stages in the Doherty amplifier circuit 10 may be two or more. If a case where the number of stages in the Doherty amplifier circuit 10 is two or more, it is desirable that the carrier amplifier 12 and the peaking amplifier 13 be at a final stage.
[0235] The 90-hybrid circuit 11 splits an input radio-frequency signal RF.sub.IN into radio-frequency signals RF.sub.1 and RF.sub.5 that are different from each other in phase by about 90, outputs the radio-frequency signal RF.sub.1 to the carrier amplifier 12, and outputs the radio-frequency signal RF.sub.5 to the peaking amplifier 13. Note that about 90 includes not only a phase of 90 but also a phase of 90+45.
[0236] The radio-frequency signal RF.sub.IN corresponds to an example of fourth radio-frequency signal in the present disclosure. The radio-frequency signal RF.sub.1 corresponds to an example of fifth radio-frequency signal in the present disclosure. The radio-frequency signal RF.sub.5 corresponds to an example of sixth radio-frequency signal in the present disclosure.
[0237] An example is given in which the phase of the radio-frequency signal RF.sub.5 is delayed by 90 with respect to the radio-frequency signal RF.sub.1. An example is given in which the power of the radio-frequency signal RF.sub.1 and the power of the radio-frequency signal RF.sub.5 are the same.
[0238] The carrier amplifier 12 includes a variable amplitude control circuit 21, a balun 22, and a differential amplifier circuit 23.
[0239] The carrier amplifier 12 has a configuration similar to that of the electronic circuit 1D according to the fifth embodiment (see
[0240] A circuit configuration of the variable amplitude control circuit 21 is similar to that of the variable amplitude control circuit 2 (see
[0241] A circuit configuration of the balun 22 is similar to that of the balun 3 (see
[0242] A circuit configuration of the differential amplifier circuit 23 is similar to that of the differential amplifier circuit 5 (see
[0243] The variable amplitude control circuit 21 controls an amplitude of the radio-frequency signal RF.sub.1 in accordance with a signal BB-IN.sub.1 input from the control circuit 17 and outputs a radio-frequency signal RF.sub.2 to the balun 22.
[0244] The balun 22 converts the radio-frequency signal RF.sub.2 into differential signals and outputs a pair of radio-frequency signals RF.sub.3, which are differential signals, to the differential amplifier circuit 23.
[0245] The differential amplifier circuit 23 amplifies the pair of radio-frequency signals RF.sub.3 and outputs a pair of radio-frequency signals RF.sub.4, which are differential signals, to the coupler 14.
[0246] The peaking amplifier 13 includes a variable amplitude control circuit 31, a balun 32, and a differential amplifier circuit 33.
[0247] The peaking amplifier 13 has a configuration similar to that of the electronic circuit 1D according to the fifth embodiment (see
[0248] A circuit configuration of the variable amplitude control circuit 31 is similar to that of the variable amplitude control circuit 2 (see
[0249] A circuit configuration of the balun 32 is similar to that of the balun 3 (see
[0250] A circuit configuration of the differential amplifier circuit 33 is similar to that of the differential amplifier circuit 5 (see
[0251] The variable amplitude control circuit 31 controls an amplitude of the radio-frequency signal RF.sub.5 in accordance with a signal BB-IN.sub.2 input from the control circuit 17 and outputs a radio-frequency signal RF.sub.6 to the balun 32.
[0252] The balun 32 converts the radio-frequency signal RF.sub.6 into differential signals and outputs a pair of radio-frequency signals RF.sub.7, which are differential signals, to the differential amplifier circuit 33.
[0253] The differential amplifier circuit 33 amplifies the pair of radio-frequency signals RF.sub.7 and outputs a pair of radio-frequency signals RF.sub.8, which are differential signals, to the coupler 14.
[0254] Note that, although both the carrier amplifier 12 and the peaking amplifier 13 include the respective variable amplitude control circuits and the respective baluns, the present disclosure is not limited to this. At least one of the carrier amplifier 12 and the peaking amplifier 13 may include a variable amplitude control circuit and a balun.
[0255] The coupler 14 couples the pair of radio-frequency signals RF.sub.4 and the pair of radio-frequency signals RF.sub.8 and outputs a radio-frequency signal RF.sub.OUT, which is a single-ended signal.
[0256] The saturation detection circuit 15 outputs, in accordance with an amplifier transistor itself or a bias circuit, a saturation signal S.sub.SAT1 representing the degree of saturation of the differential amplifier circuit 23 to the control circuit 17.
[0257] The saturation detection circuit 16 outputs, in accordance with an amplifier transistor itself or a bias circuit, a saturation signal S.sub.SAT2 representing the degree of saturation of the differential amplifier circuit 33 to the control circuit 17.
[0258] The saturation signal S.sub.SAT1 or the saturation signal S.sub.SAT2 corresponds to an example of saturation signal in the present disclosure.
[0259] The control circuit 17 respectively outputs the signals BB-IN.sub.1 and BB-IN.sub.2 to the variable amplitude control circuit 21 and the variable amplitude control circuit 31 in accordance with the saturation signals S.sub.SAT1 and S.sub.SAT2, and at least one of envelope signals of the radio-frequency signal RF.sub.IN, the radio-frequency signal RF.sub.1, and the radio-frequency signal RF.sub.5.
[0260] Each of the signals BB-IN.sub.1 and BB-IN.sub.2 corresponds to an example of control signal in the present disclosure.
[0261] The Doherty amplifier circuit 10 controls amplitudes of the radio-frequency signals RF.sub.2 and RF.sub.6 in accordance with the signals BB-IN and BB-IN.sub.2, thereby making it possible to reduce distortions in the pair of radio-frequency signals RF.sub.4 and the pair of radio-frequency signals RF.sub.8.
[0262] U.S. Pat. No. 10,978,999 discloses a technique in which the gain of a variable gain amplifier in which all signals are single-ended signals is changed. However, when the variable gain amplifier is configured in which all signals are single-ended signals, in some cases, a BB signal leaks and is input to an amplifier stage, and a bias point in the amplifier stage varies, resulting in the occurrence of a distortion in an output signal.
[0263] On the other hand, when the Doherty amplifier circuit 10 is configured as described above, even if the signals BB-IN.sub.1 and BB-IN.sub.2 leak, the signals BB-IN.sub.1 and BB-IN.sub.2 are input to the differential amplifier circuits 23 and 33 as differential signals. Hence, in the Doherty amplifier circuit 10, distortions in the pair of radio-frequency signals RF.sub.4 and the pair of radio-frequency signals RF& can be reduced by the effect of attenuating the signals BB-IN.sub.1 and BB-IN.sub.2 by resistors in bias circuit sections in the differential amplifier circuits 23 and 33 and the effect of cancelling out gains of a differential pair of transistors.
Seventh Embodiment
[0264] Of components in a seventh embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0265]
[0266] A Doherty amplifier circuit 40 includes the electronic circuit 1, the 90-hybrid circuit 11, baluns 41, 44, 46, and 49, a first-stage carrier amplifier 42, an intermediate-stage carrier amplifier 43, a final-stage carrier amplifier 45, a first-stage peaking amplifier 47, an intermediate-stage peaking amplifier 48, a final-stage peaking amplifier 50, bias circuits 51 to 56, the coupler 14, and an attenuator 81.
[0267] Although the number of stages in the Doherty amplifier circuit 40 is three, the present disclosure is not limited to this. The number of stages in the Doherty amplifier circuit 40 may be two or less or may be four or more.
[0268] Each of the carrier amplifiers 42, 43 and 45, and the peaking amplifiers 47, 48, and 50 is a differential amplifier.
[0269] The carrier amplifiers 42, 43, and 45 correspond to an example of at least one-stage carrier amplifier in the present disclosure. The peaking amplifiers 47, 48, and 50 correspond to an example of at least one-stage peaking amplifier in the present disclosure.
[0270] The 90-hybrid circuit 11 splits a radio-frequency signal RF.sub.IN into radio-frequency signals RF.sub.11 and RF.sub.31 that are different from each other in phase by about 90, outputs the radio-frequency signal RF.sub.11 to one end of a primary winding of the balun 41, and outputs the radio-frequency signal RF.sub.31 to one end of a primary winding of the balun 46. The other end of the primary winding of the balun 41 and the other end of the primary winding of the balun 46 are electrically connected to the reference potential.
[0271] The radio-frequency signal RF.sub.IN corresponds to an example of fourth radio-frequency signal in the present disclosure. The radio-frequency signal RF.sub.11 corresponds to an example of fifth radio-frequency signal in the present disclosure. The radio-frequency signal RF.sub.31 corresponds to an example of sixth radio-frequency signal in the present disclosure.
[0272] The balun 41 outputs radio-frequency signals RF.sub.12 and RF.sub.13, which are differential signals, from both respective ends of its secondary winding in accordance with the input radio-frequency signal RF.sub.11.
[0273] The balun 46 outputs radio-frequency signals RF.sub.32 and RF.sub.33, which are differential signals, from both respective ends of its secondary winding in accordance with the input radio-frequency signal RF.sub.31.
[0274] The bias circuit 51 supplies a bias to the carrier amplifier 42. A first amplifier 61 in the carrier amplifier 42 outputs a radio-frequency signal RF.sub.14 obtained by amplifying the radio-frequency signal RF.sub.12 to the carrier amplifier 43. A second amplifier 62 in the carrier amplifier 42 outputs a radio-frequency signal RF.sub.15 obtained by amplifying the radio-frequency signal RF.sub.13 to the carrier amplifier 43.
[0275] The bias circuit 52 supplies a bias to the carrier amplifier 43. A first amplifier 63 in the carrier amplifier 43 outputs a radio-frequency signal RF.sub.16 obtained by amplifying the radio-frequency signal RF.sub.14 to one end of a primary winding of the balun 44. A second amplifier 64 in the carrier amplifier 43 outputs a radio-frequency signal RF.sub.17 obtained by amplifying the radio-frequency signal RF.sub.15 to the other end of the primary winding of the balun 44.
[0276] The balun 44 outputs radio-frequency signals RF.sub.18 and RF.sub.19, which are differential signals, from both respective ends of its secondary winding in accordance with the input radio-frequency signals RF.sub.16 and RF.sub.17.
[0277] The bias circuit 53 supplies a bias to the carrier amplifier 45. A first amplifier 65 in the carrier amplifier 45 outputs a radio-frequency signal RF.sub.20 obtained by amplifying the radio-frequency signal RF.sub.18 to one end of a first winding on a primary side of the coupler 14. A second amplifier 66 in the carrier amplifier 45 outputs a radio-frequency signal RF.sub.21 obtained by amplifying the radio-frequency signal RF.sub.19 to the other end of the first winding on the primary side of the coupler 14.
[0278] The bias circuit 54 supplies a bias to the peaking amplifier 47. A first amplifier 71 in the peaking amplifier 47 outputs a radio-frequency signal RF.sub.34 obtained by amplifying the radio-frequency signal RF.sub.32 to the peaking amplifier 48. A second amplifier 72 in the peaking amplifier 47 outputs a radio-frequency signal RF.sub.35 obtained by amplifying the radio-frequency signal RF.sub.33 to the peaking amplifier 48.
[0279] The bias circuit 55 supplies a bias to the peaking amplifier 48. A first amplifier 73 in the peaking amplifier 48 outputs a radio-frequency signal RF.sub.36 obtained by amplifying the radio-frequency signal RF.sub.34 to one end of a primary winding of the balun 49. A second amplifier 74 in the peaking amplifier 48 outputs a radio-frequency signal RF.sub.37 obtained by amplifying the radio-frequency signal RF.sub.35 to the other end of the primary winding of the balun 49.
[0280] The balun 49 outputs radio-frequency signals RF.sub.38 and RF.sub.39, which are a pair of differential signals, from both respective ends of its secondary winding in accordance with the input radio-frequency signals RF.sub.36 and RF.sub.37.
[0281] The bias circuit 56 supplies a bias to the peaking amplifier 50. A first amplifier 75 in the peaking amplifier 50 outputs a radio-frequency signal RF.sub.40 obtained by amplifying the radio-frequency signal RF.sub.38 to one end of a second winding on the primary side of the coupler 14. A second amplifier 76 in the peaking amplifier 50 outputs a radio-frequency signal RF.sub.41 obtained by amplifying the radio-frequency signal RF.sub.39 to the other end of the second winding on the primary side of the coupler 14.
[0282] The bias circuits 54, 55, and 56 correspond to an example of at least one bias circuit in the present disclosure.
[0283] The coupler 14 couples the radio-frequency signals RF.sub.20 and RF.sub.21 and the radio-frequency signals RF.sub.40 and RF.sub.41 and outputs a radio-frequency signal RF.sub.OUT.
[0284] The radio-frequency signal RF.sub.IN is input to the attenuator 81. In place of the radio-frequency signal RF.sub.IN, the radio-frequency signal RF.sub.11 or RF.sub.31 may be input to the attenuator 81. The attenuator 81 outputs a radio-frequency signal RF.sub.51 obtained by attenuating the radio-frequency signal RF.sub.IN (or alternatively, the radio-frequency signal RF.sub.11 or RF.sub.31) to the electronic circuit 1.
[0285] The attenuator 81 may be a variable attenuator that can adjust an attenuation in accordance with an external control signal. The attenuator 81 may be omitted.
[0286] The electronic circuit 1 includes the variable amplitude control circuit 2, the balun 3, and the detector circuit 4. The electronic circuit 1 may include the variable amplitude control circuit 2B (see
[0287] The radio-frequency signal RF.sub.51 is input from the attenuator 81 to the variable amplitude control circuit 2 in the electronic circuit 1.
[0288] In place of the radio-frequency signal RF.sub.51, the radio-frequency signal RF.sub.IN, RF.sub.11, or RF.sub.31 may be input to the variable amplitude control circuit 2 in the electronic circuit 1.
[0289] In the seventh embodiment, the radio-frequency signal RF.sub.51 corresponds to the radio-frequency signal RF-IN (see
[0290] A saturation signal S.sub.SAT is input from the bias circuit 53 to the variable amplitude control circuit 2 in the electronic circuit 1. The saturation signal S.sub.SAT may be input from the bias circuit 56.
[0291] The saturation signal S.sub.SAT corresponds to an example of saturation signal in the present disclosure.
[0292] In the seventh embodiment, the saturation signal S.sub.SAT corresponds to the signal BB-IN (see
[0293] The variable amplitude control circuit 2 outputs, to the balun 3, a radio-frequency signal RF-MID obtained by controlling, in accordance with the saturation signal S.sub.SAT, an amplitude of the radio-frequency signal RF.sub.51 (or alternatively, the radio-frequency signal RF.sub.IN, RF.sub.11, or RF.sub.31, or a signal obtained by the attenuator 81 attenuating the radio-frequency signal RF.sub.IN, RF.sub.11, or RF.sub.31).
[0294] The balun 3 outputs radio-frequency signals RF-OUT(P) and RF-OUT(N), which are differential signals into which the radio-frequency signal RF-MID has been converted, to the detector circuit 4.
[0295] The detector circuit 4 outputs a detected signal S.sub.DET obtained through detection of the radio-frequency signals RF-OUT(P) and RF-OUT(N) to the bias circuits 54 to 56.
[0296] The bias circuit 54 supplies a bias to the peaking amplifier 47 in accordance with the detected signal S.sub.DET. The bias circuit 55 supplies a bias to the peaking amplifier 48 in accordance with the detected signal S.sub.DET. The bias circuit 56 supplies a bias to the peaking amplifier 50 in accordance with the detected signal S.sub.DET.
[0297] Incidentally, it can also be considered that the variable amplitude control circuit 2 is provided as a differential circuit and is disposed between the balun 3 and the detector circuit 4.
[0298] However, it is desirable that the variable amplitude control circuit 2 be a single-ended circuit and the detector circuit 4 be a differential circuit as illustrated in
[0299] It is desirable that the detector circuit 4 be a differential circuit to implement fast detection. This is because an output signal of the detector circuit 4 is a single-ended signal. Hence, since the detector circuit 4 is a differential circuit, an output of the detector circuit 4 is a virtual ground point for a radio-frequency signal, and no large capacitor that results in time delays is necessary. In other words, the detector circuit 4 is excellent in frequency characteristics and also operates for a signal with a significantly lower frequency than a carrier frequency.
[0300] The detector circuit 4 can operate fast, whereas another characteristic of the detector circuit 4 is that the detector circuit 4 often outputting a large error if a common mode signal component (in-phase component) is input to two input terminals.
[0301] A case is examined where the variable amplitude control circuit 2 is disposed between the balun 3 and the detector circuit 4. In the variable amplitude control circuit 2, a control signal is basically a single-ended signal. For this reason, when the control signal is caused to operate fast, part of the control signal is also output to two output terminals of the variable amplitude control circuit 2 as a common mode signal component. When that signal is input to the detector circuit 4, unexpected operation of the detector circuit 4 is caused.
[0302] On the other hand, when the variable amplitude control circuit 2 is disposed in a stage preceding the balun 3 as illustrated in
Eighth Embodiment
[0303] Of components in an eighth embodiment, components that are the same as components in the other embodiments are denoted by the same reference signs, and a description thereof is omitted.
[0304]
[0305] An electronic circuit 1E according to the eighth embodiment is an electronic circuit obtained by modifying the electronic circuit 1A according to the second embodiment (see
[0306] The electronic circuit 1E includes a variable amplitude control circuit 6 and a differential amplifier 7. The variable amplitude control circuit 6 corresponds to an integrated combination of the variable amplitude control circuit 2 and the balun 3.
[0307] The variable amplitude control circuit 6 includes a transistor Q.sub.1, a transistor Q.sub.2, a transistor Q.sub.7, a transistor Q.sub.8, a transistor Q.sub.9, and a transistor Q.sub.F1. Furthermore, the variable amplitude control circuit 6 includes a resistor R.sub.B1, a resistor R.sub.B2, a resistor R.sub.C1, a resistor R.sub.C2, and a resistor RF.sub.1. Furthermore, the variable amplitude control circuit 6 includes a capacitor C.sub.B1, a capacitor C.sub.B2, a capacitor C.sub.F1, and a constant current source I.sub.SET.
[0308] The transistor Q.sub.1, the resistor R.sub.B1, and the capacitor C.sub.B1 constitute an amplifier section and correspond to the transistor Q.sub.AT1, the resistor R.sub.AT1, and the capacitor C.sub.AT1 in the variable amplitude control circuit 2 (see
[0309] The transistors Q.sub.1 and Q.sub.2 are transistors constituting a differential pair. The transistors Q.sub.7 to Q.sub.9 are transistors that supply a bias to the transistor Q.sub.1 and the transistor Q.sub.2.
[0310] One end of the resistor Ra is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.C1 is electrically connected to a node N.sub.1. A collector of the transistor Q.sub.1 is electrically connected to the node N.sub.1. The collector of the transistor Q.sub.1 is electrically connected to the power supply potential Vcc via the resistor R.sub.C1 and receives a supply of power.
[0311] The node N.sub.1 is an output node of the transistor Q.sub.1.
[0312] One end of the resistor R.sub.B1 is electrically connected to the node N.sub.1. The other end of the resistor R.sub.B1 is electrically connected to a base of the transistor Q.sub.1. The base of the transistor Q.sub.1 is electrically connected to the power supply potential Vcc via the resistors R.sub.C1 and R.sub.B1 and is biased.
[0313] The base of the transistor Q.sub.1 is electrically connected to an input terminal 6a via the capacitor C.sub.B1, which is a DC cut capacitor. A radio-frequency signal RF-IN, which is a single-ended signal, is input to the input terminal 6a.
[0314] One end of the resistor R.sub.C2 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.C2 is electrically connected to a node N.sub.2. A collector of the transistor Q.sub.2 is electrically connected to the node N.sub.2. The collector of the transistor Q.sub.2 is electrically connected to the power supply potential Vcc via the resistor R.sub.C2 and receives a supply of power.
[0315] The node N.sub.2 is an output node of the transistor Q.sub.2.
[0316] One end of the resistor R.sub.B2 is electrically connected to the node N.sub.2. The other end of the resistor R.sub.B2 is electrically connected to a base of the transistor Q.sub.2. The base of the transistor Q.sub.2 is electrically connected to the power supply potential Vcc via the resistors R.sub.C2 and R.sub.B2 and is biased. The base of the transistor Q.sub.2 is electrically connected to the reference potential via the capacitor C.sub.B2. The transistor Q.sub.2 is base-grounded by the capacitor C.sub.B2.
[0317] Thus, the transistor Q.sub.1 and the transistor Q.sub.2 amplify the radio-frequency signal RF-IN and output a radio-frequency signal RF-MID (P) and a radio-frequency signal RF-MID (N) to the differential amplifier 7.
[0318] A collector and a base of the transistor Q.sub.7 are electrically connected to a node N.sub.3. That is, the transistor Q.sub.7 is diode-connected. An emitter of the transistor Q.sub.7 is electrically connected to a node N.sub.4. A collector and a base of the transistor Q.sub.8 are electrically connected to the node N.sub.4. That is, the transistor Q.sub.8 is diode-connected. An emitter of the transistor Q.sub.8 is electrically connected to the reference potential.
[0319] The constant current source I.sub.SET outputs a constant current to the node N.sub.3. This constant current flows to the transistor Q.sub.7 and the transistor Q.sub.8. The transistor Q.sub.7 and the transistor Q.sub.8 generate a fixed voltage based on the constant current. This voltage is a voltage of the node N.sub.3. The voltage of the node N.sub.3 is hereinafter referred to as a voltage 2Vbe.
[0320] An emitter of the transistor Q.sub.9 is electrically connected to the reference potential. A base of the transistor Q.sub.9 is electrically connected to the node N.sub.4. That is, the transistor Q.sub.8 and the transistor Q.sub.9 are connected so as to establish a current-mirror connection. A collector of the transistor Q.sub.9 is electrically connected to an emitter of the transistor Q.sub.1 and an emitter of the transistor Q.sub.2. The transistor Q.sub.9 passes emitter currents of the transistor Q.sub.1 and the transistor Q.sub.2 at all times.
[0321] One end of the resistor R.sub.F1 is electrically connected to the emitter of the transistor Q.sub.1 and the emitter of the transistor Q.sub.2. The other end of the resistor R.sub.F1 is electrically connected to a node N.sub.5. One end of the capacitor Cri is electrically connected to the node N.sub.5. The other end of the capacitor C.sub.F1 is electrically connected to the reference potential.
[0322] A collector of the transistor Q.sub.F1 is electrically connected to the node N.sub.5. An emitter of the transistor Q.sub.F1 is electrically connected to the reference potential. A base of the transistor Q.sub.F1 is electrically connected to an input terminal 6b. A signal BB-IN is input to the input terminal 6b.
[0323] The transistor Q.sub.F1 increases or decreases the emitter currents of the transistor Q.sub.1 and the transistor Q.sub.2 in accordance with the signal BB-IN.
[0324] The differential amplifier 7 includes transistors Q.sub.3 to Q.sub.6, and transistors Q.sub.10 to Q.sub.12. Furthermore, the differential amplifier 7 includes a resistor R.sub.B3, a resistor R.sub.B4, a resistor R.sub.C3, and a resistor R.sub.C4. Furthermore, the differential amplifier 7 includes a capacitor C.sub.B3, a capacitor C.sub.B4, a capacitor C.sub.O1, and a capacitor C.sub.O2.
[0325] The transistors Q.sub.3 and Q.sub.4 are transistors constituting a differential pair. The transistors Q.sub.5 and Q.sub.6 are output transistors. The transistors Q.sub.10 to Q.sub.12 are transistors that supply a bias to the transistors Q.sub.3 to Q.sub.6.
[0326] One end of the resistor R.sub.C3 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.C3 is electrically connected to a node N.sub.11. A collector of the transistor Q.sub.3 is electrically connected to the node N.sub.11. The collector of the transistor Q.sub.3 is electrically connected to the power supply potential Vcc via the resistor R.sub.C3 and receives a supply of power.
[0327] The node Nu is an output node of the transistor Q.sub.3.
[0328] One end of the resistor R.sub.B3 is electrically connected to the node N.sub.3. The other end of the resistor R.sub.B3 is electrically connected to a base of the transistor Q.sub.3. The base of the transistor Q.sub.3 receives an input of the voltage 2Vbe via the resistor R.sub.B3 and is biased. The radio-frequency signal RF-MID (P) is input from the variable amplitude control circuit 6 to the base of the transistor Q.sub.3 via the capacitor C.sub.B3, which is a DC cut capacitor.
[0329] One end of the resistor R.sub.C4 is electrically connected to the power supply potential Vcc. The other end of the resistor R.sub.C4 is electrically connected to a node N.sub.12. A collector of the transistor Q.sub.4 is electrically connected to the node N.sub.12. The collector of the transistor Q.sub.4 is electrically connected to the power supply potential Vcc via the resistor R.sub.C4 and receives a supply of power.
[0330] The node N.sub.12 is an output node of the transistor Q.sub.4.
[0331] One end of the resistor R.sub.B4 is electrically connected to the node N.sub.3. The other end of the resistor R.sub.B4 is electrically connected to a base of the transistor Q.sub.4. The base of the transistor Q.sub.4 receives an input of the voltage 2Vbe via the resistor R.sub.B4 and is biased. The radio-frequency signal RF-MID (N) is input from the variable amplitude control circuit 6 to the base of the transistor Q.sub.4 via the capacitor C.sub.B4, which is a DC cut capacitor.
[0332] A collector of the transistor Q.sub.5 is electrically connected to the power supply potential Vcc and receives a supply of power. A base of the transistor Q.sub.5 is electrically connected to the node N.sub.11. An emitter of the transistor Q.sub.5 is electrically connected to a node N.sub.13.
[0333] The node N.sub.13 is an output node of the transistor Q.sub.5.
[0334] A collector of the transistor Q.sub.6 is electrically connected to the power supply potential Vcc and receives a supply of power. A base of the transistor Q.sub.6 is electrically connected to the node N.sub.12. An emitter of the transistor Q.sub.6 is electrically connected to a node N.sub.14.
[0335] The node N.sub.14 is an output node of the transistor Q.sub.6.
[0336] An emitter of the transistor Q.sub.10 is electrically connected to the reference potential. A base of the transistor Q.sub.10 is electrically connected to the node N.sub.4. That is, the transistor Q.sub.8 and the transistor Q.sub.10 are connected so as to establish a current-mirror connection. A collector of the transistor Q.sub.10 is electrically connected to an emitter of the transistor Q.sub.3 and an emitter of the transistor Q.sub.4. The transistor Q.sub.10 passes emitter currents of the transistor Q.sub.3 and the transistor Q.sub.4 at all times.
[0337] An emitter of the transistor Qu is electrically connected to the reference potential. A base of the transistor Q.sub.11 is electrically connected to the node N.sub.4. That is, the transistor Q.sub.8 and the transistor Q.sub.11 are connected so as to establish a current-mirror connection. A collector of the transistor On is electrically connected to the node N.sub.13. The transistor On passes an emitter current of the transistor Q.sub.5 at all times.
[0338] An emitter of the transistor Q.sub.12 is electrically connected to the reference potential. A base of the transistor Q.sub.12 is electrically connected to the node N.sub.4. That is, the transistor Q.sub.8 and the transistor Q.sub.12 are connected so as to establish a current-mirror connection. A collector of the transistor Q.sub.12 is electrically connected to the node N.sub.14. The transistor Q.sub.12 passes an emitter current of the transistor Q.sub.6 at all times.
[0339] One end of the capacitor C.sub.O1, which is a DC cut capacitor, is electrically connected to the node N.sub.13. The other end of the capacitor C.sub.O1 is electrically connected to a terminal 7a. The transistor Q.sub.5 outputs a radio-frequency signal RF-OUT(P) from the terminal 7a.
[0340] One end of the capacitor Coz, which is a DC cut capacitor, is electrically connected to the node N.sub.14. The other end of the capacitor C.sub.O2 is electrically connected to a terminal 7b. The transistor Q.sub.6 outputs a radio-frequency signal RF-OUT(N) from the terminal 7b.
Effects
(1)
[0341] In the electronic circuit 1A according to the second embodiment (see
[0342] On the other hand, in the electronic circuit 1E according to the eighth embodiment, when the signal BB-IN is input, voltage drops occur by the same amount across the resistor R.sub.C1 and the resistor R.sub.C2. That is, in the radio-frequency signal RF-MID (P) and the radio-frequency signal RF-MID (N), an in-phase voltage drop occurs. The differential amplifier 7 does not amplify the in-phase voltage drop and removes it. Hence, the electronic circuit 1E can keep the signal BB-IN from leaking into the radio-frequency signal RF-OUT(P) and the radio-frequency signal RF-OUT(N).
[0343] Thus, the electronic circuit 1E can be used even if a circuit in a stage subsequent to the electronic circuit 1E is a circuit that is not able to permit leakage of differential signals.
(2)
[0344] In the electronic circuit 1A according to the second embodiment, the base of the transistor Q.sub.AB1 is biased from the power supply potential Vcc via the resistor R.sub.AB3 and the resistor R.sub.AB1. The base of the transistor Q.sub.AB3 is biased from the power supply potential Vcc via the resistor R.sub.AB1. That is, the resistor R.sub.AB1 is shared between a base bias of the transistor Q.sub.AB1 and a base bias of the transistor Q.sub.AB3, which is an output transistor.
[0345] In the electronic circuit 1A according to the second embodiment, the signal BB-IN can leak into the radio-frequency signal RF-MID. The radio-frequency signal RF-MID is input to the base of the transistor Q.sub.AB1. Since the resistor R.sub.AB1 is electrically connected to the base of the transistor Q.sub.AB1, a voltage or current of the resistor R.sub.AB1 is affected by a signal BB-IN that has leaked and varies. Thus, a base voltage or base current of the transistor Q.sub.AB3 varies. Hence, in the electronic circuit 1A, the signal BB-IN that has leaked is amplified by the transistor Q.sub.AB3 and the transistor Q.sub.AB4 (the gain for the leaked signal is large) and leaks into the radio-frequency signal RF-OUT(P) and the radio-frequency signal RF-OUT(N).
[0346] On the other hand, in the electronic circuit 1E according to the eighth embodiment, the base of the transistor Q.sub.3 is biased from the node N.sub.3 (voltage 2Vbe) via the resistor R.sub.B3. The base of the transistor Q.sub.5, which is an output transistor, is biased from the power supply potential Vcc via the resistor R.sub.C3. That is, a base bias of the transistor Q.sub.3 and a base bias of the transistor Q.sub.5 are completely isolated from each other.
[0347] Similarly, the base of the transistor Q.sub.4 is biased from the node N.sub.3 (voltage 2Vbe) via the resistor R.sub.B4. The base of the transistor Q.sub.6, which is an output transistor, is biased from the power supply potential Vcc via the resistor R.sub.C4. That is, a base bias of the transistor Q.sub.4 and a base bias of the transistor Q.sub.6 are completely isolated from each other.
[0348] The radio-frequency signal RF-MID (P) is input to the base of the transistor Q.sub.3. Since the base bias of the transistor Q.sub.3 and the base bias of the transistor Q.sub.5 are completely isolated from each other, a voltage or current of the resistor R.sub.C3 is not affected even if the signal BB-IN leaks into the radio-frequency signal RF-MID (P).
[0349] Similarly, the radio-frequency signal RF-MID (N) is input to the base of the transistor Q.sub.4. Since the base bias of the transistor Q.sub.4 and the base bias of the transistor Q.sub.6 are completely isolated from each other, a voltage or current of the resistor R.sub.C4 is not affected even if the signal BB-IN leaks into the radio-frequency signal RF-MID (N).
[0350] Thus, the electronic circuit 1E can keep the signal BB-IN from being amplified (can reduce the gain for the leaked signal) even if the signal BB-IN leaks into the radio-frequency signal RF-MID (P) and the radio-frequency signal RF-MID (N).
[0351] The above-described embodiments are intended to facilitate understanding of the present disclosure but are not intended for a limited interpretation of the present disclosure. The present disclosure can be changed or improved without necessarily departing from the gist thereof and also encompasses equivalents thereof.
REFERENCE SIGNS LIST
[0352] 1, 1A, 1B, 1C, 1D, 1E electronic circuit [0353] 2, 6, 2B, 2I, 31 variable amplitude control circuit [0354] 3, 3C, 22, 32, 41, 44, 46, 49 balun [0355] 4, 4A detector circuit [0356] 5, 23, 33 differential amplifier circuit [0357] 7 differential amplifier [0358] 10, 40 Doherty amplifier circuit [0359] 11 90-hybrid circuit [0360] 12, 42, 43, 45 carrier amplifier [0361] 13, 47, 48, 50 peaking amplifier [0362] 14 coupler [0363] 15, 16 saturation detection circuit [0364] 17 control circuit [0365] 51, 52, 53, 54, 55, 56 bias circuit [0366] 81 attenuator