Lumped compensated outphasing power combiner

Abstract

A power combiner for an outphasing amplifier system comprises an output terminal, a first input terminal, a first inductor, and a first capacitor, wherein the first input terminal is connected to ground via the first inductor and the first input terminal is connected to the output terminal via the first capacitor. The power combiner further comprises a second input terminal, a second capacitor, and a second inductor, wherein the second input terminal is connected to ground via the second capacitor and the second input terminal is connected to the output terminal via the second inductor. The first capacitor can have a same capacitance as the second capacitor and the first inductor has a same inductance as the second inductor.

Claims

1. A power combiner for an outphasing amplifier system, comprising an output terminal; a first input terminal, a first inductor, and a first capacitor, wherein the first input terminal is connected to ground via the first inductor and the first input terminal is connected to the output terminal via the first capacitor; and a second input terminal, a second capacitor, and a second inductor, wherein the second input terminal is connected to ground via the second capacitor and the second input terminal is connected to the output terminal via the second inductor, wherein the second capacitor has a capacitance C.sub.tot substantially equal to a capacitance of a parallel combination of a capacitor having a capacitance C.sub.m equal to the capacitance of the first capacitor and a compensation capacitance C.sub.comp, and the first inductor has an inductance L.sub.tot substantially equal to an inductance of a parallel combination of an inductor having an inductance L.sub.m equal to the inductance of the second inductor and a compensation inductance L.sub.comp.

2. The power combiner of claim 1, wherein the first input terminal is further connected to ground via a first compensation impedance, and the second input terminal is further connected to ground via a second compensation impedance.

3. The power combiner of claim 2, wherein the first compensation impedance comprises a capacitance and the second compensation impedance comprises a inductor, or the first compensation impedance comprises a inductor and the second compensation impedance comprises a capacitance.

4. The power combiner of claim 1, wherein at least one of the first compensation impedance and the second compensation impedance is adjustable.

5. A power combiner for an outphasing amplifier system, comprising an output terminal; a first input terminal, a first inductor, and a first capacitor, wherein the first input terminal is connected to ground via the first inductor and the first input terminal is connected to the output terminal via the first capacitor; and a second input terminal, a second capacitor, and a second inductor, wherein the second input terminal is connected to ground via the second capacitor and the second input terminal is connected to the output terminal via the second inductor, wherein the first capacitor and the first inductor are configured to cause a phase shift of +90 degrees of a signal at the first input terminal at a certain frequency of operation, and the second inductor and the second capacitor are configured to cause a phase shift of 90 degrees of a signal at the second input terminal at the frequency of operation.

6. A power combiner for an outphasinq amplifier system, comprising an output terminal; a first input terminal, a first inductor, and a first capacitor, wherein the first input terminal is connected to ground via the first inductor and the first input terminal is connected to the output terminal via the first capacitor; and a second input terminal, a second capacitor, and a second inductor, wherein the second input terminal is connected to ground via the second capacitor and the second input terminal is connected to the output terminal via the second inductor, wherein $C_m=\frac{1}{\left(.Math.\sqrt{R_s.Math.R_1}\right)}\mathrm{and}$ $L_m=\frac{\sqrt{R_s.Math.R_1}}{},$ wherein
=2f.sub.res, wherein f.sub.res is a frequency of operation, R.sub.l denotes the resistance of a load connected to the output terminal, and R.sub.s denotes an optimal load resistance for a power amplifier.

7. The power combiner of claim 6, wherein $L_{\mathrm{comp}}=\frac{R_1}{\sin \left(2{}_{\mathrm{comp}}\right)}\mathrm{and}$ $C_{\mathrm{comp}}=\frac{\sin \left(2{}_{\mathrm{comp}}\right)}{R_1},$ wherein .sub.comp denotes a compensation angle.

8. An amplifier system comprising a power combiner according to claim 1, the amplifier system further comprising a signal component separator for converting an amplitude modulated signal into at least two outphased signals; at least two power amplifiers corresponding to the plurality of outphased signals, each power amplifier of the plurality of power amplifiers being configured to amplify one of the outphased signals, to obtain amplified outphased signals; and wherein the power amplifiers are configured to provide respective ones of the amplified outphased signals to the first input terminal of the power combiner and the second input terminal of the power combiner.

9. A method of a power combiner of an outphasinq amplifier system, comprising providing a first outphased signal to a first input terminal, wherein the first input terminal is connected to ground via a first inductor and the first input terminal is connected to an output terminal via a first capacitor; and providing a second outphased signal to a second input terminal, wherein the second input terminal is connected to ground via a second capacitor and the second input terminal is connected to the output terminal via a second inductor, wherein the second capacitor has a capacitance C.sub.tot substantially equal to a capacitance of a parallel combination of a capacitor having a capacitance C.sub.m equal to the capacitance of the first capacitor and a compensation capacitance C.sub.comp, and the first inductor has an inductance L.sub.tot substantially equal to an inductance of a parallel combination of an inductor having an inductance L.sub.m equal to the inductance of the second inductor and a compensation inductance L.sub.comp.

10. The method of claim 9, wherein the first input terminal is further connected to ground via a first compensation impedance, and the second input terminal is further connected to ground via a second compensation impedance.

11. The method of claim 10, wherein the first compensation impedance comprises a capacitance and the second compensation impedance comprises a inductor, or the first compensation impedance comprises a inductor and the second compensation impedance comprises a capacitance.

12. The method of claim 9, wherein at least one of the first compensation impedance and the second compensation impedance is adjustable.

13. A method of a power combiner of an outphasinq amplifier system, comprising providing a first outphased signal to a first input terminal, wherein the first input terminal is connected to ground via a first inductor and the first input terminal is connected to an output terminal via a first capacitor; and providing a second outphased signal to a second input terminal, wherein the second input terminal is connected to ground via a second capacitor and the second input terminal is connected to the output terminal via a second inductor, wherein the first capacitor and the first inductor can cause a phase shift of +90 degrees of a signal at the first input terminal at a certain frequency of operation, and the second inductor and the second capacitor can cause a phase shift of 90 degrees of a signal at the second input terminal at the frequency of operation.

14. A method of a power combiner of an outphasing amplifier system, comprising providing a first outphased signal to a first input terminal, wherein the first input terminal is connected to ground via a first inductor and the first input terminal is connected to an output terminal via a first capacitor; and providing a second outphased signal to a second input terminal, wherein the second input terminal is connected to ground via a second capacitor and the second input terminal is connected to the output terminal via a second inductor, wherein $C_m=\frac{1}{\left(.Math.\sqrt{R_s.Math.R_1}\right)}\mathrm{and}$ $L_m=\frac{\sqrt{R_s.Math.R_1}}{},$ wherein
=2f.sub.res, wherein f.sub.res is a frequency of operation, R.sub.l denotes the resistance of a load connected to the output terminal, and R.sub.s denotes an optimal load resistance for a power amplifier.

15. The method of claim 14, wherein $L_{\mathrm{comp}}=\frac{R_1}{\sin \left(2{}_{\mathrm{comp}}\right)}\mathrm{and}$ $C_{\mathrm{comp}}=\frac{\sin \left(2{}_{\mathrm{comp}}\right)}{R_1},$ wherein .sub.comp denotes a compensation angle.

16. An amplifier system comprising a power combiner according to claim 5, the amplifier system further comprising a signal component separator for converting an amplitude modulated signal into at least two outphased signals; at least two power amplifiers corresponding to the plurality of outphased signals, each power amplifier of the plurality of power amplifiers being configured to amplify one of the outphased signals, to obtain amplified outphased signals; and wherein the power amplifiers are configured to provide respective ones of the amplified outphased signals to the first input terminal of the power combiner and the second input terminal of the power combiner.

17. An amplifier system comprising a power combiner according to claim 6, the amplifier system further comprising a signal component separator for converting an amplitude modulated signal into at least two outphased signals; at least two power amplifiers corresponding to the plurality of outphased signals, each power amplifier of the plurality of power amplifiers being configured to amplify one of the outphased signals, to obtain amplified outphased signals; and wherein the power amplifiers are configured to provide respective ones of the amplified outphased signals to the first input terminal of the power combiner and the second input terminal of the power combiner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, aspects of the invention will be elucidated by means of examples, with reference to the drawings. The drawings are diagrammatic and may not be drawn to scale. Throughout the drawings, similar items may be denoted by the same reference numerals.

(2) FIG. 1 shows a diagram of an outphasing amplifier system.

(3) FIG. 2A shows a diagram of an implementation of a power combiner.

(4) FIGS. 2B and 2C show diagrams of impedances related to FIG. 2A.

(5) FIG. 3A shows a power combiner using a transformer.

(6) FIG. 3B shows a power combiner using a quarter wave line.

(7) FIG. 4A shows a diagram of a power combiner.

(8) FIG. 4B shows a diagram of a power combiner with compensation impedances.

(9) FIG. 5 shows a diagram of a power combiner.

(10) FIG. 6 shows a diagram of a power combiner.

(11) FIGS. 7A and 7B show diagrams of efficiency of a particular power combiner.

(12) FIGS. 8A and 8B show diagrams of efficiency of a particular power combiner.

(13) FIGS. 9A and 9B show diagrams of efficiency of a particular power combiner.

DESCRIPTION

(14) Certain exemplary embodiments will be described in greater detail, with reference to the accompanying drawings.

(15) The matters disclosed in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. Accordingly, it is apparent that the exemplary embodiments can be carried out without those specifically defined matters. also, well-known operations or structures are not described in detail, since they would obscure the description with unnecessary detail.

(16) FIG. 4A shows a lumped outphasing power combiner based on an LC balun. The power combiner comprises a first input terminal 411, a second input terminal 421, and an output terminal 405. The input terminals 411, 421 may be connected to the output of respective power amplifiers 410, 420 of the outphasing amplifier system. The output terminal 405 may be connected to any load 406. For example, the outphasing power combiner 400 may be a novel implementation of the power combiner 104 of FIG. 1.

(17) The power combiner 400 comprises a first inductor 413, and a first capacitor 414. The first input terminal 411 is connected to ground via the first inductor 413 and the first input terminal 411 is connected to the output terminal 405 via the first capacitor 414. That is, one terminal of the first inductor 413 is connected to the first input terminal 411 and another terminal of the first inductor 413 is connected to a ground. A first terminal of the first capacitor is connected to the first input terminal 411, and another terminal of the first capacitor is connected to the output terminal 405. The compensation capacitor 412 is an optional component, which may be omitted in certain implementations.

(18) The power combiner 400 further comprises a second capacitor 423, and a second inductor 424. The second input terminal 421 is connected to ground via the second capacitor 423 and the second input terminal 421 is connected to the output terminal 405 via the second inductor 424. That is, one terminal of the second capacitor 423 is connected to the second input terminal 421, and another terminal of the second capacitor 423 is connected to a ground. One terminal of the second inductor 424 is connected to the second input terminal 421, and another terminal of the second inductor 424 is connected to the output terminal 405. The compensation inductor 422 is an optional component, which may be omitted in certain implementations.

(19) By means of the compensation shunt components 413 and 423, the efficiency can be restored to maximum for a certain outphasing angle. As an implementation example, the signal component separator 103 may generate constant envelope signals. The power amplifiers 410, 420 may be implemented as nonlinear switched mode power amplifiers, which may be highly efficient.

(20) The second capacitor 423 and the second inductor 424 may be referred to as a low-pass LC section. This low-pass LC section may generate a phase shift of 90 degrees at its resonance frequency. The first inductor 413 and the first capacitor 414 may be referred to as a high-pass LC section. This high-pass LC section may generate a phase shift of +90 degrees at its resonance frequency. Both sections may have the same resonance frequency. If the second input terminal 421 is provided with a signal having a 180 degrees phase, the phase shift at the output terminal 405 will be +90 degrees (i.e., 180-90 degrees phase shift). If the first input terminal 411 is provided with a signal having a 0 degrees phase, the phase shift at the output terminal 405 will also become +90 degrees (i.e., 0+90 degrees phase shift). To achieve this, the first capacitor 414 may have a same capacitance as the second capacitor 423 and the first inductor 413 may have a same inductance as the second inductor 424.

(21) In other words, at the output terminal 405 both signals may have the same phase and sum up. The 0 and 180 degrees signals provided at the first and second input terminals, respectively, may be regarded as a differential signal (balanced) which gets converted to a single ended (unbalanced) signal by the combiner 400.

(22) In certain embodiments, the capacitance C.sub.m of the first capacitor 414 and the second capacitor 423 may be defined as:

(23) $C_m=\frac{1}{\left(.Math.\sqrt{R_s.Math.R_1}\right)}.$
Moreover, the inductance L.sub.m of the first inductance 413 and the second inductance 424 may be defined as:

(24) $L_m=\frac{\sqrt{R_s.Math.R_1}}{}.$
In the above two equations,
=2f.sub.res,

(25) wherein f.sub.res is the resonance frequency of the power combiner, more particularly of the LC combination 413, 424, 414, 423. This resonance frequency f.sub.res may be chosen equal to the operating frequency of the outphasing amplifier system containing the power combiner. Therefore, the resonance frequency may alternatively be referred to as frequency of operation.

(26) Moreover, R.sub.l denotes the resistance of the load 406, for example an antenna load. R.sub.s denotes an optimal load resistance for the power amplifiers. The optimal load resistance may be determined, for example, by simulations of the amplifiers (PA's). It is the resistance for which the amplifiers will deliver maximum output power.

(27) FIG. 4B illustrates that the power combiner may further (optionally) comprise a first compensation impedance and a second compensation impedance. These compensation impedances may be compensating for the impedances Z.sub.1 and Z.sub.2, described above with reference to FIG. 2A to 2C. The kind of compensation impedance (e.g. inductor or capacitor) may depend on the way in which the signals are separated by the signal component separator 103. In case the compensation impedances are present, the first input terminal 411 may be further connected to ground via the first compensation impedance, and the second input terminal 421 may be further connected to ground via the second compensation impedance.

(28) In the implementation shown in FIG. 4B, the first compensation impedance comprises a capacitance 412 and the second compensation impedance comprises a inductor 422.

(29) FIG. 5 shows an example of a power combiner 500 with a different implementation of the compensation impedances. In FIG. 5, the first compensation impedance comprises a inductor 512, and the second compensation impedance comprises a capacitance 522. Otherwise, the power combiner of FIG. 5 is identical to the power combiner of FIG. 4B. The different configurations of FIG. 4B and FIG. 5 may make the power combiner more suitable for differently separated signal components.

(30) The compensation inductor and capacitor values L.sub.comp and C.sub.comp, as shown in FIG. 5 and FIG. 6, can be calculated, for example, by making the reactive parts L.sub.comp and C.sub.comp equal but opposite sign with respect to the virtual load reactances Z.sub.1 and Z.sub.2. For example, for a compensation angle .sub.comp:

(31) 0$L_{\mathrm{comp}}=\frac{R_1}{\sin \left(2{}_{\mathrm{comp}}\right)},C_{\mathrm{comp}}=\frac{\sin \left(2{}_{\mathrm{comp}}\right)}{R_1}.$

(32) In certain implementations, as tentatively illustrated in FIG. 5, the compensation inductor 512 and the first inductor 413 may be combined as a single inductor 531 that replaces the compensation inductor 512 and the first inductor 413. Similarly, the compensation capacitor 522 and the second capacitor 423 may be combined as a single capacitor 532 that replaces the compensation capacitor 522 and the second capacitor 423. This configuration may further reduce the chip surface needed to implement the power combiner.

(33) The inductance L.sub.tot of the combined inductor 531 may be equal to the inductance of the parallel combination of the compensation inductor and balun inductor, as follows:

(34) $L_{\mathrm{tot}}=\frac{L_m{L}_{\mathrm{comp}}}{L_m+L_{\mathrm{comp}}}.$

(35) The capacitance C.sub.tot of the combined capacitor 532 may be equal to the capacitance of the parallel combination of the compensation and balun capacitor, as follows:
C.sub.tot=C.sub.m+C.sub.comp.

(36) FIG. 6 shows a diagram of another example of a power combiner 600, in which the compensation impedances 612, 622 have been made variable. For example, the compensation impedances may be made switchable (at discrete levels) or tunable (at continuous levels). For example, the inductance of the compensation inductor 612 may be made variable, and/or the capacity of the compensation capacitor 622 may be made variable. As shown in FIG. 6, the variable compensation impedances may be implemented as separate component next to the first inductor 413 and the second capacitor 423. Alternatively, as also shown in FIG. 6, the variable inductor 612 and the first inductor 413 may be combined into a single variable inductor 631. Likewise, the variable capacitor 622 and the second capacitor 423 may be combined into a single variable capacitor 632.

(37) Although not illustrated, in the configuration shown in FIG. 4B it is also possible to make the compensation capacitor 412 and the compensation inductor 422 variable.

(38) FIG. 7A and FIG. 7B show examples of the efficiency of the power combiner 400 of FIG. 4A, according to a simulation with ideal components. Plotted in FIG. 7A is combiner efficiency (combiner_eff) versus outphasing angle (phi) in degrees, and plotted in FIG. 7B is combiner efficiency (combiner_eff) versus normalized output power (normalized_power) in decibel (dB). Herein, the normalized output power is the output power normalized with respect to the maximum output power.

(39) As a measure for the power amplifier and combined efficiency, the efficiency may be defined as real power delivered to the load divided by the magnitude of the complex power drawn from the ideal voltage sources.

(40) As expected above, the maximum output power may be achieved in certain embodiments for an outphasing angle of 90 degrees, so 180 degrees of phase difference between the two power amplifiers. Efficiency and output power may drop as the outphasing angle is decreased, due to an increase of the virtual reactive component value (Z.sub.1 and Z.sub.2), as explained above with reference to FIG. 2.

(41) FIG. 8A and FIG. 8B show examples of the efficiency of the power combiner 401 of FIG. 4B, according to simulation results based on ideal lumped components and presence of compensation impedances for a compensation angle .sub.comp of 15 degrees. The combiner efficiency has, in this case, two peaks, at 15 degrees and at 75 degrees. The efficiency plotted versus normalized power shows that two power levels can be generated with equal maximum efficiency: one power level at a normalized power of 0 dB and one at a 6 dB power level.

(42) FIG. 9A and FIG. 9B show examples of the efficiency of the power combiner 500 shown in FIG. 5. Because the compensation capacitor and the compensation impedance of power combiner 500 have swapped placed compared to the power combiner 401, the compensation realized by power combiner 500 may occur for negative outphasing angles. FIG. 9A and FIG. 9B show plots of efficiency according to simulation results based on ideal lumped components and presence of compensation impedances for a compensation angle .sub.comp of 15 degrees. Again, maximum efficiency may be realized at a normalized power of 0 dB and normalized power at 6 dB.

(43) As disclosed hereinabove with reference to FIG. 6, the compensation capacitor and inductor can be made switchable (discrete levels) or tunable (continuous levels) so that over a wide range of powers a constant efficiency can be achieved.

(44) The examples and embodiments described herein serve to illustrate rather than limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the spirit and scope of the present disclosure, as defined by the appended claims and their equivalents. Reference signs placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single hardware or software item combining the features of the items described.