LOW-LOSS QUASI-CIRCULATOR

Abstract

There is provided a quasi-circulator. The quasi-circulator includes: a first coupler having an input end connected to a transmission end; a first amplifier having an input end connected to an output end of the first coupler; a second amplifier having an input end connected to the output end of the first coupler; a second coupler having one end connected to an output end of the first amplifier and an output end of the second amplifier, and the other end connected to an antenna; and a third coupler having one end connected to the output end of the first amplifier and the output end of the second amplifier, and the other end connected to a reception end. Accordingly, a loss occurring at the quasi-circulator is minimized, and eventually, efficiency of an RF FEM employed in an ultrahigh frequency radar system is enhanced.

Claims

1. A quasi-circulator comprising: a first coupler having an input end connected to a transmission end; a first amplifier having an input end connected to an output end of the first coupler; a second amplifier having an input end connected to the output end of the first coupler; a second coupler having one end connected to an output end of the first amplifier and an output end of the second amplifier, and the other end connected to an antenna; and a third coupler having one end connected to the output end of the first amplifier and the output end of the second amplifier, and the other end connected to a reception end.

2. The quasi-circulator of claim 1, wherein the first coupler is configured to distribute a transmission signal inputted through the input end into two signals having a phase difference of 90 degrees, and to output the signals, wherein the first amplifier is configured to amplify one of the signals outputted from the output end of the first coupler, wherein the second amplifier is configured to amplify the other one of the signals outputted from the output end of the first coupler, and wherein the second coupler is configured to convert the phase difference between the output signal of the first amplifier and the output signal of the second amplifier into 0 degree, and to transmit the signals to the antenna.

3. The quasi-circulator of claim 1, wherein the signals outputted from the first amplifier and the second amplifier have power equally distributed and transmitted to the second coupler and the third coupler.

4. The quasi-circulator of claim 3, wherein an impedance when the second coupler and the third coupler are seen from the output end of the first amplifier is a sum of an impedance of the second coupler and an impedance of the third coupler, wherein an impedance when the second coupler and the third coupler are seen from the output end of the second amplifier is the sum of the impedance of the second coupler and the impedance of the third coupler, and wherein the impedance of the second coupler is equal to the impedance of the third coupler.

5. The quasi-circulator of claim 3, wherein the third coupler is configured to offset the phase difference between the output signal of the first amplifier and the output signal of the second amplifier by converting the phase difference into 180 degrees.

6. The quasi-circulator of claim 1, wherein the second coupler is configured to distribute a reception signal inputted through the antenna into two signals having a phase difference of 90 degrees, and to output the signals, wherein the third coupler is configured to convert the phase difference between output signals of the second coupler into 0 degree and to transmit the signals to the reception end.

7. The quasi-circulator of claim 6, wherein the first amplifier and the second amplifier are configured to block the output signals of the second coupler.

8. A communication method comprising the steps of: distributing, by a first coupler, a transmission signal inputted from a transmission end into two signals, and output the signals; amplifying, by a first amplifier, one of the distributed transmission signals; amplifying, by a second amplifier, the other one of the distributed transmission signals; transmitting, by a second coupler, the amplified transmission signals to an antenna; and offsetting, by a third coupler, the amplified transmission signals at a reception end.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0022] FIG. 1 is a view illustrating an RF FEM structure of a communication system;

[0023] FIG. 2 is an RF structure in which transmission and reception antennas are separated;

[0024] FIG. 3 is a view illustrating an RF FEM structure using a circulator;

[0025] FIG. 4 is a view illustrating a circulator design using a coupler;

[0026] FIG. 5 is a view illustrating a quasi-circulator structure; and

[0027] FIG. 6 is a view illustrating a structure of a low-loss quasi-circulator according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0028] Hereinafter, the present disclosure will be described in more detail with reference to the accompanying drawings.

[0029] Embodiments of the present disclosure suggest a low-loss quasi-circulator. In embodiments of the present disclosure, a quasi-circulator of a low loss is implemented by using two power amplifiers and three hybrid couplers, which is different from a related-art structure in which a loss is great at a transmission end a reception end.

[0030] FIG. 6 is a view illustrating a structure of a low-loss quasi-circulator according to an embodiment of the present disclosure. As shown in the drawing, the quasi-circulator according to an embodiment may include a hybrid coupler-1 C1, a power amplifier-1 PA1, a power amplifier-2 PA2, a hybrid coupler-2 C2, and a hybrid coupler-3 C3.

[0031] The hybrid coupler-1 C1 has an input end connected to a transmission end Tx and an output end connected to the power amplifiers PA1, PA2. The hybrid coupler-1 C1 distributes a transmission signal inputted from the transmission end Tx to the power amplifiers PA1, PA2.

[0032] The power amplifiers PA1, PA2 have input ends connected to the output end of the hybrid coupler-1 C1, and have output ends connected to the hybrid coupler-2 C2 and the hybrid coupler-3 C3.

[0033] The hybrid coupler-2 C2 has one end connected to the output ends of the power amplifiers AP1, PA2, and the other end connected to an antenna. The hybrid coupler-2 C2 transmits the transmission signal outputted from the output ends of the power amplifiers PA1, PA2 to the antenna, and transmits a reception signal received at the antenna to the hybrid coupler-3 C3.

[0034] The hybrid coupler-3 C3 has one end connected to the output ends of the power amplifiers PA1, PA2, and the other end connected to a reception end Rx. The hybrid coupler-3 C3 transmits the reception signal of the antenna transmitted through the hybrid coupler-2 C2 to the reception end Rx.

[0035] On the other hand, an impedance 2*Zo when the hybrid coupler-2 C2 and the hybrid coupler-3 C3 are seen from the output end of the power amplifier-1 PA1 is a sum of an impedance Zo of the hybrid coupler-2 C2 and an impedance Zo of the hybrid coupler-3 C3.

[0036] Likewise, an impedance 2*Zo when the hybrid coupler-2 C2 and the hybrid coupler-3 C3 are seen from the output end of the power amplifier-2 PA2 is the sum of the impedance Zo of the hybrid coupler-2 C2 and the impedance Zo of the hybrid coupler-3 C3.

[0037] In addition, the hybrid coupler-1 C1, the hybrid coupler-2 C2, and the hybrid coupler-3 C3 are implemented equally, such that the impedance Zo is the same.

[0038] Power amplifiers do not have to be connected to the input end of the hybrid coupler-1 C1. This is because the power amplifiers PA1, PA2 at the output end perform the roles of power amplifiers at the input end. Accordingly, the power amplifiers PA1, PA2 are added to the output end of the hybrid coupler-1 C1, but the power amplifiers are omitted from the input end, and therefore, the whole area of the communication system is not regarded as increasing.

[0039] A transmission mode operation of the quasi-circulator according to an embodiment will be described in detail.

[0040] When a transmission signal is inputted from the transmission end Tx through the input end, the hybrid coupler-1 C1 distributes the inputted transmission signal into two signals having a phase difference of 90 degrees (a 0-degree signal having a phase of 0 degree and a 90-degree signal having a phase of 90 degrees), and outputs the signals.

[0041] Then, the power amplifier-1 PA1 amplifies and outputs the 0-degree signal, and the power amplifier-2 PA2 amplifies and outputs the 90-degree signal. The transmission signals outputted from the power amplifier-1 PA1 and the power amplifier-2 PA2 have power equally distributed and transmitted to the hybrid coupler-2 C2 and the hybrid coupler-3 C3. This is because output matching of the power amplifier-1 PA1 and the power amplifier-2 PA2 is set to 2*Zo.

[0042] The 0-degree signal amplified at the power amplifier-1 PA1 may be converted into a 90-degree signal at the hybrid coupler-2 C2, and may be outputted to the antenna, and the 90-degree signal amplified at the power amplifier-2 PA2 may be outputted from the hybrid coupler-2 C2 to the antenna as the 90-degree signal.

[0043] As described above, the hybrid coupler-2 C2 converts the phase difference between the output signal of the power amplifier-1 PA1 and the output signal of the power amplifier-2 PA2 into 0 degree and transmits the signals to the antenna, such that the two signals having the same phase are combined with each other and are transmitted to the antenna.

[0044] Since the power amplifier-1 PA1 and the power amplifier-2 PA2 have the same output power as an existing power amplifier, and respective halves of the output power are combined at the hybrid coupler-2 C2, DC power consumption is high in comparison to that of an existing structure, but output power reflects only the loss of C2. Therefore, the output power may be deemed to have a low loss.

[0045] Meanwhile, the 0-degree signal amplified at the power amplifier-1 PA1 may be outputted from the hybrid coupler-3 C3 to the reception end Rx as the 0-degree signal, and the 90-degree signal amplified at the power amplifier-2 PA2 may be converted into a 180-degree signal at the hybrid coupler-3 C3 and may be outputted to the reception end Rx.

[0046] As described above, since the hybrid coupler-3 C3 converts the phase difference between the output signal of the power amplifier-1 PA1 and the output signal of the power amplifier-2 PA2 into 180 degrees, the two signals are offset and are not transmitted to the reception end Rx. That is, the reception end Rx is isolated from the transmission end Tx and power transmitted to the other output end of the hybrid coupler-3 C3 is absorbed by a resistance.

[0047] As described above, the quasi-circulator according to an embodiment guarantees a path from the transmission end Tx to the antenna, whereas it is identified that a path from the transmission end Tx to the reception end Rx is isolated. In addition, since a loss occurs only at the hybrid coupler-2 C2 on the path from the transmission end Tx to the antenna, the quasi-circulator of the low-loss may be implemented.

[0048] Hereinafter, a reception mode operation of the quasi-circulator according to an embodiment will be described in detail.

[0049] The hybrid coupler-2 C2 distributes a reception signal inputted through the antenna into two signals having a phase difference of 90 degrees (a signal having a phase of 90 degrees and a signal having a phase of 0 degree), and outputs the signals.

[0050] The 90-degree signal outputted from the hybrid coupler-2 C2 is outputted to the reception end Rx at the hybrid coupler-3 C3 as the 90-degree signal, and the 0-degree signal outputted from the hybrid coupler-2 C2 is converted into a 90-degree signal at the hybrid coupler-3 C3 and is outputted to the reception end Rx.

[0051] That is, the hybrid coupler-3 C3 converts the phase difference of the output signals of the hybrid coupler-2 C2 into 0 degree, and transmits the signals to the reception end Rx, such that the two signals are combined with each other and are inputted to the reception end Rx.

[0052] The signals outputted from the hybrid coupler-2 C2 are blocked at the power amplifiers PA1, PA2 and a leakage of signals does not occur due to reverse isolation, and the signals do not flow into the hybrid coupler-1 C1 and are not inputted to the transmission end Tx.

[0053] As described above, since only two insertion losses of the hybrid coupler-1 C1 and the hybrid coupler-2 C2 occur on the path from the antenna to the reception end Rx, there is an effect that the loss in this path is noticeably reduced.

[0054] In a related-art structure, a loss of 3.5 dB occurs in Tx-to-Antenna and a loss of 3.5 dB occurs in Antenna-to-Rx due to coupler distribution of 3 dB+ and a coupler insertion loss of 0.5 dB. However, in the quasi-circulator according to an embodiment, a loss in Tx-to-Antenna is merely 0.5 dB and a loss in Antenna-to-Rx is merely 1 dB.

[0055] Up to now, the low-loss quasi circulator has been described in detail with reference to preferred embodiments. Embodiments described above suggests a structure of a circulator which minimizes a loss in order to enhance efficiency of an RF FEM of an ultrahigh frequency radar system.

[0056] The quasi-circulator according to an embodiment is applicable to a communication system which uses a full duplex in which a transmission frequency and a reception frequency are the same, in addition to the radar system.

[0057] In addition, while preferred embodiments of the present disclosure have been illustrated and described, the present disclosure is not limited to the above-described specific embodiments. Various changes can be made by a person skilled in the art without departing from the scope of the present disclosure claimed in claims, and also, changed embodiments should not be understood as being separate from the technical idea or prospect of the present disclosure.