Bidirectional amplifier based on LMBA structure and three coupling transformers

Abstract

The invention belongs to the technical field of wireless communication, relates to an amplifier at a radio frequency front end in a transceiving system, and particularly provides a bidirectional amplifier based on an LMBA structure and a three-coupling transformer, which is used for improving the PA efficiency of the bidirectional amplifier and reducing the LNA noise coefficient at the same time. According to the bidirectional amplifier, the three coupling transformers are adopted, the switches are replaced through impedance characteristic changes of the transistors, compared with a bidirectional amplifier structure with the switches, the bidirectional amplifier has low insertion loss in the radio frequency field, the PA efficiency of the bidirectional amplifier is improved, and the LNA noise coefficient is reduced; meanwhile, the PA adopts an LMBA structure, bidirectional amplification of signals is realized by utilizing a BA path, and compared with a conventional bidirectional amplifier, the bidirectional amplifier has the characteristic of high efficiency in a power rollback interval.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and relates to an amplifier in a radio frequency front end of a transceiver system. Specifically, a bidirectional amplifier based on an LMBA structure and a triple-coupled transformer is provided. Background Art

[0002] With the rapid development of modern communication technologies, the radio frequency front end, as the core part of a transceiver system, directly determines the quality of the entire transceiver system. And the amplifier, as the core part of the radio frequency front end, naturally faces higher index requirements. For a radio frequency amplifier, it is divided into a power amplifier (PA) and a low noise amplifier (LNA) according to the transmitting function or receiving function; as the core of a transmitter, the energy consumption of the PA can reach one-third of the entire system; as the first active device of a receiver, the LNA largely determines the noise figure of the system. Therefore, how to improve the efficiency of the PA and reduce the noise of the LNA has great research value.

[0003] A separate transceiver amplifier circuit usually occupies a large area, especially in a system such as a phased array that needs to consider both receiving and transmitting functions at the same time. Therefore, a bidirectional amplifier integrating switches and transmitting and receiving amplifiers has gradually become the research focus; the bidirectional amplifier can share the up and down conversion circuits for the transceiver link, thereby obtaining better integration, reducing the system area and lowering the cost of the radio frequency front end. A basic bidirectional amplifier (Bi-Directional Amplifier, BDA) as Figure 1 shown, switches between the power amplifier and the low noise amplifier through a simple switch. When the single-pole double-throw switch is placed on the transmitting path, the amplifier operates in the PA mode; when the single-pole double-throw switch is placed on the receiving path, the amplifier operates in the LNA mode; however, when amplifying a high peak-to-average ratio signal, the low power output efficiency of the basic bidirectional amplifier (BDA) is low and it is difficult to meet the application requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a bidirectional amplifier based on an LMBA structure and a triple-coupled transformer to improve the PA efficiency of the bidirectional amplifier while reducing the LNA noise figure; the present invention uses a triple-coupled transformer and realizes the replacement of the switch by using the impedance characteristic change of a transistor. Compared with the bidirectional amplifier structure with a switch, it has lower insertion loss in the radio frequency field, realizes the improvement of the PA efficiency of the bidirectional amplifier and the reduction of the LNA noise figure; at the same time, the PA adopts an LMBA structure and realizes the bidirectional amplification of the signal by using the BA path. Compared with the conventional bidirectional amplifier, it has the characteristic of high efficiency in the power back-off interval.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A bidirectional amplifier based on the LMBA structure and a triple-coupled transformer, comprising: a power divider, quadrature couplers Coupler1 and Coupler2, a CA path, a BA1 path, a BA2 path, an LNA1 path, an LNA2 path, and triple-coupled transformers Transformer1 to Transformer4; characterized in that:

[0007] The BA1 path and the LNA1 path form a first bidirectional balanced branch, and the BA2 path and the LNA2 path form a second bidirectional balanced branch. The first bidirectional balanced branch and the second bidirectional balanced branch adopt the same circuit (the circuit structure and parameters are exactly the same);

[0008] The input end of the power divider serves as the input end in the PA mode and the output end in the LNA mode. One output of the power divider is connected to the CA path, and the output of the CA path is connected to the isolation end of the quadrature coupler Coupler2. The other output of the power divider is connected to the input end of the quadrature coupler Coupler1. The quadrature ends (through end and coupled end) of the quadrature coupler Coupler1 are respectively connected to the first bidirectional balanced branch and the second bidirectional balanced branch through the triple-coupled transformers Transformer1 and Transformer2. The first bidirectional balanced branch and the second bidirectional balanced branch are then respectively connected to the quadrature ends (through end and coupled end) of the quadrature coupler Coupler2 through the triple-coupled transformers Transformer3 and Transformer4. The isolation end of the quadrature coupler Coupler1 is connected to an isolation resistor to ground, and the input end of the quadrature coupler Coupler2 is connected to a transceiver antenna.

[0009] Further, the CA path includes: a driver-stage amplifier DA and a power-stage amplifier CA. The driver-stage amplifier DA and the power-stage amplifier CA are connected in series. The input end of the driver-stage amplifier DA is connected to the output end of the power divider through a matching transformer, and the output end of the power-stage amplifier CA is connected to the isolation end of the quadrature coupler Coupler2 through a matching transformer.

[0010] Further, in the first bidirectional balanced branch, the BA1 path includes: a driver amplifier DA and a power amplifier BA1, and the LNA1 path includes: a driver amplifier DA and a low-noise amplifier LNA1; the driver amplifier DA and the power amplifier BA1 in the BA1 path are connected in series. The input end of the driver amplifier DA in the BA1 path is connected to the tertiary coil of the triple-coupling transformer Transformer1, and the output end of the power amplifier BA1 in the BA1 path is connected to the tertiary coil of the triple-coupling transformer Transformer3; the low-noise amplifier LNA1 and the driver amplifier DA in the LNA1 path are connected in series. The input end of the low-noise amplifier LNA1 in the LNA1 path is connected to the primary coil of the triple-coupling transformer Transformer3, and the output end of the driver amplifier DA in the LNA1 path is connected to the primary coil of the triple-coupling transformer Transformer1; the secondary coil of the triple-coupling transformer Transformer1 is connected to the through end of the quadrature coupler Coupler1, and the secondary coil of the triple-coupling transformer Transformer3 is connected to the coupled end of the quadrature coupler Coupler2.

[0011] Further, in the second bidirectional balanced branch, the BA2 path includes: a driver amplifier DA and a power amplifier BA2, and the LNA2 path includes: a driver amplifier DA and a low-noise amplifier LNA2; the driver amplifier DA and the power amplifier BA2 in the BA2 path are connected in series. The input end of the driver amplifier DA in the BA2 path is connected to the tertiary coil of the triple-coupling transformer Transformer2, and the output end of the power amplifier BA2 in the BA2 path is connected to the tertiary coil of the triple-coupling transformer Transformer4; the low-noise amplifier LNA2 and the driver amplifier DA in the LNA2 path are connected in series. The input end of the low-noise amplifier LNA2 in the LNA2 path is connected to the primary coil of the triple-coupling transformer Transformer4, and the output end of the driver amplifier DA in the LNA2 path is connected to the primary coil of the triple-coupling transformer Transformer2; the secondary coil of the triple-coupling transformer Transformer2 is connected to the coupled end of the quadrature coupler Coupler1, and the secondary coil of the triple-coupling transformer Transformer4 is connected to the through end of the quadrature coupler Coupler2.

[0012] Further, when the bidirectional amplifier operates in the PA mode, both the LNA1 path and the LNA2 path are biased to zero, the BA1 path and the BA2 path are biased in the Class-AB mode, and the CA path is biased in the Class-C mode.

[0013] Further, when the bidirectional amplifier operates in the LNA mode, the CA path, the BA1 path, and the BA2 path are all biased to zero, and the LNA1 path and the LNA2 path are biased in the Class-A mode.

[0014] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0015] The present invention provides a bidirectional amplifier based on an LMBA structure and a three-coupled transformer, which realizes bidirectional amplification of signals through the LMBA architecture and the three-coupled amplifier. First, by using the LMBA structure, bidirectional amplification of signals is achieved on the LMBA architecture, resulting in a significant improvement in PA efficiency compared to traditional bidirectional amplifiers. Second, by using the three-coupled transformer structure and the impedance change of transistors, the on-off control of the circuit is realized. Without the restriction of switches compared to traditional amplifiers, the characteristics such as efficiency and noise figure of the bidirectional amplifier in the radio frequency field have been significantly improved.

[0016] In summary, the present invention adopts a current branch control structure without switches, eliminates the performance degradation caused by switches in traditional bidirectional amplifiers, takes into account the high efficiency of the PA and the low noise figure of the LNA, has high efficiency in the back-off range in the PA mode, expands the application scenarios of bidirectional amplifiers, and makes it possible to use bidirectional amplifiers in high peak-to-average ratio signal transmission scenarios. Brief Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of a basic bidirectional amplifier (BDA).

[0018] Figure 2 It is a schematic structural diagram of a load modulation balanced amplifier (LMBA).

[0019] Figure 3 It is a model diagram of a coupler in a load modulation balanced amplifier.

[0020] Figure 4 It is a model diagram of a three-coupled transformer.

[0021] Figure 5 It is a π-shaped model diagram of an integrated inductor.

[0022] Figure 6 It is a simplified model diagram of an integrated inductor.

[0023] Figure 7 It is a simplified model diagram of a three-coupled transformer.

[0024] Figure 8 It is a schematic structural diagram of the bidirectional amplifier based on the LMBA structure and the three-coupled transformer provided by the present invention.

[0025] Figure 9 It is a schematic working principle diagram of the PA mode of the bidirectional amplifier based on the LMBA structure and the three-coupled transformer provided by the present invention.

[0026] Figure 10Current curve diagrams of the BA path and the CA path in the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0027] Figure 11 Impedance curve diagrams of the BA path and the CA path in the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0028] Figure 12 PA mode gain curve diagram of the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0029] Figure 13 PA mode PAE curve diagram of the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0030] Figure 14 Working principle diagram of the LNA mode of the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0031] Figure 15 LNA mode gain curve diagram of the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention.

[0032] Figure 16 LNA mode PAE curve diagram of the bidirectional amplifier based on the LMBA structure and the triple-coupled transformer provided by the present invention. Detailed implementation manners

[0033] To make the objectives, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] The present invention proposes a bidirectional amplifier based on the LMBA structure and the triple-coupled transformer. As a bidirectional amplifier, it can work in the PA mode and the LNA mode respectively.

[0035] In terms of working principle:

[0036] 1. Load Modulated Balanced Amplifier (LMBA);

[0037] The Load Modulated Balanced Amplifier (LMBA) is as Figure 2 shown. The LMBA mainly consists of a balanced amplifier (BA), a carrier amplifier (CA), and a quadrature coupler; the quadrature coupler plays a key role in the LMBA structure. The coupler model is as Figure 3 shown. Apply an excitation to port 1 of the coupler. Assuming that the remaining ports are all connected to the load impedance Z0, the voltages of the remaining ports after odd-even mode analysis are:

[0038]

[0039] Among them, Z 0e and Z 0o are the characteristic impedances of the even mode and the odd mode respectively, and θ is the electrical length of the coupler;

[0040] The impedance matrix of the coupler is:

[0041]

[0042] Among them,

[0043] When the length of the coupler is λ / 4, θ = 90°, the voltage amplitudes at the coupled end and the through end are equal, and the phase difference is 90°; then the impedance matrix of the quadrature coupler is:

[0044]

[0045] Let the current in the BA path be I ba1 = -i ba1 and I ba2 = -j×i ba2 , if the phase shift of the current I ca in the CA path relative to I ba1 is α, that is, I ca = -i ca e jα ; substituting it into the impedance matrix of the quadrature coupler, we can get:

[0046]

[0047] It can be seen that the impedance seen from the CA path is a fixed value and does not change with the current; the impedance seen from the BA path changes with the ratio of the current magnitudes in the CA path and the BA path. If the phase shift of I ca relative to I ba1 is α = 0 / π, then the impedance seen from the BA path is purely real; that is, the load-modulated balanced amplifier (LMBA) can achieve modulation of the impedance of the BA path by controlling the current magnitudes and phases in the CA path and the BA path.

[0048] 2. Three-coupled transformer;

[0049] Inductive coupling plays a key role in millimeter-wave circuits and systems. Inductive coupling focuses on the coupling coefficient and the inductance value of the coil. The coupling process is the change of self-inductance and mutual inductance currents between inductors;

[0050] Such as Figure 4The figure shows a model of a three-coupled transformer. LP is the primary coil, LS is the secondary coil, LT is the tertiary coil, and k1, k2, and k3 are the coupling coefficients between LP and LS, LS and LT, and LP and LT, respectively;

[0051] As Figure 5 shown, a relatively accurate π-shaped model of an integrated inductor is given. L is the inductance of the coil, Rs is the loss of the coil, Cx and Cp are the parasitic capacitances of the coil, and Csub and Rsub are the parasitic capacitance and parasitic inductance of the substrate; since the operating frequency is less than the self-resonant frequency of the coil and the substrate parasitic parameters have little influence on the coil model, the circuit can be simplified. The simplified integrated inductor model is as Figure 6 shown; on this basis, the model of the three-coupled transformer is simplified to be as Figure 7 shown. L1 to L3 are the inductances of the primary, secondary, and tertiary coils in sequence, and Rs1 to Rs3 are the losses of the primary, secondary, and tertiary coils in sequence; the primary coil is connected to the external input V1, and the secondary coil and the tertiary coil are connected to transistors; taking the secondary coil as an example, when the transistor is turned on, the equivalent resistance value is small, while when the transistor is turned off, the equivalent resistance is large, approximately a series connection of an equivalent resistance r2 and an equivalent switch sw2; similarly, for the tertiary coil, the transistor connected to it is approximately a series connection of an equivalent resistance r3 and an equivalent switch sw3;

[0052] Assume that the losses of the primary, secondary, and tertiary coils are the same, Rs1 = Rs2 = Rs3 = Rs. Then, the relationships between the voltage, current, and impedance of the three-coupled transformer are as follows:

[0053]

[0054] Among them, V1, V2, and V3 represent the port voltages of the primary, secondary, and tertiary coils, and I1, I2, and I3 represent the port currents of the primary, secondary, and tertiary coils; ω represents 2πf, f is the operating frequency, M12 represents the mutual inductance between the primary coil and the secondary coil, M23 represents the mutual inductance between the secondary coil and the tertiary coil, and M13 represents the mutual inductance between the primary coil and the tertiary coil;

[0055] If sw3 is disconnected, then I3 is 0 and V3 is 0:

[0056]

[0057] 0 = jωM13×I1 + jωM23×I2

[0058] Since I1 and I2 are not 0, it is not difficult to obtain that M13 and M23 are also 0. Since so k2 and k3 are 0, and the three-coupled transformer degenerates into a two-coupled transformer, which is expressed as:

[0059]

[0060] On this basis, the present invention combines a load modulation balanced amplifier (LMBA) with a triple-coupled transformer to propose a bidirectional amplifier, as Figure 8 shown, specifically including: a power divider, quadrature couplers Coupler1 and Coupler2, a CA path, a BA1 path, a BA2 path, an LNA1 path, an LNA2 path, and triple-coupled transformers Transformer1 to Transformer4; the BA1 path and the LNA1 path form a first bidirectional balanced branch, and the BA2 path and the LNA2 path form a second bidirectional balanced branch. The first bidirectional balanced branch and the second bidirectional balanced branch adopt the same circuit (the circuit structure and parameters are exactly the same); wherein: the input end of the power divider serves as the input end of the PA mode and the output end of the LNA mode. One output of the power divider is connected to the CA path, and the output of the CA path is connected to the isolation end of the quadrature coupler Coupler2; the other output of the power divider is connected to the input end of the quadrature coupler Coupler1. The quadrature ends (through end and coupled end) of the quadrature coupler Coupler1 are respectively connected to the first bidirectional balanced branch and the second bidirectional balanced branch through the triple-coupled transformers Transformer1 and Transformer2. The first bidirectional balanced branch and the second bidirectional balanced branch are then respectively connected to the quadrature ends (through end and coupled end) of the quadrature coupler Coupler2 through the triple-coupled transformers Transformer3 and Transformer4; the isolation end of the quadrature coupler Coupler1 is connected to an isolation resistor to ground, and the input end of the quadrature coupler Coupler2 is connected to the transceiver antenna.

[0061] Furthermore, the CA path includes: a driver-stage amplifier DA and a power-stage amplifier CA. The driver-stage amplifier DA and the power-stage amplifier CA are connected in series. The input end of the driver-stage amplifier DA is connected to the output end of the power divider through a matching transformer, and the output end of the power-stage amplifier CA is connected to the isolation end of the quadrature coupler Coupler2 through a matching transformer.

[0062] Further, in the first bidirectional balanced branch, the BA1 path includes: a driver amplifier DA and a power amplifier BA1, and the LNA1 path includes: a driver amplifier DA and a low-noise amplifier LNA1; in the BA1 path, the driver amplifier DA and the power amplifier BA1 are connected in series. The input end of the driver amplifier DA in the BA1 path is connected to the tertiary coil of the triple-coupling transformer Transformer1, and the output end of the power amplifier BA1 in the BA1 path is connected to the tertiary coil of the triple-coupling transformer Transformer3; in the LNA1 path, the low-noise amplifier LNA1 and the driver amplifier DA are connected in series. The input end of the low-noise amplifier LNA1 in the LNA1 path is connected to the primary coil of the triple-coupling transformer Transformer3, and the output end of the driver amplifier DA in the LNA1 path is connected to the primary coil of the triple-coupling transformer Transformer1; the secondary coil of the triple-coupling transformer Transformer1 is connected to the through end of the quadrature coupler Coupler1, and the secondary coil of the triple-coupling transformer Transformer3 is connected to the coupled end of the quadrature coupler Coupler2.

[0063] Similarly, in the second bidirectional balanced branch, the BA2 path includes: a driver amplifier DA and a power amplifier BA2, and the LNA2 path includes: a driver amplifier DA and a low-noise amplifier LNA2; in the BA2 path, the driver amplifier DA and the power amplifier BA2 are connected in series. The input end of the driver amplifier DA in the BA2 path is connected to the tertiary coil of the triple-coupling transformer Transformer2, and the output end of the power amplifier BA2 in the BA2 path is connected to the tertiary coil of the triple-coupling transformer Transformer4; in the LNA2 path, the low-noise amplifier LNA2 and the driver amplifier DA are connected in series. The input end of the low-noise amplifier LNA2 in the LNA2 path is connected to the primary coil of the triple-coupling transformer Transformer4, and the output end of the driver amplifier DA in the LNA2 path is connected to the primary coil of the triple-coupling transformer Transformer2; the secondary coil of the triple-coupling transformer Transformer2 is connected to the coupled end of the quadrature coupler Coupler1, and the secondary coil of the triple-coupling transformer Transformer4 is connected to the through end of the quadrature coupler Coupler2.

[0064] As Figure 9 shown, when the circuit operates in the PA mode: the LNA circuit bias is set to zero. At this time, the input resistance of the LNA transistor is a large impedance. According to the analysis of the triple-coupling transformer, the triple-coupling transformer degenerates into a dual-coupling transformer at this time, and the coupling coefficient between the LNA coil and the primary coil is very low. The power mainly propagates through the PA path. The circuit operates as an LMBA in the PA mode.

[0065] The input signal first enters a power splitter. One path enters the CA path, and the other path enters the input end of the quadrature coupler Coupler1. Since the CA path is biased in Class-C, for small input signal power, the CA path does not work, and the power entering the quadrature coupler Coupler1 is divided into two signals with a 90° phase difference, which enter BA1 and BA2 respectively from the two output ends. The isolation end of the quadrature coupler Coupler1 is connected to a 50Ω impedance. The signals entering Bas (BA1 and BA2) are matched through a two-coupler transformer degenerated from a three-coupler transformer, amplified by DA and BA amplifiers, and finally reach the quadrature coupler Coupler2 at the output end respectively. Since the two BAs are exactly 90° out of phase, the output power is in-phase superimposed at the antenna end and out-of-phase cancelled at the CA end, and all the output power enters the antenna end and will not flow into the isolation end.

[0066] When the input signal gradually increases, first the BA path amplifier reaches saturation, and then the CA path will be turned on. After the CA path signal is matched through a transformer and amplified by the CA path amplifier, it flows into the isolation port of the output quadrature coupler. According to the above load modulation effect, it can be known that: the port impedance of the isolation end of the quadrature coupler Coupler1 is a constant value and equal to the characteristic impedance of the quadrature coupler. The port impedance of the quadrature coupler connected to the two BAs is controlled by the magnitude of the CA path current, the BA path current, and their phase difference α, and is specifically expressed as:

[0067]

[0068] From this, it can be seen that by setting appropriate current magnitude ratios and phase differences, the port impedance of the BA path is a real part that decreases as the CA path current increases, that is, load modulation is achieved.

[0069] As Figure 10 、 Figure 11 shown are the current and port impedance changes of the BA and CA paths respectively. Among them, the blue area is the low-power area, and only the BA path works in this area; the red area is the power back-off area, where the CA path is turned on, the port impedance of the BA path decreases as the CA path current increases, and at the same time the BA path current also increases, resulting in the expansion of the BA path output power; the green area is the saturation area, and both the BA and CA path amplifiers reach the saturation output current and saturation output power.

[0070] As Figure 12 、 Figure 13 shown are the gain curve and PAE curve of the two-way amplifier in the PA mode respectively. It can be seen from the figure that the two-way amplifier in the PA mode has a relatively flat gain curve, and the PAE is also very high within the 6dB back-off range.

[0071] As Figure 14As shown in the figure, when the circuit operates in the LNA mode: the bias of the PA circuit amplifier is set to zero, and the circuit structure is relatively simple at this time; the received signal enters from the antenna port, is divided into two signals with a 90° phase difference through the quadrature coupler, amplified by matching and the LNA, and then synthesized using the quadrature coupler; at the power divider position, since the CA path does not work, the corresponding port is equivalent to connecting a large impedance, enabling the signal to pass through the power divider almost without loss.

[0072] As Figure 15 , Figure 16 shown are the noise figure curve and the S21 curve of the bidirectional amplifier in the LNA mode respectively. As can be seen from the figure, the noise figure of the bidirectional amplifier in the LNA mode is relatively low, about 4.5, and the S21 curve is good.

[0073] As described above, it is only the specific implementation manner of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the disclosed features, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A bidirectional amplifier based on LMBA structure and three-coupled transformer, comprising: A power divider, orthogonal couplers Coupler1 and Coupler2, a CA path, a BA1 path, a BA2 path, an LNA1 path, an LNA2 path, and three coupling transformers Transformer1 to Transformer4; characterized in that: The BA1 path and the LNA1 path form a first bidirectional balanced branch, the BA2 path and the LNA2 path form a second bidirectional balanced branch, and the first bidirectional balanced branch and the second bidirectional balanced branch use the same circuit; The input end of the power divider serves as the input end of the PA mode and the output end of the LNA mode, one output of the power divider is connected to the CA path, and the output of the CA path is connected to the isolation end of the orthogonal coupler Coupler2; the other output of the power divider is connected to the input end of the orthogonal coupler Coupler1, and the orthogonal end of the orthogonal coupler Coupler1 is respectively connected to the first bidirectional balanced branch and the second bidirectional balanced branch through the three-coupling transformer Transformer1 and the three-coupling transformer Transformer2, and the first bidirectional balanced branch and the second bidirectional balanced branch are then connected to the orthogonal end of the orthogonal coupler Coupler2 through the three-coupling transformer Transformer3 and the three-coupling transformer Transformer4; the isolation end of the orthogonal coupler Coupler1 is connected to the isolation resistor to the ground, and the input end of the orthogonal coupler Coupler2 is connected to the transceiver antenna.

2. The bidirectional amplifier based on LMBA structure and three-coupled transformer according to claim 1, characterized in that: The CA circuit includes: a driver stage amplifier DA and a power stage amplifier CA, the driver stage amplifier DA and the power stage amplifier CA are connected in series, the input end of the driver stage amplifier DA is connected to the output end of the power divider through a matching transformer, and the output end of the power stage amplifier CA is connected to the isolation end of the orthogonal coupler Coupler2 through a matching transformer.

3. The bidirectional amplifier based on LMBA structure and three-coupled transformer according to claim 1, characterized in that: In the first bidirectional balanced branch, BA1 includes: a driver stage amplifier DA and a power stage amplifier BA1, and LNA1 includes: a driver stage amplifier DA and a low noise amplifier LNA1; in BA1, the driver stage amplifier DA and the power stage amplifier BA1 are connected in series, the input end of the driver stage amplifier DA in BA1 is connected to the tertiary coil of the three-coupled transformer Transformer1, and the output end of the power stage amplifier BA1 in BA1 is connected to the tertiary coil of the three-coupled transformer Transformer3; in LNA1, the low noise amplifier LNA1 is connected in series with the driver stage amplifier DA, the input end of the low noise amplifier LNA1 in LNA1 is connected to the primary coil of the three-coupled transformer Transformer3, and the output end of the driver stage amplifier DA in LNA1 is connected to the primary coil of the three-coupled transformer Transformer1; the secondary coil of the three-coupled transformer Transformer1 is connected to the through end of the orthogonal coupler Coupler1, and the secondary coil of the three-coupled transformer Transformer3 is connected to the coupling end of the orthogonal coupler Coupler2.

4. The bidirectional amplifier based on LMBA structure and three-coupled transformer according to claim 1, characterized in that: In the second bidirectional balanced branch, the BA2 path includes: a driver stage amplifier DA and a power stage amplifier BA2, and the LNA2 path includes: a driver stage amplifier DA and a low noise amplifier LNA2; the driver stage amplifier DA and the power stage amplifier BA2 in the BA2 path are connected in series, the input end of the driver stage amplifier DA in the BA2 path is connected to the tertiary coil of the three-coupled transformer Transformer2, and the output end of the power stage amplifier BA2 in the BA2 path is connected to the tertiary coil of the three-coupled transformer Transformer4; the low noise amplifier LNA2 and the driver stage amplifier DA in the LNA2 path are connected in series, the input end of the low noise amplifier LNA2 in the LNA2 path is connected to the primary coil of the three-coupled transformer Transformer4, and the output end of the driver stage amplifier DA in the LNA2 path is connected to the primary coil of the three-coupled transformer Transformer2; the secondary coil of the three-coupled transformer Transformer2 is connected to the coupling end of the orthogonal coupler Coupler1, and the secondary coil of the three-coupled transformer Transformer4 is connected to the through end of the orthogonal coupler Coupler2.

5. The bidirectional amplifier based on LMBA structure and three-coupled transformer according to claim 1, characterized in that: When the bidirectional amplifier operates in the PA mode, the LNA1 and LNA2 paths are biased to zero, the BA1 and BA2 paths are biased in the Class-AB mode, and the CA path is biased in the Class-C mode.

6. The bidirectional amplifier based on LMBA structure and three-coupled transformer according to claim 1, characterized in that: When the bidirectional amplifier operates in the LNA mode, the CA path, the BA1 path and the BA2 path are all biased to zero, and the LNA1 path and the LNA2 path are biased in the Class-A mode.

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