Low-loss Doherty efficiency enhanced load modulation balanced power amplifier and implementation method thereof

Abstract

The present invention discloses a low-loss Doherty efficiency enhanced load modulation balanced power amplifier and an implementation method thereof. The power amplifier comprises a non-equal input power divider module (1), a balanced power amplifier circuit module (2), a control signal power amplifier module (3) and a phase delay module (4); the balanced power amplifier circuit module (2) is a main path, and the control signal power amplifier module (3) is an auxiliary path, realizing the load modulation function of the auxiliary path to the main path; and an impedance converter is added to the main path to complete the load modulation function similar to that of the Doherty power amplifier. The present invention replaces the input coupler of a traditional load modulation balanced amplifier (LMBA) with a low-loss balanced power divider module to reduce signal transmission loss, replaces the dual input architecture of the traditional LMBA with a non-equal input power divider module to reduce system complexity, and adds an impedance converter to improve the efficiency of the LMBA within a fallback range.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless radio frequency circuits, and in particular to a low-loss Doherty efficiency enhanced load modulation balanced power amplifier and an implementation method thereof. Background Art

[0002] In recent years, the commercialization and development of the fifth generation mobile communication technology (5G) has allowed more people to experience the convenience brought by large bandwidth and high-speed information transmission, but it also occupies a large amount of spectrum resources. At present, the main frequency band of 5G is the Sub-6GHz band, and the spectrum resources in this band need to be more fully utilized. In order to efficiently use the increasingly scarce spectrum resources, high peak-to-average power ratio (PAPR) modulation signals are widely used. In order to ensure the high linearity requirements required for wireless communication quality, the power amplifier needs to often work in the back-off state and have high efficiency.

[0003] The power back-off method is equivalent to changing the transistor from a high-power output state to a low-power output state, which sacrifices DC power consumption excessively, resulting in reduced efficiency and heat dissipation difficulties. Therefore, it is necessary to take measures to maintain high efficiency in both saturation and back-off states, such as envelope tracking technology and Doherty's load modulation technology, but the narrowband characteristics of these technologies are increasingly unable to meet the current ultra-wideband wireless RF communication requirements, and a new broadband high back-off efficiency power amplifier architecture is needed to improve communication performance. The load-modulated balanced power amplifier (LMBA) proposed in recent years has shown its broadband characteristics, but the back-off efficiency has not yet achieved a performance improvement effect similar to Doherty's, and the complex dual-input architecture increases the complexity of the system. It is necessary to conduct research and provide solutions to address the defects in the existing technology. Summary of the invention

[0004] Technical problem: The purpose of the present invention is to provide a low-loss Doherty efficiency enhanced load-modulated balanced power amplifier and its implementation method, which can reduce the loss of traditional LMBA in signal transmission and further improve the efficiency within the back-off range.

[0005] Technical solution: A low-loss Doherty efficiency-enhanced load-modulated balanced power amplifier of the present invention comprises a non-equal input power divider module, a balanced power amplifier circuit module, a control signal power amplifier module and a phase delay module;

[0006] The balanced power amplifier circuit module is a main path, and includes a low-loss balanced power divider module, a second phase delay module, a power amplifier circuit module, an orthogonal coupler module, and a first impedance converter module, a second impedance converter module, and a third impedance converter module; wherein the power amplifier circuit module includes a second input match, a second power amplifier, a second output match, and a third input match, a third power amplifier, and a third output match;

[0007] The control signal power amplification module is an auxiliary circuit, including a first input match, a first power amplifier, and a first output match;

[0008] The non-equal input power divider module divides the input signal into two signals. The first signal passes through the phase delay module in sequence through the first input matching, the first power amplifier, and the first output matching end of the control signal power amplifier module, and then is output from the first output matching end to the third input port of the orthogonal coupler module; the second signal enters the low-loss balanced power divider module in the balanced power amplifier circuit module and is divided into two signals again. One signal passes through the second input matching of the power amplifier circuit module in sequence, and then passes through the second power amplifier, the second output matching end, the first impedance converter module to the first input port of the orthogonal coupler module, and the other signal passes through the second phase delay module in sequence through the third input matching of the power amplifier circuit module, the third power amplifier, the third output matching, the second impedance converter module to the third input port of the orthogonal coupler module; the output of the orthogonal coupler module outputs the signal through the third impedance converter module.

[0009] in,

[0010] The low-loss balanced power divider module is used to equally divide a signal into two completely identical signals, replacing the input coupler of a traditional balanced power amplifier.

[0011] A first impedance converter and a second impedance converter module are added between the power amplifier circuit module and the orthogonal coupler module. The first impedance converter module and the second impedance converter module are used to allow the second power amplifier and the third power amplifier to achieve a pre-saturation effect before the back-off range.

[0012] A broadband third impedance converter module is added between the orthogonal coupler module and the final output, and the third impedance converter module is used to convert the characteristic impedance of the orthogonal coupler module into 50Ω.

[0013] The low-loss balanced power divider module adopts an equally divided branch line power divider.

[0014] The power amplifier circuit module includes an input match, a power amplifier transistor and an output match connected in sequence; wherein the first power amplifier adopts a class C power amplifier, and the second power amplifier and the third power amplifier adopt class AB power amplifiers.

[0015] The unequal input power divider module adopts an unequal branch line power divider, and the second signal generated is 3dB larger than the first signal. It is different from the dual input structure of the traditional LMBA and reduces the complexity of the system.

[0016] The orthogonal coupler module adopts a 3dB orthogonal branch line coupler.

[0017] The method for implementing the low-loss Doherty efficiency enhanced load modulation balanced power amplifier of the present invention comprises the following steps:

[0018] S1. Design a low-loss balanced power divider module and add a 90° phase delay module at one of the output ends;

[0019] S2. Design a broadband 3dB orthogonal coupler module for the synthesis of main and auxiliary signals and the output of the total signal, and add a broadband second impedance converter at the output port of the orthogonal coupler module to convert the characteristic impedance of the coupler to 50Ω;

[0020] S3. Design a broadband balanced power amplifier circuit as the main path, wherein the output end of the second power amplifier is connected to the first input port of the designed orthogonal coupler, the output end of the third power amplifier is connected to the second input port of the designed orthogonal coupler, and the first impedance converter is adjusted to complete the load modulation effect similar to the Doherty power amplifier;

[0021] S4. Design a control signal power amplifier module as an auxiliary circuit, amplify the appropriate control signal, and connect it to the third input port of the designed orthogonal coupler;

[0022] S5. Design a broadband unequal input power divider module to split the input signal into two signals, and the second signal generated is 3dB larger than the first signal;

[0023] S6. Adjust the phase delay module between the generated first signal and the control signal power amplifier module to optimize the load modulation effect of the LMBA so that the overall effect meets the design requirements.

[0024] The present invention replaces the input coupler of a traditional balanced power amplifier with a low-loss balanced power divider module to reduce signal transmission loss; replaces the dual-input architecture of a traditional LMBA with a non-equal input power divider module, thereby greatly reducing the complexity of the system; and implements a method for improving the efficiency of a Doherty power amplifier by adding an impedance converter, thereby improving the efficiency of a load-modulated balanced power amplifier within a back-off range.

[0025] Beneficial effects: Compared with the traditional load modulation balanced amplifier, the present invention has the following advantages:

[0026] 1) Through the low-loss balanced power divider module, the system bandwidth is improved compared with the traditional coupler, and the system transmission loss is reduced. It also makes the two-way phase difference of the balanced power amplifier within the bandwidth more stable and close to 90°;

[0027] 2) The dual-input architecture of the traditional LMBA is replaced by a non-equal input power divider module, and the phase delay module is adjusted to achieve the load modulation effect of the LMBA, thereby greatly reducing the complexity of the system.

[0028] 3) The efficiency improvement method of the Doherty-like power amplifier is realized by adding an impedance transformer, thereby improving the efficiency of the load-modulated balanced power amplifier within the back-off range and improving the performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a system structure block diagram of the present invention;

[0030] Figure 2 is a structural block diagram of the orthogonal coupler in the present invention;

[0031] Figure 3 is a transmission loss comparison diagram of a conventional coupler and a low-loss power divider in a specific embodiment of the present invention;

[0032] Figure 4 is a phase loss comparison diagram of a conventional coupler and a low-loss power divider used in a specific embodiment of the present invention;

[0033] Figure 5 It is a comparison diagram of the ideal efficiency curve of the present invention and the traditional LMBA and traditional class AB power amplifier;

[0034] Figure 6 It is the final simulation result diagram in the specific design of the present invention.

[0035] The figure includes: a non-equal input power divider module 1, a balanced power amplifier circuit module 2, a control signal power amplifier module 3, and a phase delay module 4; a low-loss balanced power divider module 21, a second phase delay module 22, a power amplifier circuit module 23, an orthogonal coupler module 24, a first impedance converter module 251, a second impedance converter module 252, a third impedance converter module 253, a second input match 231, a second power amplifier 232, a second output match 233, a third input match 234, a third power amplifier 235, and a third output match 236; a first input match 31, a first power amplifier 32, and a first output match 33. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further introduced below in conjunction with specific implementation modes and drawings.

[0037] The power amplifier comprises an unequal input power divider module 1, a balanced power amplifier circuit module 2, a control signal power amplification module 3 and a phase delay module 4; the balanced power amplifier circuit module 2 is a main path, comprising a low-loss balanced power divider module 21, a second phase delay module 22, a power amplifier circuit module 23, an orthogonal coupler module 24 and a first impedance converter module 251, a second impedance converter module 252, and a third impedance converter module 253; wherein the power amplifier circuit module 23 comprises a second input match 231, a second power amplifier 232, a second output match 233 and a third input match 234, a third power amplifier 235, and a third output match 236; the control signal power amplification module 3 is an auxiliary path, comprising a first input match 31, a first power amplifier 32, and a first output match 33; the unequal input power divider module 1 divides the input signal into two signals, and the first signal passes through the phase delay module 4 in a sequential manner. The first signal passes through the first input matching 31, the first power amplifier 32, and the first output matching end 33 of the control signal power amplifier module 3, and then is output from the first output matching end 33 to the third input port of the orthogonal coupler module 24; the second signal enters the low-loss balanced power divider module 21 in the balanced power amplifier circuit module 2 and is divided into two signals, one signal passes through the second input matching 231 of the power amplifier circuit module 23 in sequence, and then passes through the second power amplifier 232, the second output matching end 233, and the first impedance converter module 251 to the first input port of the orthogonal coupler module 24, and the other signal passes through the second phase delay module 22 and passes through the third input matching 234, the third power amplifier 235, the third output matching 236, and the second impedance converter module 252 of the power amplifier circuit module 23 in sequence to the third input port of the orthogonal coupler module 24; the output of the orthogonal coupler module 24 outputs the signal through the third impedance converter module 253.

[0038] See also Figure 1 , which is a principle block diagram of a low-loss Doherty efficiency enhanced load-modulated balanced power amplifier of the present invention, comprising an unequal input power divider module 1, a balanced power amplifier circuit module 2, a control signal power amplifier module 3 and a phase delay module 4. The unequal input power divider module 1 divides the input signal into two signals, and the first signal passes through the first input matching 31, the first power amplifier 32, and the first output matching end 33 of the control signal power amplifier module 3 in sequence through the phase delay module 4, and then outputs from the first output matching end 33 to the third input port of the orthogonal coupler module 24, which serves as an auxiliary path;

[0039] The balanced power amplifier circuit module 2 is a main path, including a low-loss balanced power divider module 21, a second phase delay module 22, a power amplifier circuit module 23, an orthogonal coupler module 24, a first impedance converter module 251, a second impedance converter module 252, and a third impedance converter module 253; wherein the power amplifier circuit module 23 includes a second input match 231, a second power amplifier 232, a second output match 233 and a third input match 234, a third power amplifier 235, and a third output match 236; the second path signal enters the low-loss balanced power divider module 2 in the balanced power amplifier circuit module 2 1 is further divided into two signals, one signal passes through the second input matching 231 of the power amplifier circuit module 23 in sequence, and then passes through the second power amplifier 232, the second output matching end 233, the first impedance converter module 251 to the first input port of the orthogonal coupler module 24, and the other signal passes through the second phase delay module 22 in sequence, passes through the third input matching 234 of the power amplifier circuit module 23, the third power amplifier 235, the third output matching 236, the second impedance converter module 252 to the third input port of the orthogonal coupler module 24; the output of the orthogonal coupler module 24 outputs a signal through the third impedance converter module 253.

[0040] As a further improvement, the low-loss balanced power divider module 21 is used to divide the signal into two completely identical signals, replacing the input coupler of a traditional balanced power amplifier.

[0041] Furthermore, a first impedance converter 251 and a second impedance converter module 252 are added between the power amplifier circuit module 23 and the orthogonal coupler module 24. The first impedance converter module 251 and the second impedance converter module 252 are used to allow the second power amplifier 232 and the third power amplifier 235 to achieve a pre-saturation effect before the back-off range.

[0042] Furthermore, a broadband third impedance converter module 253 is added between the orthogonal coupler module 24 and the final output, and the third impedance converter module 253 is used to convert the characteristic impedance of the orthogonal coupler module 24 into 50Ω.

[0043] Furthermore, the power amplifier circuit module 23 includes an input match, a power amplifier transistor and an output match connected in sequence; wherein the first power amplifier 32 adopts a class C power amplifier, and the second power amplifier 232 and the third power amplifier 235 adopt class AB power amplifiers.

[0044] Furthermore, the unequal input power divider module 1 adopts an unequal branch line power divider, and the second signal generated is 3dB larger than the first signal, which is different from the dual input structure of the traditional LMBA and reduces the complexity of the system.

[0045] Finally, the main path and the auxiliary path are connected through the orthogonal coupler module 24 and output at the 4th port of the orthogonal coupler module 24. After passing through the third impedance converter module 253, the output is output to the standard load of 50Ω, and a complete low-loss Doherty efficiency enhanced load modulation balanced power amplifier architecture is built.

[0046] The technical principle of the low-loss Doherty efficiency enhanced load modulation balanced power amplifier of the present invention is further described as follows:

[0047] like Figure 2 , a schematic diagram of the orthogonal coupler module 24 is shown, I 1 ,I 2 ,I 3 and I 4 are the equivalent currents of the first, second, third and fourth ports of the orthogonal coupler module 24; V 1 、V 2 、V 3 and V 4 are the equivalent voltages of the 1st, 2nd, 3rd and 4th ports of the orthogonal coupler module 24 respectively; Z 0 is the characteristic impedance of the orthogonal coupler module 24; j is the sign of the imaginary part; the current flowing out of the first power amplifier 32 is I C ; The current flowing out of the second power amplifier 232 is I AB The phase difference between the current at the third port of the orthogonal coupler module 24 and the current at the first port is Φ, and the scattering parameter matrix of the orthogonal coupler module 24 is:

[0048]

[0049] Then I 1 =-jI AB ,I 2 =-IAB ,I 3 =-jI C e jΦ ,

[0050] According to the scattering parameter matrix of the orthogonal coupler module 24, the impedance of the second amplifier transistor and the third amplifier transistor looking at the port 1 and the port 2 of the orthogonal coupler module 24 is Z 1 and Z 2 :

[0051]

[0052] The power expression of each port can be calculated based on impedance, voltage and current. The output power of the first amplifier transistor is P C The output power of the second amplifier transistor is P AB1 , the output power of the third amplifier transistor is P AB2 , their relationship is:

[0053]

[0054]

[0055] In the formula, Re is the real part operator. According to the scattering parameter matrix, the equivalent current of the fourth port of the orthogonal coupler module 24 is I 4 :

[0056]

[0057] The total output P out The relationship with the output of the three-way power amplifier transistor is as follows:

[0058]

[0059] It can be seen that the outputs of the three power amplifier transistors can all be output to the fourth port of the orthogonal coupler module 24, without any loss in theory.

[0060] The low-loss Doherty efficiency enhanced load modulation balanced power amplifier architecture presents different load modulation modes in the low-power signal stage before the back-off point and the high-power signal stage after the back-off point.

[0061] In the low power signal stage before the back-off point, the first power amplifier 32 operates in Class C and does not amplify the signal and is close to the off state, so I 3=0, the output power of the entire power amplifier is completely provided by the balanced power amplifier circuit module 2. The characteristic impedance of the branch line orthogonal coupler module 24 used in this design is 20Ω, and the first impedance converter module 251 and the second impedance converter module 252 are quarter-wavelength impedance converters with a characteristic impedance of 47Ω. The characteristic impedance of the orthogonal coupler module 24 is converted into a high-impedance state of 110Ω, and then presented to the amplifier transistor through the matching network, so as to achieve the effect of saturating the power amplifier transistor in advance, so as to greatly improve the efficiency of the back-off point. This is one of the principles of the Doherty power amplifier.

[0062] In the high-power signal stage after the back-off point, the first power amplifier 32 working in class C is gradually turned on to play the role of power amplification, and the load modulation effect of LMBA begins to appear. At this time, the impedance of the first port and the second port of the orthogonal coupler module 24 relative to the second power amplifier 232 and the third power amplifier 235 will no longer be Z due to the effect of load modulation. 0 =20Ω, and becomes:

[0063]

[0064] As the control path signal power increases, a power ratio factor α is defined:

[0065]

[0066] At this time, the reflection coefficients ρ of the first port and the second port of the orthogonal coupler module 24 are 1 and ρ 2 The same, both are reflection coefficient ρ:

[0067]

[0068] From this, we can deduce the relationship between the power ratio factor and the reflection coefficient:

[0069]

[0070] Therefore, by reasonably setting the value of the power ratio factor α, the amplitude modulation function of the LMBA can be achieved, and by reasonably setting the value of the phase difference Φ in the phase delay module 4, the phase modulation function of the LMBA can be achieved. Finally, at the saturation point, the power ratio factor is set to the ratio of the saturated output of the first power amplifier 32 to the saturated output of the second power amplifier 232. At this time, α=0.686. By changing the phase delay module 4, the saturation state can achieve the highest efficiency, realizing the load modulation function of the LMBA; through the load modulation of the LMBA, Z 1 and Z 2The impedance is modulated to 62Ω, and then transformed to 35.5Ω by the first impedance converter module 251 and the second impedance converter module 252, so that the power amplifier transistor can be changed from the pre-saturation state to the normal saturation state, realizing the Doherty load modulation function.

[0071] In summary, the low-loss Doherty efficiency enhanced load-modulated balanced power amplifier of the present application has the following three advantages compared to the traditional load-modulated balanced amplifier:

[0072] 1) Through the low-loss balanced power divider module, the system bandwidth is improved compared with the traditional coupler, and the system transmission loss is reduced. It also makes the two-way phase difference of the balanced power amplifier within the bandwidth more stable and close to 90°;

[0073] 2) The dual-input architecture of the traditional LMBA is replaced by a non-equal input power divider module, and the phase delay module is adjusted to achieve the load modulation effect of the LMBA, thereby greatly reducing the complexity of the system.

[0074] 3) The efficiency improvement method of the Doherty-like power amplifier is realized by adding an impedance transformer, thereby improving the efficiency of the load-modulated balanced power amplifier within the back-off range and improving the performance of the system.

[0075] The design of the low-loss Doherty efficiency enhanced load modulation balanced power amplifier of the present invention comprises the following steps:

[0076] S1. Design a low-loss balanced power divider module and add a 90° phase delay module to one of the output ends. Compare it with the traditional coupler. Figure 3 and Figure 4 In the range of 3.2GHz-3.8GHz, the transmission loss is the difference between the transmission coefficient and 3dB. The transmission loss is reduced from 1.1dB-0.1dB to 0.07dB-0.04dB, and the loss reduction effect is significant. The phase loss is the difference between the two-way phase difference and the standard 90°. The phase loss is reduced from -18.5° to 11°, and the phase loss is significantly reduced.

[0077] S2. Design a broadband 3dB orthogonal coupler module for main and auxiliary signal synthesis and total signal output, and add a broadband second impedance converter at the fourth port of the coupler to convert the characteristic impedance of the coupler to 50Ω;

[0078] S3. Design a broadband balanced power amplifier circuit as the main circuit, in which the AB class power amplifier transistor is 10W-CG2H40010F produced by CREE, the drain voltage is set to 28V, and the gate voltage is set to -2.8V. On this basis, the input matching, output matching and DC bias circuits are designed to match the transistor source impedance to 50Ω, and the optimal load impedance of the transistor saturation point is matched to 35.5Ω. The output end of the second power amplifier is connected to the first port of the designed orthogonal coupler, and the output end of the third power amplifier is connected to the second port of the designed orthogonal coupler, and the first impedance converter is adjusted to complete the load modulation function similar to the Doherty power amplifier;

[0079] S4. Design a control signal power amplifier module as an auxiliary circuit to amplify the appropriate control signal. The C-class power amplifier transistor is 10W-CG2H40010F produced by CREE. The drain voltage is set to 28V and the gate voltage is set to -6.5V. On this basis, design the input matching, output matching and DC bias circuits, match the transistor source impedance to 50Ω, match the optimal load impedance of the transistor saturation point to the characteristic impedance of the coupler 20Ω, and connect it to the third port of the designed orthogonal coupler.

[0080] S5. Design a broadband non-uniform input power divider module to divide the input signal into two signals. The second signal generated is stronger than the first signal.

[0081] The signal is 3dB louder;

[0082] S6, adjusting the phase delay module between the generated first signal and the control signal power amplifier module, optimizing the load modulation effect of the LMBA, and finally selecting a 160° phase delay module so that the overall effect meets the design requirements;

[0083] Following the above steps, a complete low-loss Doherty efficiency enhanced load modulation balanced power amplifier can be designed. Its ideal efficiency curve is compared with the traditional LMBA and traditional AB class power amplifier. Figure 5 As shown in Figure 1, its efficiency improvement capability is significant. A complete low-loss Doherty efficiency enhanced load modulation balanced power amplifier designed based on the method of the present invention using ADS software has a simulation result as shown in Figure 1. Figure 6 As shown, the efficiency when the power is backed off by 6 dB is increased to 57% (the traditional AB class is generally around 35%, and the traditional LMBA is generally around 51%), and the saturation efficiency reaches 67%, showing good efficiency improvement performance.

Claims

1. A low-loss Doherty efficiency enhanced load modulation balanced power amplifier, characterized in that: The power amplifier comprises a non-equal input power divider module (1), a balanced power amplifier circuit module (2), a control signal power amplification module (3) and a phase delay module (4); The balanced power amplifier circuit module (2) is a main path, comprising a low-loss balanced power divider module (21), a second phase delay module (22), a power amplifier circuit module (23), an orthogonal coupler module (24), a first impedance converter module (251), a second impedance converter module (252), and a third impedance converter module (253); wherein the power amplifier circuit module (23) comprises a second input match (231), a second power amplifier (232), a second output match (233), a third input match (234), a third power amplifier (235), and a third output match (236); The control signal power amplification module (3) is an auxiliary circuit, comprising a first input match (31), a first power amplifier (32), and a first output match (33); The non-uniform input power splitter module (1) splits the input signal into two signals. The first signal passes through the phase delay module (4) and sequentially passes through the first input matching (31), the first power amplifier (32), and the first output matching end (33) of the control signal power amplifier module (3), and then is output from the first output matching end (33) to the third input port of the orthogonal coupler module (24); the second signal enters the low-loss balanced power splitter module (21) in the balanced power amplifier circuit module (2) and is then split into two signals. One signal sequentially passes through the second input matching (23) of the power amplifier circuit module (23). 1), then passes through the second power amplifier (232), the second output matching end (233), the first impedance converter module (251) to the first input port of the orthogonal coupler module (24), and the other signal passes through the second phase delay module (22) in sequence through the third input matching (234) of the power amplifier circuit module (23), the third power amplifier (235), the third output matching (236), the second impedance converter module (252) to the third input port of the orthogonal coupler module (24); the output of the orthogonal coupler module (24) outputs a signal through the third impedance converter module (253); The low-loss balanced power divider module (21) is used to equally divide a signal into two completely identical signals, replacing the input coupler of a traditional balanced power amplifier; A first impedance converter (251) and a second impedance converter module (252) are added between the power amplifier circuit module (23) and the orthogonal coupler module (24), wherein the first impedance converter module (251) and the second impedance converter module (252) are used to allow the second power amplifier (232) and the third power amplifier (235) to achieve a pre-saturation effect before the fallback range; A broadband third impedance converter module (253) is added between the orthogonal coupler module (24) and the final output, and the third impedance converter module (253) is used to convert the characteristic impedance of the orthogonal coupler module (24) into 50Ω; The unequal input power divider module (1) adopts an unequal branch line power divider, and the second signal generated is 3 dB larger than the first signal, which is different from the dual input structure of the traditional LMBA and reduces the complexity of the system.

2. The low-loss Doherty efficiency enhanced load modulation balanced power amplifier according to claim 1, characterized in that: The low-loss balanced power divider module (21) adopts an equally divided branch line power divider.

3. The low-loss Doherty efficiency enhanced load-modulated balanced power amplifier according to claim 1, characterized in that: The power amplifier circuit module (23) comprises an input match, a power amplifier transistor and an output match connected in sequence; wherein the first power amplifier (32) adopts a class C power amplifier, and the second power amplifier (232) and the third power amplifier (235) adopt class AB power amplifiers.

4. The low-loss Doherty efficiency enhanced load-modulated balanced power amplifier according to claim 1, characterized in that: The orthogonal coupler module (24) adopts a 3dB orthogonal branch line coupler.

5. A method for implementing the low-loss Doherty efficiency enhanced load modulation balanced power amplifier as claimed in claim 1, characterized in that: The following steps are involved: S1. Design a low-loss balanced power divider module and add a 90° phase delay module at one of the output ends; S2. Design a broadband 3dB orthogonal coupler module for the synthesis of main and auxiliary signals and the output of the total signal, and add a broadband second impedance converter at the output port of the orthogonal coupler module to convert the characteristic impedance of the coupler to 50Ω; S3. Design a broadband balanced power amplifier circuit as the main path, wherein the output end of the second power amplifier is connected to the first input port of the designed orthogonal coupler, the output end of the third power amplifier is connected to the second input port of the designed orthogonal coupler, and the first impedance converter is adjusted to complete the load modulation effect similar to the Doherty power amplifier; S4. Design a control signal power amplifier module as an auxiliary circuit, amplify the appropriate control signal, and connect it to the third input port of the designed orthogonal coupler; S5. Design a broadband unequal input power divider module to split the input signal into two signals, and the second signal generated is 3dB larger than the first signal; S6. Adjust the phase delay module between the generated first signal and the control signal power amplifier module to optimize the load modulation effect of the LMBA so that the overall effect meets the design requirements.

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