A load modulation balanced power amplifier and design method thereof

Abstract

The present invention discloses a load-modulated balanced power amplifier and a design method, and the specific implementation steps are as follows: 1. Determine the current surface saturation current value and the optimal load impedance value of the selected transistor through load pulling; 2. Calculate the coupler surface impedance value at saturation according to the single-tube saturation power ratio; 3. Design a broadband single-tube carrier power amplifier and a broadband single-tube balanced power amplifier respectively; 4. Calculate the phase difference reference value within the frequency band according to the coupler surface current ratio and the coupler surface impedance value; 5. According to the phase difference reference value and comprehensive consideration of various performance indicators, the actual value of the phase shift is finally obtained through optimization, and the design of a broadband and high back-off efficiency load-modulated balanced power amplifier is realized. The present invention solves the problem that the amplitude and phase shift of the control path signal are difficult to accurately predict in the traditional design method, and provides a novel idea for the design of a broadband high back-off efficiency load-modulated balanced power amplifier.

Description

Technical Field

[0001] The invention relates to the field of radio frequency power amplifier circuit design, and in particular to a simplified design method for a load-modulated balanced power amplifier. Background Art

[0002] In modern wireless communication systems, modulation signals with a high peak-to-average power ratio are usually used to optimize spectrum efficiency and make full use of spectrum resources, but this requires the power amplifier to maintain a high working efficiency within a large output power back-off range. Traditional energy regulation technology faces many difficulties in efficiently transmitting high peak-to-average power ratio signals and expanding to a wider bandwidth. However, as a high-efficiency power amplifier architecture with multiple transistors participating in load modulation, the load-modulated balanced power amplifier can take into account both wide bandwidth and high back-off efficiency, so it has become a better choice. The basic principle of the load-modulated balanced power amplifier is to inject the control path signal into the balanced power amplifier through the isolation port of the output coupler. By adjusting the amplitude and phase offset of the control signal level, the load impedance seen by the balanced power amplifier can be modulated to fit the optimal load impedance trajectory, thereby achieving excellent back-off efficiency performance within a large output power back-off range. In addition, the hybrid coupler as a load modulation network of the load-modulated balanced power amplifier helps to expand the frequency band while maintaining high back-off efficiency.

[0003] The difficulty in designing a broadband high back-off efficiency load-modulated balanced power amplifier lies in setting a reasonable power ratio and phase difference between the control path signal and the balanced path signal. In the traditional load-modulated balanced power amplifier design method, the optimal phase offset of the control path signal level is usually obtained by scanning the phase difference between the control path power amplifier (CA) and the balanced path power amplifier (BA1, BA2). This method that relies on parameter scanning is quite complex and computationally intensive. At present, there is still a relative lack of design guidance and optimization methods for broadband high back-off efficiency load-modulated balanced power amplifiers. Summary of the invention

[0004] Technical problem: The purpose of the present invention is to propose a load-modulated balanced power amplifier and a design method. In view of the problems of difficulty in band widening and low back-off efficiency caused by the lack of precise design guidance on the amplitude and phase offset of the control path signal level in the design process of the existing load-modulated balanced power amplifier, the method proposed in the present invention focuses on the optimization of the control signal level, provides a straightforward reference for the value of the phase offset, and simplifies the design process of a broadband load-modulated balanced power amplifier with high back-off efficiency.

[0005] Technical solution: To solve the above technical problems, the present invention proposes a simplified design method for a load-modulated balanced power amplifier, which adopts the following technical solution:

[0006] The load modulated balanced power amplifier of the present invention comprises a hybrid coupler, a control path power amplifier circuit module, a phase shift module including a first phase shift module and a second phase shift module, and a balanced path power amplifier circuit module; the hybrid coupler divides a radio frequency input signal into two paths, namely a control path signal and a balanced path signal; the control path power amplifier circuit module amplifies the control path signal from the hybrid coupler, and then outputs the amplified control path signal to the second phase shift module; the first phase shift module and the second phase shift module determine the phase shift between the control path signal and the balanced path signal, and reasonably set the phase difference between the two signals to ensure the broadband characteristics and high back-off efficiency of the load modulated balanced power amplifier; the balanced path power amplifier circuit module comprises an input end hybrid coupler, a first balanced power amplifier, a second balanced power amplifier, and an output end hybrid coupler, the input end hybrid coupler divides the balanced path signal into two paths, and then injects them into the first balanced power amplifier and the second balanced power amplifier respectively, the output end hybrid coupler receives the output signals of the first balanced power amplifier and the second balanced power amplifier for hybrid amplification, and finally merges the amplified balanced path signal and the control path signal injected from the second phase shift module into a total output signal.

[0007] The hybrid coupler equally divides a single input radio frequency signal into two signals with the same amplitude and a phase difference of 90°, namely a control signal and a balanced signal.

[0008] The control path power amplifier circuit module comprises a control path power amplifier input matching network, a control path power amplifier transistor, and a control path power amplifier output matching network; the base of the control path power amplifier transistor is connected to the control path power amplifier input matching network, and the collector of the control path power amplifier transistor is connected to the control path power amplifier output matching network.

[0009] The control path power amplifier transistor selects a gallium nitride transistor with suitable output power as the control path power amplifier transistor according to needs, finds the optimal source impedance value and the optimal load impedance value through source pull simulation and load pull simulation, and the input and output port impedances of the control path power amplifier circuit module are both 50Ω, thereby setting the control path power amplifier input matching network and the control path power amplifier output matching network.

[0010] The first phase shift module and the second phase shift module change the load impedance values ​​of the first balanced power amplifier and the second balanced power amplifier by affecting the phase shift between the control path signal and the balanced path signal, and achieve the purpose of fitting the optimal load impedance trajectory by providing a suitable phase difference within the frequency band, thereby achieving higher drain efficiency within a larger output power back-off range.

[0011] The first balanced power amplifier includes a first balanced power amplifier input matching network, a first balanced power amplifier transistor, and a first balanced power amplifier output matching network; the base of the first balanced power amplifier transistor is connected to the output end of the first balanced power amplifier input matching network, and the collector of the first balanced power amplifier transistor is connected to the first balanced power amplifier output matching network.

[0012] The second balanced power amplifier includes a second balanced power amplifier input matching network, a second balanced power amplifier transistor, and a second balanced power amplifier output matching network; the base of the second balanced power amplifier transistor is connected to the output end of the second balanced power amplifier input matching network, and the collector of the second balanced power amplifier transistor is connected to the second balanced power amplifier output matching network.

[0013] The input end hybrid coupler and the output end hybrid coupler in the balanced power amplifier circuit module both adopt 3-dB orthogonal couplers which respectively play the role of power distribution and power synthesis; the first balanced power amplifier and the second balanced power amplifier both adopt the same input matching and output matching networks to ensure that the phases of the two signals are consistent when they arrive at the output end hybrid coupler.

[0014] In addition, considering various factors such as efficiency and back-off range, the first balanced power amplifier transistor and the second balanced power amplifier transistor both use gallium nitride transistors with a larger output power than the control path power amplifier transistor.

[0015] A design method for a load-modulated balanced power amplifier of the present invention is based on the load-modulated balanced power amplifier. First, the saturation current ratio and the load impedance value at the output hybrid coupler port are derived, and then the required reference phase difference is calculated. Finally, the phase offset value of the control path power amplifier circuit module is optimized to achieve widened bandwidth and high back-off efficiency, thereby completing the design of the load-modulated balanced power amplifier.

[0016] The design method comprises the following steps:

[0017] S1: Obtain the optimal load impedance value Z of the control path power amplifier circuit module through load pull simulation CA，opt The impedance value of the control path power amplifier circuit module at the output hybrid coupler port is approximately constant at 50Ω, and the saturation current I at the output coupler plane is further obtained. CA，max ;

[0018] S2: Define α as the single-tube saturation power ratio between the control-path power amplifier circuit module and the balanced-path power amplifier circuit module. To achieve a 10-dB output power back-off range, calculate the expected power ratio α to be 2 / 9. Then, derive the load impedance value Z of the balanced-path power amplifier circuit module at the output hybrid coupler port according to the formula. BA ;

[0019] S3: Obtain the optimal load impedance Z of the balanced power amplifier circuit module through load-pull simulation BA,opt ; Due to Z BA,opt and Z BA The value of is known, so after completing the design of the balanced power amplifier circuit module independently, find the saturation current value I at the output hybrid coupler port BA，max ;

[0020] S4: Define Z 0 is the characteristic impedance value of the hybrid coupler, θ is the phase difference between the control path signal and the balanced path signal, according to the formula Calculate the reference value of the phase difference θ 参考值 is a function of frequency;

[0021] S5: With θ 参考值 As a reference for optimization, the overall circuit design of the load-modulated balanced power amplifier is completed, and the various indicators of broadband effect and back-off efficiency are comprehensively considered to obtain the actual optimal value θ of the simulated phase offset 实际值 , ultimately achieving excellent performance of broadband high back-off efficiency;

[0022] S6: Verify the design and optimization method through physical processing and actual testing.

[0023] Beneficial effect: Compared with the prior art, the present invention proposes a load-modulated balanced power amplifier and a design method. In view of the problems in the design process of the existing load-modulated balanced power amplifier, such as difficulty in band widening and low back-off efficiency due to the lack of precise design guidance on the amplitude and phase offset of the control path signal level, the method proposed in the present invention focuses on the optimization of the control signal level, provides a straightforward reference for the value of the phase offset, and simplifies the design process of a broadband load-modulated balanced power amplifier with high back-off efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a simplified design method for a load-modulated balanced power amplifier in a specific implementation manner of the present invention.

[0025] Figure 2The following is a circuit topology diagram of a load-modulated balanced power amplifier designed according to the simplified method in a specific implementation manner of the present invention.

[0026] Figure 3 The figure is a comparison diagram between a phase shift reference value and an actual phase shift value of a control path signal level obtained according to the simplified design method in a specific implementation manner of the present invention.

[0027] Figure 4 It is a coupler planar impedance trajectory of a control path power amplifier and a balanced path power amplifier obtained by simulation that changes with the increase of output power at different frequencies in a specific implementation manner of the present invention.

[0028] Figure 5 It is a current plane impedance trajectory of a control path power amplifier and a balanced path power amplifier obtained by simulation that changes with the increase of output power at different frequencies in a specific implementation manner of the present invention.

[0029] Figure 6 The following are simulation results of the relationship between drain efficiency and gain and output power of a 2.0 GHz to 2.8 GHz load modulated balanced power amplifier designed according to the simplified design method in a specific implementation manner of the present invention.

[0030] Figure 7 The present invention is specifically described in detail with reference to the actual measured results of the relationship between the drain efficiency and the gain and the output power of a 2.0 GHz to 2.8 GHz load modulated balanced power amplifier designed according to the simplified design method.

[0031] The figure includes: a hybrid coupler 1, a control path power amplifier circuit module 2, a control path power amplifier input matching network 21, a control path power amplifier transistor 22, a control path power amplifier output matching network 23, a first phase shift module 31, a second phase shift module 32, a balanced path power amplifier circuit module 4, an input end hybrid coupler 41, a first balanced power amplifier 42, a second balanced power amplifier 43, an output end hybrid coupler 44, a first balanced path power amplifier input matching network 421, a first balanced path power amplifier transistor 422, a first balanced path power amplifier output matching network 423, a second balanced path power amplifier input matching network 431, a second balanced path power amplifier transistor 432, and a second balanced path power amplifier output matching network 433. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further introduced in conjunction with specific implementation methods and drawings.

[0033] The described design method is based on the basic principle of load modulated balanced power amplifier.

[0034] Since the amplitude and phase shift of the control signal power have a significant impact on the output power back-off range and back-off efficiency of the load-modulated balanced power amplifier, the simplified method proposed in the present invention focuses on optimizing the control signal level.

[0035] Figure 2 The circuit topology diagram of the load modulated balanced power amplifier designed according to the simplified method is shown. The power amplifier includes a hybrid coupler 1, a control path power amplifier circuit module 2, a phase shift module including a first phase shift module 31 and a second phase shift module 32, and a balanced path power amplifier circuit module 4; the hybrid coupler 1 divides the RF input signal into two equal paths, namely a control path signal and a balanced path signal; the control path power amplifier circuit module 2 amplifies the control path signal from the hybrid coupler 1, and then outputs the amplified control path signal to the second phase shift module 32; the first phase shift module 31 and the second phase shift module 32 determine the phase shift between the control path signal and the balanced path signal, and reasonably set the phase difference of the two signals to ensure The load-modulated balanced power amplifier has broadband characteristics and high back-off efficiency; the balanced power amplifier circuit module 4 includes an input hybrid coupler 41, a first balanced power amplifier 42, a second balanced power amplifier 43, and an output hybrid coupler 44. The input hybrid coupler 41 divides the balanced signal into two equal paths, and then injects them into the first balanced power amplifier 42 and the second balanced power amplifier 43 respectively. The output hybrid coupler 44 receives the output signals of the first balanced power amplifier 42 and the second balanced power amplifier 43 for hybrid amplification, and finally combines the amplified balanced signal and the control signal injected from the second phase shift module 32 into a total output signal.

[0036] The hybrid coupler 1 equally divides a single input radio frequency signal into two signals with the same amplitude and a phase difference of 90°, namely a control signal and a balanced signal.

[0037] The control path power amplifier circuit module 2 includes a control path power amplifier input matching network 21, a control path power amplifier transistor 22, and a control path power amplifier output matching network 23; the base of the control path power amplifier transistor 22 is connected to the control path power amplifier input matching network 21, and the collector of the control path power amplifier transistor 22 is connected to the control path power amplifier output matching network 23. The control path power amplifier transistor 22 selects a gallium nitride transistor with suitable output power as the control path power amplifier transistor according to the needs, and finds the optimal source impedance value and the optimal load impedance value through source pull simulation and load pull simulation. The input and output port impedances of the control path power amplifier circuit module 2 are both 50Ω, thereby setting the control path power amplifier input matching network 21 and the control path power amplifier output matching network 23.

[0038] The first phase shift module 31 and the second phase shift module 32 change the load impedance values ​​of the first balanced power amplifier 42 and the second balanced power amplifier 43 by affecting the phase shift between the control path signal and the balanced path signal, and achieve the purpose of fitting the optimal load impedance trajectory by providing a suitable phase difference within the frequency band, thereby achieving higher drain efficiency within a larger output power back-off range.

[0039] The input hybrid coupler 41 and the output hybrid coupler 44 in the balanced power amplifier circuit module 4 both use 3-dB orthogonal couplers that play the role of power distribution and power synthesis respectively; the first balanced power amplifier 42 and the second balanced power amplifier 43 both use the same input matching and output matching networks to ensure that the phases of the two signals are consistent when they reach the output hybrid coupler 44.

[0040] The first balanced power amplifier 42 includes a first balanced power amplifier input matching network 421, a first balanced power amplifier transistor 422, and a first balanced power amplifier output matching network 423; the base of the first balanced power amplifier crystal 422 is connected to the output end of the first balanced power amplifier input matching network 421, and the collector of the first balanced power amplifier transistor 422 is connected to the first balanced power amplifier output matching network 423.

[0041] The second balanced power amplifier 43 includes a second balanced power amplifier input matching network 431, a second balanced power amplifier transistor 432, and a second balanced power amplifier output matching network 433; the base of the second balanced power amplifier transistor 432 is connected to the output end of the second balanced power amplifier input matching network 431, and the collector of the second balanced power amplifier transistor 432 is connected to the second balanced power amplifier output matching network 433.

[0042] The power amplifier circuit topology designed according to the method includes a hybrid coupler, a control path power amplifier circuit module, a phase shift module and a balanced path power amplifier circuit module. After the RF input signal enters the 3-dB orthogonal coupler, it is divided into two RF signals of equal size and 90° phase difference. The control path power amplifier circuit module amplifies the power of the RF signal entering the control path, and the module includes a control path power amplifier input matching network, a control path power amplifier transistor, and a control path power amplifier output matching network. The length of the phase shift line determines the phase difference between the control path signal and the balanced path signal. Reasonable setting of the phase difference between the two signals ensures the broadband characteristics and high back-off efficiency of the load-modulated balanced path power amplifier. The function of the hybrid coupler at the input end of the balanced path power amplifier circuit module is to divide the control path signal into two equal paths, and then inject them into the balanced power amplifier and the balanced power amplifier respectively. The function of the output end hybrid coupler is to merge the amplified balanced path signal and the control path signal injected from the isolation port into a total output signal.

[0043] like Figure 1 As shown, the simplified design method of a load-modulated balanced power amplifier mainly includes the following specific steps:

[0044] 1. Determine the current plane saturation current value and the optimal load impedance value of the selected transistor through load pulling;

[0045] 2. Calculate the output coupler surface impedance value at saturation based on the single tube saturation power ratio;

[0046] 3. Design a broadband single-tube control-path power amplifier and a broadband single-tube balanced-path power amplifier respectively;

[0047] 4. Calculate the phase difference reference value within the frequency band from the coupler surface current ratio and the coupler surface impedance value;

[0048] 5. Based on the phase difference reference value and comprehensive consideration of various performance indicators, the actual value of the phase shift is finally obtained through optimization to achieve performance such as broadband and high back-off efficiency;

[0049] 6. Verify the simplified design and optimization method through physical processing and actual testing.

[0050] The design method specifically comprises the following steps:

[0051] S1: Obtain the optimal load impedance value Z of the control path power amplifier circuit module 2 through load pull simulation CA，opt The impedance value of the control path power amplifier circuit module 2 at the output end hybrid coupler 44 port is constant at 50Ω, and the saturation current I at the output end coupler plane is further obtained. CA，max ;

[0052] S2: Define α as the single-tube saturation power ratio between the control-path power amplifier circuit module 2 and the balanced-path power amplifier circuit module 4. To achieve a 10-dB output power back-off range, calculate the expected power ratio α to be 2 / 9, and then derive the load impedance value Z of the balanced-path power amplifier circuit module 4 at the output hybrid coupler 44 port according to the formula. BA ;

[0053] S3: Obtain the optimal load impedance Z of the balanced power amplifier circuit module 4 through load-pull simulation BA,opt ; Due to Z BA,opt and Z BA The value of is known, so after independently completing the design of the balanced power amplifier circuit module (4), the saturation current value I at the output hybrid coupler 44 port is calculated. BA，max ;

[0054] S4: Define Z 0 is the characteristic impedance value of the hybrid coupler, θ is the phase difference between the control path signal and the balanced path signal, according to the formula Calculate the reference value of the phase difference θ 参考值 is a function of frequency;

[0055] S5: With θ 参考值 As a reference for optimization, the overall circuit design of the load-modulated balanced power amplifier is completed, and the various indicators of broadband effect and back-off efficiency are comprehensively considered to obtain the actual optimal value θ of the simulated phase offset 实际值 , ultimately achieving excellent performance of broadband high back-off efficiency;

[0056] S6: Verify the design and optimization method through physical processing and actual testing.

[0057] The gate voltage of the control path power amplifier is -2.8V, working in class AB state. The drain voltage is 14V, which is lower than the transistor reference voltage. The setting changes the saturated output power of the control path power amplifier, which is conducive to improving the drain efficiency and expanding the output power back-off range.

[0058] In order to obtain the saturated fundamental current value I of the control path power amplifier CA,max First, the optimal load impedance value R of the control path power amplifier transistor is obtained by load pulling. opt，CA , the port impedance value is set to 50Ω by default, and the design of the control path power amplifier matching network is completed. After completing the design of the single-tube broadband control path power amplifier, the saturated fundamental current value I of the control path power amplifier can be obtained. CA,max Since the load impedance value Z of the control path power amplifier on the coupler plane CA Not affected by load modulation, ZCA Approximately equal to the characteristic impedance value Z of the hybrid coupler 0 The saturated output power of the control path power amplifier can be derived:

[0059]

[0060] Define α as the single-tube saturation power ratio between the control path power amplifier and the balance path power amplifier. The value of α is related to the output power back-off range of the load-modulated balanced power amplifier:

[0061]

[0062] Where P CA To control the saturated output power of the power amplifier, P BA is the saturated output power of a single-tube balanced power amplifier, Z BA is the impedance value of the coupler plane at the output end of the balanced power amplifier.

[0063] The output power back-off value OBO is:

[0064]

[0065] Assume Z BA Located on the real axis of the Smith chart, in order to achieve the expected 10-dB output back-off range, the value of α is 2 / 9. Substituting equation (3) into equation (2), Z can be calculated. BA is 26Ω.

[0066] The gate voltage of the balanced power amplifier is set to -5.8V and operates in Class C. The drain voltage is 28V.

[0067] The optimal load impedance R of the balanced power amplifier transistor is also obtained through load-pull simulation. opt，BA . Due to R opt，BA and Z BA The value of is known, so the matching network of the balanced power amplifier can be designed.

[0068] After completing the design of the single-tube balanced power amplifier, the saturation current value I of the balanced power amplifier at the coupler plane can be obtained. BA，max .

[0069] Furthermore, the saturated output power of the single-tube balanced power amplifier can be derived:

[0070]

[0071]

[0072] Where θ is the phase difference between the control path signal and the balance path signal.

[0073] And because the plane impedance value of the coupler at the output end of the balanced power amplifier can be expressed as:

[0074]

[0075] Z BA , Z 0 , I CA，max and I BA，max Substituting the value of into equation (6), the phase shift θ can be calculated 参考值 is a function of frequency. The in-band reference phase offset is calculated to be in the range of 124° to 179°.

[0076] Refer to the calculated θ 参考值 , comprehensively considering various performances such as broadband characteristics, backoff range and backoff efficiency, and optimizing the best phase offset value θ 实际值 , completing the overall design of broadband high back-off efficiency load modulation balanced power amplifier.

[0077] Figure 3 The comparison between the phase offset reference value and the actual phase offset value is shown. The values ​​of the two are very close in the entire frequency band, which verifies the rationality of the simplified method.

[0078] like Figure 4 As shown, the simulation results of the load impedance trajectory of the broadband high back-off efficiency load-modulated balanced power amplifier designed according to the method in the coupler plane show that the impedance value of the control path power amplifier CA is almost unaffected by the load modulation, and the real part of the load impedance values ​​of the balanced path power amplifiers BA1 and BA2 in the coupler plane is close to the 26Ω impedance circle when saturated, verifying the previous assumptions.

[0079] like Figure 5 As shown, the simulation results of the load impedance trajectory of the broadband high back-off efficiency load modulation balanced power amplifier designed according to the method in the current plane show that the impedance value of the control path power amplifier CA is almost unaffected by the load modulation, and the load impedance values ​​of the balanced path power amplifiers BA1 and BA2 in the coupler plane change along the real axis of the circular graph as the output power increases, and fit the optimal impedance trajectory.

[0080] like Figure 6 As shown, according to the design method, a 2.0GHz-2.8GHz load-modulated balanced power amplifier is designed and implemented. The simulation results show that the saturated drain efficiency is 48.5%-62.9%, the drain efficiency is 45%-52.1% at 6-dB power back-off, and the drain efficiency is 52.2%-66.3% at 10-dB power back-off.

[0081] like Figure 7 As shown, according to the design method, a 2.0GHz-2.8GHz load-modulated balanced power amplifier is designed and implemented. The measured results show that the saturated gain is 5-7.6dB and the saturated output power is 43.1-44.8dBm. The saturated drain efficiency is 47.7%-83.5%, the drain efficiency is 48.8%-65% at 6-dB power back-off, and the drain efficiency is 36.5%-45.7% at 10-dB power back-off.

[0082] Combining the above simulation results with the measured results, it is shown that the present invention is conducive to achieving a simplified design of a broadband high back-off efficiency load-modulated balanced power amplifier.

Claims

1. A load-modulated balanced power amplifier, characterized in that: The power amplifier comprises a hybrid coupler (1), a control path power amplifier circuit module (2), a phase shift module comprising a first phase shift module (31) and a second phase shift module (32), and a balanced path power amplifier circuit module (4); the hybrid coupler (1) divides a radio frequency input signal into two equal paths, namely a control path signal and a balanced path signal; the control path power amplifier circuit module (2) amplifies the control path signal from the hybrid coupler (1), and then outputs the amplified control path signal to the second phase shift module (32); the first phase shift module (31) and the second phase shift module (32) determine the phase shift between the control path signal and the balanced path signal, and reasonably set the phase difference between the two paths of signals to ensure negative The invention discloses a balanced power amplifier circuit module (4) for carrying out broadband characteristics and high back-off efficiency of a carrier modulated balanced power amplifier; the balanced power amplifier circuit module (4) comprises an input end hybrid coupler (41), a first balanced power amplifier (42), a second balanced power amplifier (43), and an output end hybrid coupler (44); the input end hybrid coupler (41) divides the balanced signal into two equal paths, and then injects them into the first balanced power amplifier (42) and the second balanced power amplifier (43) respectively; the output end hybrid coupler (44) receives the output signals of the first balanced power amplifier (42) and the second balanced power amplifier (43) for hybrid amplification; and finally combines the amplified balanced signal and the control signal injected from the second phase shift module (32) into a total output signal; The first phase shift module (31) and the second phase shift module (32) change the load impedance values ​​of the first balanced power amplifier (42) and the second balanced power amplifier (43) by affecting the phase shift between the control path signal and the balanced path signal, and achieve the purpose of fitting the optimal load impedance trajectory by providing a suitable phase difference within the frequency band, thereby achieving higher drain efficiency within a larger output power back-off range.

2. A load modulated balanced power amplifier according to claim 1, characterized in that: The hybrid coupler (1) equally divides a single input radio frequency signal into two signals with the same amplitude and a phase difference of 90 degrees, namely a control signal and a balanced signal.

3. The load modulated balanced power amplifier according to claim 1, characterized in that: The control path power amplifier circuit module (2) comprises a control path power amplifier input matching network (21), a control path power amplifier transistor (22), and a control path power amplifier output matching network (23); the base of the control path power amplifier transistor (22) is connected to the control path power amplifier input matching network (21), and the collector of the control path power amplifier transistor (22) is connected to the control path power amplifier output matching network (23).

4. A load modulated balanced power amplifier according to claim 3, characterized in that: The control path power amplifier transistor (22) selects a gallium nitride transistor with suitable output power as the control path power amplifier transistor as required, finds the optimal source impedance value and the optimal load impedance value through source pull simulation and load pull simulation, and the input and output port impedances of the control path power amplifier circuit module (2) are both 50Ω, thereby setting the control path power amplifier input matching network (21) and the control path power amplifier output matching network (23).

5. The load modulated balanced power amplifier according to claim 1, characterized in that: The first balanced power amplifier (42) comprises a first balanced power amplifier input matching network (421), a first balanced power amplifier transistor (422), and a first balanced power amplifier output matching network (423); the base of the first balanced power amplifier transistor (422) is connected to the output end of the first balanced power amplifier input matching network (421), and the collector of the first balanced power amplifier transistor (422) is connected to the first balanced power amplifier output matching network (423).

6. The load modulated balanced power amplifier according to claim 1, characterized in that: The second balanced power amplifier (43) comprises a second balanced power amplifier input matching network (431), a second balanced power amplifier transistor (432), and a second balanced power amplifier output matching network (433); the base of the second balanced power amplifier transistor (432) is connected to the output end of the second balanced power amplifier input matching network (431), and the collector of the second balanced power amplifier transistor (432) is connected to the second balanced power amplifier output matching network (433).

7. The load modulated balanced power amplifier according to claim 1, characterized in that: The input end hybrid coupler (41) and the output end hybrid coupler (44) in the balanced path power amplifier circuit module (4) both use 3-dB orthogonal couplers that respectively play the role of power distribution and power synthesis; the first balanced power amplifier (42) and the second balanced power amplifier (43) both use the same input matching and output matching networks to ensure that the phases of the two signals are consistent when they arrive at the output end hybrid coupler (44).

8. A method for designing a load modulated balanced power amplifier as claimed in claim 1, characterized in that: The method is based on a load-modulated balanced power amplifier. The method first derives the saturation current ratio and the load impedance value at the output hybrid coupler (44) port, then calculates the required reference phase difference, and finally optimizes the phase offset value of the control path power amplifier circuit module (2) to achieve widened bandwidth and high back-off efficiency, thereby completing the design of the load-modulated balanced power amplifier.

9. The method for designing a load-modulated balanced power amplifier according to claim 8, characterized in that: The design method comprises the following steps: S1: The optimal load impedance value Z of the control path power amplifier circuit module (2) is obtained through load pull simulation CA，opt The impedance value of the control path power amplifier circuit module (2) at the output end hybrid coupler (44) port is constant at 50Ω, and the saturation current I at the output end coupler plane is further obtained. CA，max ; S2: α is defined as the single-tube saturation power ratio between the control path power amplifier circuit module (2) and the balance path power amplifier circuit module (4). To achieve a 10-dB output power back-off range, the expected power ratio α is calculated to be 2 / 9. Then, the load impedance value Z of the balance path power amplifier circuit module (4) at the output hybrid coupler (44) port is derived according to the formula: BA ; S3: Obtain the optimal load impedance Z of the balanced power amplifier circuit module (4) through load-pull simulation BA,opt ; Due to Z BA,opt and Z BA The value of is known, so after independently completing the design of the balanced power amplifier circuit module (4), the saturation current value I at the output hybrid coupler (44) port is calculated. BA，max ; S4: Define Z0 as the characteristic impedance value of the hybrid coupler, θ as the phase difference between the control path signal and the balanced path signal, according to the formula Calculate the reference value of the phase difference θ 参考值 is a function of frequency; S5: With θ 参考值 As a reference for optimization, the overall circuit design of the load-modulated balanced power amplifier is completed, and the various indicators of broadband effect and back-off efficiency are comprehensively considered to obtain the actual optimal value θ of the simulated phase offset 实际值 , ultimately achieving excellent performance of broadband high back-off efficiency; S6: Verify the design and optimization method through physical processing and actual testing.

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