CN103475315B - Improve the device of linearity of radio-frequency power amplifier - Google Patents

Abstract

The present invention discloses a kind of device that improves linearity of radio-frequency power amplifier, comprising: main power amplifier, amplifies radiofrequency signal power; Radiofrequency signal Acquisition Circuit, gathers main power amplifier radio frequency input/output signal, and adjusts the power of radio frequency output signal; Analog predistortion device, preposition at main power amplifier, produce error signal, output pre-distorted signals, to the preliminary linearisation of main power amplifier; Error signal Circuit tuning, adjusts the error signal that analog predistortion device is exported, and ensures that the error signal of output is contrary with the amplitude equal phase of main path signal; Described analog predistortion device, main power amplifier, error signal Circuit tuning head and the tail order are connected, and form error cancellation loop, offset the distortion components of main path signal; Adaptation control circuit, utilizes radio frequency input/output signal, through Digital Signal Processing, exports control signal, further optimizes the linearisation effect of feedforward system. Simplify the complexity of conventional feed forward technical pattern, not only can obtain the high linearity, and improved by Self Adaptive Control the precision that system regulates.

Description

Device for Improving Linearity of Radio Frequency Power Amplifier

technical field

The invention relates to a radio frequency power amplifier linearization technology in wireless communication technology, in particular to a feedforward linearization technology of a radio frequency power amplifier, specifically a device for improving the linearity of a radio frequency power amplifier.

Background technique

With the development of wireless communication technology, more and more advanced communication standards have emerged, such as WCDMA, TD-SCDMA, WIMAX, LTE, etc., using multi-carrier technology with high spectrum utilization and complex digital modulation methods, such as 3G The downlink transmission of WCDMA standard of communication adopts QPSK modulation technology, and LTE adopts OFDM modulation technology. However, this method leads to a wide bandwidth and a high peak-to-average ratio of the baseband signal, which brings more serious challenges to the design of the power amplifier. In power amplifier design, efficiency and linearity are two key factors that must be considered. For signals with a peak-to-average ratio, the power amplifier needs to work in the power backoff area, which greatly reduces the efficiency of the power amplifier. When the power amplifier works in the saturation region, the efficiency is improved, but severe distortion occurs, mainly manifested as AM-AM/AM-PM distortion, which leads to signal spectrum expansion. At the same time, the increase of the signal bandwidth and the enhancement of the memory effect of the power amplifier have brought new challenges to the design and linearization of the power amplifier.

At present, there are four main methods of power amplifier linearization: back-off method, negative feedback method, pre-distortion method and feed-forward method. The fallback method is to make the power amplifier work in the fallback area, and its essence is to sacrifice the efficiency of the power amplifier to improve the linearity of the power amplifier. The back-off method is simple and easy to implement, but the efficiency of the power amplifier is significantly reduced, and the memory effect of the power amplifier cannot be avoided through power back-off, so the power back-off method must be used in combination with other linearization techniques. The negative feedback method is an earlier linearization method. Because it is difficult to ensure the stability of the system in the case of radio frequency, the radio frequency feedback is generally not directly used, but the modulation feedback technology is used to make the system work in a low frequency state. The commonly used modulation feedback techniques include envelope negative feedback, polar coordinate modulation negative feedback and Cartesian modulation negative feedback. The advantage of the negative feedback method is that the structure is simple, and the suppression effect of the intermodulation interference is better at the same time. However, the negative feedback method is a closed-loop system, and the gain of the amplifier must be large enough to achieve high gain and high distortion suppression. At the same time, the loop delay is the main limiting factor for negative feedback. In the high frequency band, the loop delay can reach several carrier cycles. , which limits the operating bandwidth of the linearizer. In addition, the negative feedback method also has stability problems. Therefore, the negative feedback method is suitable for single-carrier and single-channel situations, and is suitable for power amplifiers in mobile phones. The pre-distortion technology is to simulate the inverse characteristics of the power amplifier through the pre-distorter before the signal is amplified by the power amplifier, so that the entire system behaves linearly. Predistortion technology can be divided into analog predistortion and digital predistortion according to the different signals processed by the predistorter. Analog predistortion technology usually uses analog circuits to realize the predistorter, which has the advantages of simple implementation, low cost, unconditional stability, and easy high-frequency and broadband applications, but it has less suppression of spectrum regeneration components, and linearity improvement is easily affected by working conditions and the environment. , it is more difficult to cancel the high-order spectral components. There are two ways to realize the digital predistortion technology, one is realized through the parameter model of the nonlinear radio frequency power amplifier, and the other is realized through the look-up table. Digital predistortion has the advantages of simple implementation, easy signal processing, wide bandwidth, and good linearization effect. However, the modeling of digital predistortion requires at least 5 times the bandwidth of the baseband signal. The effect of predistortion is different from that of the power amplifier model. Direct relationship, and the hardware implementation of digital pre-distortion is relatively complicated. The basic idea of the feed-forward technology is to feed back the distorted signal samples generated by the main power amplifier to the output of the amplifier, so that the distorted signal at the output of the amplifier is greatly cancelled.

Figure 1 is a general simplified system block diagram of traditional feedforward technology. The traditional feedforward system contains two loops, which are the fundamental cancellation loop and the error cancellation loop. The RF input signal is divided into two channels through the power splitter, one channel passes through the main power amplifier MPA, coupler C1, attenuator A1, phase shifter P1, and coupler C2, and the other channel passes through the delay line L1 and coupler C2. The signal forms the fundamental cancellation loop. The function of the delay line is to ensure the delay alignment of the upper and lower signals of the fundamental cancellation loop. The signal output through the through end of coupler C1 reaches the power combiner through the delay line, and the signal output through the through end of coupler C2 reaches the power combiner through the attenuator A2, phase shifter P2, and auxiliary power amplifier DPA. These two signals constitute Error Cancellation Loop. Similarly, the delay line L2 of the error cancellation loop is used to ensure the delay alignment of the upper and lower signals. The fundamental wave cancellation loop is used to cancel the fundamental wave component output by the main power amplifier MPA to generate an error signal. The error cancellation loop is mainly to adjust the error signal to ensure that the error signal and the signal output by the main power amplifier MPA are equal in amplitude and opposite in phase, so that the error signal is fed into the main channel signal through the power combiner to cancel the distortion component of the main channel signal. It can be seen from Figure 1 that the implementation structure of traditional feedforward technology is complex, and it is difficult to adjust the signal. At the same time, with the change of working conditions and working environment, the amplitude and phase of the feedforward loop will change, and the linearization effect will change. Significantly decreased.

Contents of the invention

Aiming at the shortcomings of the traditional feedforward system, which is complex in structure and difficult to debug, and comprehensively considering the problems existing in the traditional feedforward system, the present invention proposes a new type of feedforward system. The system introduces an analog predistorter. On the one hand, it generates the error signal required by the error signal offset loop in the feedforward system, which simplifies the complexity of the error signal generated by the traditional feedforward technology. On the other hand, the analog predistorter itself has The effect of distortion can improve the linearity of the main power amplifier before the error cancellation loop. In order to maintain a good linearization effect, this technology introduces an adaptive control circuit, which can not only improve the linearization of the feedforward system, but also adjust the analog predistorter and the error signal adjustment circuit adaptively by collecting the RF input and output signals and processing the digital signal Effect, but also can improve the accuracy of the control feedforward system.

Technical scheme of the present invention is:

A device for improving the linearity of a radio frequency power amplifier, the device comprising:

- The main power amplifier, amplifying the power of the radio frequency signal;

- The RF signal acquisition circuit collects the RF input and output signals of the main power amplifier and adjusts the power of the RF output signal;

-Analog predistorter, in front of the main power amplifier, generates an error signal, outputs a predistortion signal, and initially linearizes the main power amplifier;

- The error signal adjustment circuit adjusts the error signal output by the analog predistorter to ensure that the output error signal is equal in amplitude and phase opposite to the main signal;

The analog predistorter, the main power amplifier, and the error signal adjustment circuit are sequentially connected end to end to form an error cancellation loop to offset the distortion component of the main channel signal;

- Adaptive control circuit, using radio frequency input and output signals, after digital signal processing, output control signals, further optimize the linearization effect of the feedforward system.

The radio frequency signal acquisition circuit at least includes a pre-coupler (100), a post-coupler (700) and an attenuator (800); a part of the radio frequency input signal and the radio frequency output signal are coupled as the input of the adaptive control circuit signal, the power of the coupled radio frequency output signal is adjusted by the attenuator (800); the input end of the pre-coupler (100) is connected to the radio frequency input signal, the through end is connected to the analog predistorter (200), and the coupling end is connected to the adaptive control circuit ( 900); the input end of the rear coupler (700) is connected to the output end of the power combiner (600), the through end outputs the radio frequency signal, and the coupling end is connected to the attenuator (800); the output end of the attenuator (800) is connected to the adaptive control circuit (900).

The analog predistorter (200) at least includes a power divider (201), an attenuator (202), a delay line (203), an error signal generation unit (204), a coupler (205), a vector modulator (206 ), the power combiner (207); inside the analog predistorter, one output signal of the power divider (201) reaches the power combiner (207) through the attenuator (202), the delay line (203), and the other signal passes through The error signal generation unit (204), the coupler (205), and the vector modulator (206) reach the power combiner (207); outside the analog predistortion, the input end of the power divider (201) is connected to the coupler (100) At the direct end, the output end of the power combiner (207) is connected to the input end of the main power amplifier (300). The analog predistorter (200) outputs two signals, and the error signal is output through the coupling end of the coupler (205), which is used as the input signal of the error signal adjustment circuit (500), and the predistortion signal output by the power combiner (207) , as the input signal of the main power amplifier (300); the analog predistorter (200) uses a vector modulator (206) instead of a traditional cascaded combination of an attenuator and a phase shifter to facilitate adaptive control.

The error signal adjustment circuit (500) at least includes an error amplifier (501), a vector modulator (502), and a secondary power amplifier (503); the input end of the error amplifier (501) is connected to the coupling end of the coupler (205), and the output Connect the RF input terminal of the vector modulator (502), the control terminal of the vector modulator (502) is connected to the output terminal of the adaptive control circuit (900), the output terminal is connected to the input terminal of the auxiliary power amplifier (503), and the auxiliary power amplifier (503 ) is connected to an input terminal of the power combiner (600); the error amplifier (501) is a linear amplifier, which linearly amplifies the small-signal error signal to facilitate the adjustment of the vector modulator (502); the vector modulator (502) according to the adapt to the control signal output by the control circuit, and adjust the amplitude and phase of the error signal; the auxiliary power amplifier (503) increases the power of the error signal to the required requirement.

The error cancellation loop includes at least an analog predistorter (200), a main power amplifier (300), a delay line (400), an error signal adjustment circuit (500), and a power combiner (600); in order to ensure that the upper and lower signals For delay alignment, a delay line (400) is designed, the input end of the delay line is connected to the output end of the main power amplifier, and the output end is connected to one input end of the power combiner (600); the other input end of the power combiner is connected to the error signal adjustment The output terminal of the unit; the error signal is fed into the main road signal through a power combiner (600), so as to cancel the distortion component of the main road signal.

The adaptive control circuit (900) at least includes a frequency down conversion (901), an anti-aliasing filter (902), an ADC (903), a DSP (904), a DAC (905), a reconstruction filter (906), Clock management (907); the two input terminals of the down-conversion (901) are connected to the output terminals of the radio frequency signal acquisition circuit, the output terminals are connected to the anti-aliasing filter (902), and the output terminals of the anti-aliasing filter (902) are connected to the ADC (903), the output of the ADC (903) is connected to the input of the DSP (904), the output of the DSP (904) is connected to the input of the DAC (905), and the output of the DAC (905) is connected to the reconstruction filter The input terminal of the filter (906), the output terminal of the reconstruction filter (906) is connected to the control terminal of the vector modulator (206) and the control terminal of the vector modulator (502), and the clock output of the clock management (907) is respectively connected to the ADC (903), clock pins of DSP (904), DAC (905); down-conversion (901) moves the frequency spectrum of the radio frequency signal to the intermediate frequency signal; the design cut-off frequency of the reconstruction stack filter (906) is DAC (905) Half of the sampling rate, complete the shaping of the output signal; DSP (904) is the core part of the adaptive control circuit, complete all signal processing, including digital down conversion, signal alignment, adaptive algorithm, channel equalization and IQ compensation; clock management (907) provides reference clocks for ADC (903), DSP (904), and DAC (905).

Beneficial effects of the present invention: There are two points of difference with the traditional feedforward linearization system, one is to use the analog predistorter to generate the error signal, which simplifies the complexity of the traditional feedforward technology to generate the error signal, and the analog predistorter itself has The function of linearization can further improve the linearity of the power amplifier. The second is to add an adaptive control circuit to adjust the performance of the system through an adaptive algorithm, and at the same time improve the accuracy of system adjustment.

Description of drawings

In order to illustrate the present invention and implement the system more clearly, the following introduces each module of the system through the accompanying drawings and detailed analysis.

Figure 1 Traditional feedforward linearization system

Figure 2 A device for improving the linearity of RF power amplifiers

Figure 3 Analog Predistorter

Figure 4 Error signal adjustment circuit

Figure 5 adaptive control circuit

Figure 6 DSP signal processing flow.

detailed description

In order to better understand and implement the present invention, the following will introduce the implementation of the entire system module through the accompanying drawings and detailed analysis, and specifically analyze the structure and function of each module.

Embodiment: Method and device for improving linearity of radio frequency power amplifier

Figure 2 is a device diagram for improving the linearity of a radio frequency power amplifier. The feedforward system is composed of the following parts: a radio frequency signal acquisition circuit, an analog predistorter, an error signal adjustment circuit, a main power amplifier, an error cancellation loop, and an adaptive control circuit. The radio frequency signal acquisition circuit collects the radio frequency input signal and the radio frequency output signal as the input signal of the adaptive control circuit. The analog predistorter, on the one hand, generates the error signal required by the error cancellation loop, which simplifies the complexity of the error signal generated by the traditional feedforward technology. On the other hand, it generates the predistortion signal, and first linearizes the main power amplifier. The error signal adjustment circuit adjusts the error signal so that its amplitude is equal to that of the main channel signal and its phase is opposite. The main power amplifier, which amplifies the power of the radio frequency signal, is also a component to be linearized. Error cancellation loop, the two signals output from the analog predistorter, one predistortion signal, through the main power amplifier and delay line to one input end of the power combiner, constitute the main circuit, and the other error signal reaches through the error signal adjustment circuit The other input terminal of the power combiner, and then the error signal is fed into the main road signal through the power combiner to cancel the distortion component in the main road signal. The adaptive control circuit is used for adaptively controlling the analog predistorter and the error signal adjustment circuit, so that the whole feedforward system works in a good state.

1 RF signal acquisition circuit

As shown in Fig. 2, the radio frequency signal acquisition circuit at least includes a pre-coupler (100), a post-coupler (700) and an attenuator (800). Coupling a part of the radio frequency input signal and the radio frequency output signal as the input signal of the adaptive control circuit. Considering that the power of the radio frequency output signal is greater than the power of the radio frequency input signal, the power of the coupled radio frequency output signal needs to be adjusted through an attenuator (800). The input end of the coupler (100) is connected to a radio frequency input signal, the through end is connected to an analog predistorter (200), and the coupling end is connected to an adaptive control circuit (900). The input end of the rear coupler (700) is connected to the output end of the power combiner (600), the through end outputs radio frequency signals, and the coupling end is connected to the attenuator (800). The output terminal of the attenuator is connected with an adaptive control circuit (900).

2 Analog Predistorters

As shown in Figure 3, the analog predistorter includes a power divider (201), an attenuator (202), a delay line (203), an error signal generation unit (204), a coupler (205), a vector modulator (206), and a power combiner (207). The input end of the power divider (201) is connected to the through end of the coupler (100), one output end is connected to the attenuator (202), the other output end is connected to the error signal generating unit (204), and the output end of the attenuator (202) The input end of the delay line (203) is connected, the output end of the delay line (203) is connected to an input end of the power combiner (207), the output end of the error signal generating unit (204) is connected to the coupler (205), and the coupler ( The straight-through end of 205) is connected to the radio frequency input end of the vector modulator (205), the coupling end is connected to the error signal adjustment circuit (500), the control end of the vector modulator (205) is connected to the output end of the adaptive control circuit (900), and the output The terminal is connected to an input terminal of the power combiner (207), and the output terminal of the power combiner (207) is connected to the input terminal of the main power amplifier (300). As shown in Figure 3, the radio frequency signal is divided into upper and lower signals through the power splitter (201), and the uplink signal reaches the power combiner (207) through the attenuator (202) and delay line (203), retaining the characteristics of the original input signal, called It is the main road. The main path passes through a delay line (203) to ensure delay alignment with the downlink signal. The downlink signal reaches the power combiner (207) through the error signal generating unit (204), the coupler (205), and the vector modulator (206). The analog predistorter outputs two signals, one is the error signal output by the coupling end of the coupler (205), which is used as the input signal of the error signal adjustment circuit (500), and the other is the output predistortion signal through the power combiner (206). , as the input signal of the main power amplifier (300).

In the design of the analog predistorter, a vector modulator is used to replace the traditional cascaded combination of a variable attenuator and a phase shifter. There is a defect in the cascaded form of the traditional attenuator and phase shifter. When the control signal of the attenuator and phase shifter changes, it will bring about a change in group delay, which seriously affects the performance of the predistortion. At the same time, the adjustment of the attenuator and the phase shifter will affect each other, and it is difficult to precisely control the pre-distortion. The vector modulator can not only independently control the amplitude and phase of the signal, but also accept the control signal of the adaptive control circuit to adaptively control the performance of the analog predistorter.

3 Error signal adjustment circuit

As shown in Fig. 3, the error signal adjustment circuit includes an error amplifier (501), a vector modulator (501) and a sub power amplifier (503). The input end of the error amplifier (501) is connected to the coupling end of the coupler (205), the output end is connected to the radio frequency input end of the vector modulator (502), and the control end of the vector modulator (502) is connected to the output of the adaptive control circuit (900). port, the output end is connected to the input end of the auxiliary power amplifier (503), and the output end of the auxiliary power amplifier (503) is connected to an input end of the power combiner (600). The error amplifier (501) is a linear amplifier, which linearly amplifies the small-signal error signal to facilitate the adjustment of the vector modulator (502). The vector modulator (502) adjusts the amplitude and phase of the error signal according to the control signal of the adaptive control circuit (900). The secondary amplifier boosts the power of the error signal to the required level. The function of the error signal adjustment module is to adjust the error signal to ensure that the amplitude of the error signal is equal to that of the main signal of the error cancellation loop and the phase is opposite.

Here, the vector modulator is also used instead of the traditional cascaded combination of variable attenuator and phase shifter, which is convenient for receiving the control signal of the adaptive control circuit and adaptively adjusting the error signal.

4 main amplifier

The input end of the main power amplifier (300) is connected to the radio frequency output of the analog predistorter (200), and the output end is connected to the input end of the delay line (400). The main power amplifier (300) is the main component of the feedforward system and also the component to be linearized. In order to improve the efficiency of the power amplifier, the main power amplifier (300) works in the saturation region, which inevitably produces distortion components.

5 Error Cancellation Loop

The error cancellation loop is composed of an analog predistorter (200), a main power amplifier (300), a delay line (400), an error signal adjustment circuit (500), and a power combiner (600). The output end of the power combiner (207) in the analog predistorter (200) is connected to the input end of the main power amplifier (300), and the coupling end of the coupler (205) in the analog predistorter is connected to the error signal adjustment circuit (500). The input terminal, the output terminal of the main power amplifier (300) is connected to the input terminal of the delay line (400), the output terminal of the delay line (400) is connected to an input terminal of the power combiner (600), and the output terminal of the error adjustment circuit (500) The other input end of the power combiner is connected, and the output end of the power combiner (600) is connected with the input end of the coupler (700).

The predistortion signal output from the analog predistorter (200) reaches an input terminal of the power combiner (600) through the main power amplifier (300) and the delay line (400), forming a main circuit. The error signal output from the analog predistorter (200) passes through the error signal adjustment circuit (500), and is fed into the main channel signal through the power combiner (600), so as to cancel the distortion component of the main channel signal. In order to ensure the delay alignment of the upper and lower signals, a delay line (400) is designed.

6 adaptive control circuit

Feedforward amplifiers are sensitive to amplitude, phase, and delay in suppressing distorted signals. The power gain of a power amplifier varies with ambient temperature and carrier frequency. Moreover, the feedforward system requires that the amplitude, phase, and delay of the two signals be completely matched to completely cancel the distortion component in the main signal, and the system is highly sensitive. Therefore, it is necessary to carry out adaptive control on the feedforward system and correct the system parameters in real time to ensure that the output signal of the power amplifier has good linearity.

As shown in Figure 5, the adaptive control circuit (900), including frequency down conversion (901), anti-aliasing filter (902), ADC (903), DSP (904), DAC (905), reconstruction filter (906) , Clock Management (907). The two input ends of the down-conversion (901) are connected to the output end of the radio frequency signal acquisition circuit, the output end is connected to the anti-aliasing filter (902), and the output end of the anti-aliasing filter (902) is connected to the input end of the ADC (903) , the output of the ADC (903) is connected to the input of the DSP (904), the output of the DSP (904) is connected to the input of the DAC (905), and the output of the DAC (905) is connected to the input of the reconstruction filter (906) terminal, the output terminal of the reconstruction filter (906) is connected to the control terminal of the vector modulator (205) and the control terminal of the vector modulator (502), and the clock output of the clock management (907) is respectively connected to the ADC (903), DSP ( 904), clock pin of DAC (905).

Frequency down conversion (901) moves the frequency spectrum of the radio frequency signal to the intermediate frequency signal. After the radio frequency signal is down-converted, many other frequency components will appear. On the one hand, useless frequency components are filtered out; The cut-off frequency of the anti-aliasing filter (902) should meet the requirements of low-pass sampling, and at the same time, the flatness of gain in the band should meet certain requirements, and the phase should meet the linear phase. The device selection of ADC (903) and DAC (905) needs to comprehensively consider bit width, sampling rate and cost. The center frequency of the intermediate frequency signal of the feedforward system is generally around 30MHz, and the sampling rate should be increased as much as possible to meet the requirements of low-pass sampling. Here, the sampling rate can be selected to be 5-7 times the intermediate frequency, that is, ADC (903) and DAC (905 ) with a sampling rate of at least 150MSPS. Considering the operation precision, quantization noise and cost, a device with a bit width of at least 12 bits can be selected here. In order to facilitate the control of two-way signals and satisfy data synchronization at the same time, a dual-channel device is selected. The design of the reconstruction stack filter (906) also first needs to meet the requirements of low-pass sampling, and the cutoff frequency is generally designed to be half of the sampling rate of the DAC (905). The control signal output by the reconstruction filter (906) respectively controls the analog predistorter (200) and the error signal adjustment unit.

DSP (904) is the core part of the adaptive control circuit and completes all signal processing. DSP first converts the intermediate frequency signal sampled by the ADC into a digital baseband signal through digital down-conversion. Since the input data and the output data are not synchronized, it is necessary to align the data delay by correlation and other methods. After the aligned input and output data, according to the adaptive algorithm, the signal processing is completed and the control signal is output. Because the vector modulator is not ideal in practice, the IQ data is not 90° quadrature, so it is necessary to compensate the IQ imbalance in the DSP. Since the signal will pass through DAC, reconstruction filter and some analog circuits, linear distortion will inevitably occur, so channel equalization is required for the output channel. Through analysis, the specific signal processing flow of DSP can be obtained as shown in Figure 6.

The above-mentioned embodiments specifically illustrate the device for improving the linearity of the RF power amplifier, and analyze the concept and characteristics of the system in detail. For those of ordinary skill in the technical field to which the present invention belongs, various modifications and changes can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A device for improving the linearity of a radio frequency power amplifier, the device comprising: - The main power amplifier, amplifying the power of the radio frequency signal; - The RF signal acquisition circuit collects the RF input and output signals of the main power amplifier and adjusts the power of the RF output signal; -Analog predistorter, in front of the main power amplifier, generates an error signal, outputs a predistortion signal, and initially linearizes the main power amplifier; - The error signal adjustment circuit adjusts the error signal output by the analog predistorter to ensure that the output error signal is equal in amplitude and phase opposite to the main signal; The analog predistorter, the main power amplifier, and the error signal adjustment circuit are sequentially connected end to end to form an error cancellation loop to offset the distortion component of the main channel signal; - Adaptive control circuit, using radio frequency input and output signals, after digital signal processing, output control signals, further optimize the linearization effect of the feedforward system. 2. The device for improving the linearity of a radio frequency power amplifier according to claim 1, wherein the radio frequency signal acquisition circuit at least includes a pre-coupler (100), a post-coupler (700) and an attenuator (800); couple a part of the radio frequency input signal and the radio frequency output signal as the input signal of the adaptive control circuit, and adjust the power of the coupled radio frequency output signal through the attenuator (800); the input end of the pre-coupler (100) is connected to the radio frequency Input signal, the through end is connected to the analog predistorter (200), the coupling end is connected to the adaptive control circuit (900); the input end of the rear coupler (700) is connected to the output end of the power combiner (600), and the through end outputs radio frequency signal, the coupling end is connected to an attenuator (800); the output end of the attenuator (800) is connected to an adaptive control circuit (900). 3. The device for improving the linearity of a radio frequency power amplifier according to claim 1, wherein the analog predistorter (200) at least includes a power splitter (201), an attenuator (202), a delay line ( 203), an error signal generation unit (204), a coupler (205), a vector modulator (206), and a power combiner (207); inside the analog predistorter, one output signal of the power divider (201) is attenuated The device (202), the delay line (203) reach the power combiner (207), and the other signal reaches the power combiner (207) through the error signal generating unit (204), the coupler (205), and the vector modulator (206); Outside the analog predistortion, the input end of the power divider (201) is connected to the through end of the coupler (100), and the output end of the power combiner (207) is connected to the input end of the main power amplifier (300); The analog predistorter (200) outputs two signals, and the error signal is output through the coupling end of the coupler (205), which is used as the input signal of the error signal adjustment circuit (500), and the predistortion signal output by the power combiner (207) , as the input signal of the main power amplifier (300); the analog predistorter (200) uses a vector modulator (206) instead of a traditional cascaded combination of an attenuator and a phase shifter to facilitate adaptive control. 4. The device for improving the linearity of a radio frequency power amplifier according to claim 1, characterized in that the error signal adjustment circuit (500) at least includes an error amplifier (501), a vector modulator (502), and a secondary power amplifier ( 503); the input end of the error amplifier (501) is connected to the coupling end of the coupler (205), the output end is connected to the radio frequency input end of the vector modulator (502), and the control end of the vector modulator (502) is connected to the adaptive control circuit ( 900), the output end is connected to the input end of the sub-amplifier (503), and the output end of the sub-amplifier (503) is connected to an input end of the power combiner (600); the error amplifier (501) is a linear amplifier, and the small signal The error signal is linearly amplified to facilitate the adjustment of the vector modulator (502); the vector modulator (502) adjusts the amplitude and phase of the error signal according to the control signal output by the adaptive control circuit; the auxiliary power amplifier (503) increases the power of the error signal to the required requirements. 5. The device for improving the linearity of a radio frequency power amplifier according to claim 1, characterized in that the error cancellation loop at least includes an analog predistorter (200), a main power amplifier (300), and a delay line (400) , error signal adjustment circuit (500), power combiner (600); in order to ensure the delay alignment of the upper and lower signals, a delay line (400) is designed, the input end of the delay line is connected to the output end of the main power amplifier, and the output end is connected to the power amplifier One input end of the combiner (600); the other input end of the combiner is connected to the output end of the error signal adjustment unit; the error signal is fed into the main channel signal through the combiner (600) to cancel the distortion component of the main channel signal . 6. The device for improving the linearity of a radio frequency power amplifier according to claim 1, characterized in that the adaptive control circuit (900) at least includes a frequency down conversion (901), an anti-aliasing filter (902), and an ADC (903), DSP (904), DAC (905), reconstruction filter (906), clock management (907); the two input ends of the down conversion (901) are connected to the output end of the radio frequency signal acquisition circuit, and the output end is connected to The anti-aliasing filter (902), the output end of the anti-aliasing filter (902) is connected to the input end of the ADC (903), the output end of the ADC (903) is connected to the input end of the DSP (904), and the DSP (904) The output terminal is connected to the input terminal of the DAC (905), the output terminal of the DAC (905) is connected to the input terminal of the reconstruction filter (906), and the output terminal of the reconstruction filter (906) is connected to the control terminal of the vector modulator (206). and the control terminal of the vector modulator (502), the clock output of the clock management (907) is respectively connected to the clock pins of the ADC (903), DSP (904), and DAC (905); the down-conversion (901) converts the frequency spectrum of the radio frequency signal Move to the intermediate frequency signal; the design cut-off frequency of the reconstruction stack filter (906) is half of the sampling rate of the DAC (905) to complete the shaping of the output signal; the DSP (904) is the core part of the adaptive control circuit to complete all the signal Processing, including digital down-conversion, signal alignment, adaptive algorithm, channel equalization and IQ compensation; clock management (907) provides reference clocks for ADC (903), DSP (904), and DAC (905).