阅读说明：本技术 一种非线性功放的高性能数字预失真方法 (High-performance digital predistortion method of nonlinear power amplifier ) 是由 雷易鸣 郝亮 杜一鹏 金野 于 2019-01-08 设计创作，主要内容包括：本发明公布一种非线性功放的高性能数字预失真方法,包括：通过对功率放大器进行建模,采集功率放大器的输入信号,计算功放模型输出信号；进行归一化；定义功放模型输出信号放缩比；计算归一化误差向量；还原为输出端误差向量；计算消除误差向量后的功放模型输出信号,并进行限幅操作,得到高性能预失真功放模型输出信号；对功放模型进行逆运算,求解高性能预失真功放模型输出信号所对应的高性能预失真功放模型输入信号,再输入非线性功放,即完成非线性功放的数字预失真。本发明能够实现抑制功放输出信号非线性失真的高性能数字预失真,具有优异的线性化性能。(The invention discloses a high-performance digital predistortion method of a nonlinear power amplifier, which comprises the following steps: the method comprises the steps of modeling a power amplifier, collecting an input signal of the power amplifier, and calculating an output signal of a power amplifier model; carrying out normalization; defining the output signal scaling ratio of a power amplifier model; calculating a normalized error vector; reducing the error vector into an output end error vector; calculating the power amplifier model output signal after the error vector is eliminated, and carrying out amplitude limiting operation to obtain a high-performance pre-distortion power amplifier model output signal; and performing inverse operation on the power amplifier model, solving a high-performance pre-distortion power amplifier model input signal corresponding to the high-performance pre-distortion power amplifier model output signal, and inputting the high-performance pre-distortion power amplifier model input signal into the nonlinear power amplifier, namely completing the digital pre-distortion of the nonlinear power amplifier. The invention can realize high-performance digital predistortion for inhibiting the nonlinear distortion of the output signal of the power amplifier and has excellent linearization performance.)

1. A high-performance digital predistortion method of a nonlinear power amplifier is characterized by comprising the following steps:

1) modeling the power amplifier to obtain a power amplifier model;

2) collecting input signal S of power amplifier_inCalculating the input signal S_inCorresponding power amplifier model output signal

3) To power amplifier input signal S_inAnd the output signal of the power amplifier modelNormalizing to obtain normalized power amplifier input signalAnd normalizing the output signal of the power amplifier modelIn addition, the output signal scaling of the power amplifier model is defined as follows:

4) calculating a normalized error vectorNormalized error vectorRepresenting the error between the input and output signals of the power amplifier model;

5) will normalize the error vectorReverting to the output end error vector e_out；

6) Power amplifier model output signal after error vector is eliminated through calculationThen carrying out amplitude limiting operation to obtain expected predistortion output signalThe specific operation is as follows:

61) removing an error vector in the output signal of the power amplifier model to obtain the output signal of the power amplifier model after the error vector is removed; the specific operation is as follows:

wherein the content of the first and second substances,the output signal of the power amplifier model after the error vector is eliminated is expressed as the output signal of the power amplifier modelAnd the output end error vector e_outThe vector sum of (1);

62) according to the power amplifier model in the step 1), calculating the maximum output amplitude of the power amplifier, and recording as S_sa；

63) To pairCarrying out amplitude limiting operation;

if it isGetTo pairCarrying out amplitude limiting processing; if it isThen it is not rightCarrying out amplitude limiting processing;

64) by pairsPower amplifier model output signal with error vector eliminatedTo obtain the desired pre-distorted output signalExpressed as:

wherein the content of the first and second substances,representing a vectorThe phase of (d);

7) inverse operation is carried out on the power amplifier model to solve the expected predistortion output signalCorresponding PA high-performance digital predistortion input signalThe signal is a pre-distorted output signal DPD_outAnd inputting the signal into a nonlinear power amplifier to finish digital predistortion.

2. The method for high-performance digital predistortion of a nonlinear power amplifier according to claim 1, wherein in the step 3), the specific operation method for normalization is as follows:

normalized power amplifier input signal

Normalized power amplifier model output signal

3. The method for high performance digital predistortion of nonlinear power amplifier in accordance with claim 1, wherein in step 4), the error vector is normalizedThe vector difference between the normalized power amplifier input signal and the normalized power amplifier model output signal is expressed as formula 4:

wherein the content of the first and second substances,normalizing the power amplifier input signal;and outputting signals for the normalized power amplifier model.

4. The method for high performance digital predistortion of nonlinear power amplifier in accordance with claim 1, wherein in step 5), the error vector is normalizedReverting to the output end error vector e_outSpecifically, it is represented by formula 5:

wherein α is the power amplifier model output signal scaling.

5. The method of claim 1, wherein step 7) is specifically operable to:

inverting the power amplifier model obtained in the step 1) to obtain a power amplifier output-input signal relational expression;

then the expected predistortion output signal obtained in the step 6) is obtainedSolving PA high-performance digital predistortion input signal in inverse of power amplifier modelI.e. the predistortion output signal DPD_out；

DPD_outAnd inputting the nonlinear power amplifier to finish high-performance digital predistortion.

Technical Field

The invention belongs to the technical field of wireless communication, relates to a nonlinear power amplifier system optimization and digital predistortion technology, and particularly relates to a high-performance digital predistortion method for a nonlinear power amplifier.

Background

In modern communication market, there is an increasing demand for communication systems with high carrier frequency and wide channel bandwidth, and such communication systems widely use signals with high peak-to-average power ratio and wide signal bandwidth to obtain higher spectral efficiency, and also bring more complicated modulation and demodulation protocols. In the upcoming 5G scenario, it is anticipated that non-linear distortion of the power amplifier will still be a major distortion source for the communication system.

Accordingly, a Digital Predistortion (DPD) technique is developed, in which a predistortion element is cascaded with a power amplifier to generate a signal that can cancel out the nonlinear distortion of the power amplifier, and the two nonlinear distortions are combined to realize a highly linear and distortion-free communication system.

However, it is very complicated to implement the digital predistortion technique, and the linearization performance of the conventional digital predistortion gradually deteriorates under the condition that the carrier frequency is higher and higher. If the prior performance index requirement is met, the power amplifier output signal will suffer from serious degradation, and this method may not improve the performance of the communication system, or even degrade the performance. Moreover, the main development direction of the current mainstream DPD technology is to perform more precise modeling for the behavior of the power amplifier. These methods put high demands on the calculation amount of the digital predistortion equipment, and are not beneficial to the miniaturization of the equipment. Therefore, it is necessary to find a simple and efficient digital predistortion method with good linearity performance.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a high-performance digital predistortion method of a nonlinear power amplifier, which has the advantage of good linearization performance.

The invention aims to provide a novel high-performance digital predistortion method for a nonlinear power amplifier. The method provides a high-performance digital predistortion method for inhibiting the nonlinear distortion of the output signal of the power amplifier and provides a realization process thereof by modeling the power amplifier and analyzing the error vector and the power amplifier characteristic of the output signal of the power amplifier model. Compared with the current mainstream digital predistortion method, the method has excellent linearization performance and is a high-performance digital predistortion method.

The technical scheme provided by the invention is as follows:

a high-performance digital predistortion method of a nonlinear power amplifier comprises the following steps:

1) modeling a Power Amplifier (PA) to obtain a Power Amplifier model;

2) collecting input signal S of power amplifier_inCalculating the input signal S_inCorresponding power amplifier model output signal

3) To power amplifier input signal S_inAnd the output signal of the power amplifier modelNormalizing to obtain normalized power amplifier input signalAnd normalizing the output signal of the power amplifier model

4) Calculating a normalized error vector

5) Will normalize the error vectorReverting to the output end error vector e_out；

6) Power amplifier model output signal after error vector is eliminated through calculationThen carrying out amplitude limiting operation to obtain expected predistortion output signalCalculating an expected output signal of the PA after high-performance predistortion;

7) inverse operation is carried out on the power amplifier model, and PA expected predistortion output signals are solvedCorresponding PA high-performance digital predistortion input signalI.e. the predistortion output signal DPD_outAnd inputting the nonlinear power amplifier, thereby finishing the high-performance digital predistortion for restraining the nonlinear distortion of the output signal of the power amplifier.

Preferably, in step 3), the power amplifier is input with a signal S_inAnd the output signal of the power amplifier modelNormalizing to obtain normalized power amplifier input signalAnd normalizing the output signal of the power amplifier modelThe specific operation method comprises the following steps:

calculating a normalized power amplifier input signal:

calculating an output signal of the normalized power amplifier model:

in addition, the output signal scaling of the power amplifier model is defined as follows:

preferably, in step 4), a normalized error vector is calculatedThe specific operation is as follows:

normalized error vectorRepresenting the error vector between the input signal and the output signal of the power amplifier model for the vector difference between the input signal and the output signal of the normalized power amplifier model, and representing as follows:

preferably, in step 5), the error vector is normalizedReverting to the output end error vector e_outThe method specifically comprises the following steps:

normalizing the error vector obtained in the step 4)Reducing the error vector into an output end error vector, wherein the reduction process comprises the following steps:

wherein α is the power amplifier model output signal scaling ratio obtained in step 3).

Preferably, in step 6), the model output signal after the error vector is eliminated is calculatedThen carrying out amplitude limiting operation to obtain expected predistortion output signalThe specific operation is as follows:

61) removing an error vector in the output signal of the power amplifier model to obtain the output signal of the power amplifier model after the error vector is removed; the specific operation is as follows:

wherein the content of the first and second substances,outputting signals for the power amplifier model after eliminating the error vectorAnd the output end error vector e_outThe vector sum of (1).

62) According to the power amplifier model obtained in the step 1), calculating the maximum output amplitude of the power amplifier, and recording as S_sa。

63) To pairCarrying out amplitude limiting operation;

if it isWherein S_saFor the maximum output amplitude of the power amplifier, the maximum output amplitude is obtainedTo pairCarrying out amplitude limiting processing; if it isThen it is not rightAnd carrying out amplitude limiting processing.

64) Outputting signals through the power amplifier model after eliminating error vectorsPerforming a clipping operation to obtain a desired pre-distorted output signalCan be expressed as:

wherein the content of the first and second substances,representing a vectorThe phase of (c).

Preferably, in step 7), inverse operation is performed on the power amplifier model to solve the expected predistortion output signalCorresponding PA high-performance digital predistortion input signalThe signal is a pre-distorted output signal DPD_outInputting a nonlinear power amplifier to finish predistortion, and specifically operating as follows:

inverting the power amplifier model obtained in the step 1) to obtain a power amplifier output-input signal relational expression, and then carrying out the expected predistortion output signal obtained in the step 6)Solving PA high-performance digital predistortion input signal in inverse of power amplifier model I.e. the predistortion output signal DPD_outDPD_outAnd inputting a nonlinear power amplifier to finish predistortion.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a high-efficiency digital predistortion method of a nonlinear power amplifier. According to the method, the error vector and the power amplifier characteristic of the output signal of the power amplifier model are analyzed according to the input signal and the output signal of the power amplifier model, the normalized error vector of the power amplifier is solved, and then the error vector is removed from the output of the power amplifier model, so that high-efficiency digital predistortion is realized, and the method has profound significance for equipment miniaturization production. In addition, compared with the defects of non-ideal linearization effect and the like of the traditional digital predistortion technology, the method is simple to implement and has excellent linearization effect.

Drawings

FIG. 1 is a block diagram of an implementation structure of the high performance digital predistortion method of a nonlinear power amplifier according to the present invention;

fig. 2 is an AM-AM curve of an L DMOS power amplifier and AM-AM curves of two mainstream digital predistortion methods employed in an implementation of the present invention;

the two mainstream digital predistortion methods are a pure linear digital predistortion method and a hard amplitude limiting digital predistortion method respectively.

FIG. 3 is a graph of normalized power spectral density of an input signal versus a purely linear digital predistortion output signal in accordance with an embodiment of the present invention;

wherein the upper graph is the normalized power spectral density of the input signal of the power amplifier; the lower graph is the normalized power spectral density of the power amplifier output signal using the pure linear digital predistortion method.

FIG. 4 is a graph of normalized power spectral density of an output signal using a hard-clipping digital predistortion method in accordance with an embodiment of the present invention compared to a high performance digital predistortion method in accordance with the present invention;

wherein, the upper graph is the normalized power spectral density of the output signal of the power amplifier adopting the hard-clipping digital predistortion method; the lower graph is the normalized power spectral density of the power amplifier output signal using the high performance digital predistortion method of the present invention.

Detailed Description

The invention will be further described by way of examples, without in any way limiting the scope of the invention, with reference to the accompanying drawings.

The invention provides a high-performance digital predistortion method of a nonlinear power amplifier. An efficient method for restraining nonlinear distortion of a power amplifier is provided by modeling the power amplifier and normalizing an input signal and an output signal of a power amplifier model to solve an error vector.

In general, in the embodiment, the input power and the output power of the power amplifier are all based on the 1dB output back-off point of the lateral diffusion metal oxide semiconductor (L DMOS) power amplifier, and correspondingly, the AM-AM curves of the three digital predistortion methods in the figure 2 are normalized according to the reference point.