A Power Amplifier Piecewise Linearization Digital Predistortion Method And Verification

In the communication system,the RF power amplifier is used to amplify the power of the transmitted signal and expand the communication distance.As the core component of the front end of the wireless communication system,the performance of the RF power amplifier directly determines the quality of the transmitted signal.However,in the highefficiency operating state,the inherent nonlinear characteristics of the amplifier will cause the transmitted signal to be amplified while generating nonlinear distortion,deteriorate the communication quality,and cause problems such as out-of-band spectrum spreading.In order to enable the power amplifier to transmit efficiently and reduce the adverse effects caused by its nonlinear distortion,the power amplifier needs to be linearized.In this essay,a piecewise linearized nonlinear fitting model is used to achieve a digital predistortion method and experimental verification.Mainly use the mathematical software MATLAB as the predistortion parameter calculation platform to realize the software simulation of power amplifier nonlinear modeling and correction,and design and implement a programmable on-chip digital predistortion system on the FPGA(Field Programmable Gate Array)platform.The main research contents of this article are as follows:First,the nonlinear distortion characteristics of the RF power amplifier and several common behavior models are analyzed.The relevant knowledge of digital predistortion technology is summarized,analyzed,compared,and finalized from the principles,key technologies,system implementation methods,evaluation indicators,etc.And finally determine the implementation form of MATLAB and FPGA in this essay.Second,after analyzing the program requirements,overall digital pre-distortion solution,system model and pre-distortion process of this essay are given.The overall implementation block diagram is divided into two parts,MATLAB and FPGA.The principle and specific implementation methods of each functional module in the block diagram are introduced in the order of hardware connection.The piecewise linear expression formula of the nonlinear system is derived,and the parameters required by the PWL-LUT predistorter model are introduced.Comprehensive consideration of parameter calculation speed,FPGA platform resource consumption and predistortion effect,after theoretical derivation,a parameter calculation method that is easy to implement in engineering is given,that is,approximate real-time feedback data is replaced by approximate iteration.Third,build an FPGA engineering link to test and analyze the power amplifier behavior model,the correctness of the predistorter parameters,and the overall design scheme of digital predistortion based on piecewise linearization.By comparison with the verified memory polynomial predistorter model,it can be seen that the normalized mean square error of the input and output of the system after predistortion processing in this scheme can be improved by 8.5 dB,10 dB improvement in out-of-band spectral leakage suppression.This essay completes the design and experimental verification of the digital predistortion technology scheme based on piecewise linearization.The results show that the digital predistortion method based on piecewise linearization can effectively suppress the nonlinear distortion of RF power amplifiers by up to 10 dB.It shows that this method has certain guiding value in power amplifier linearization related projects.