Research On Linearization Technology Of Frequency Hopping Power Amplifier Based On Orthogonal Chebyshev Polynomial

Frequency hopping technology is widely used in military and civil communications due to its strong anti-jamming ability and easy networking.As the core component of the frequency hopping communication system,the linearization level of the power amplifier affects the transmission efficiency,energy consumption and communication quality of the entire system.Modern frequency hopping communication systems use high-order modulation to ensure high spectrum utilization,which,however,causes serious nonlinear distortion introduced by the power amplifier and hence,reduces communication quality Current research on power amplifier linearization mostly focuses on the digital predistortion where the carrier frequency is fixed.Against this background,this thesis designs a technical solution for power amplifier linearization with frequency hopping,and implements the project based on FPGA.The research contents mainly include:Firstly,determine the digital predistorter model in the frequency hopping communication scenario.The condition number of the data matrix in the memory polynomial model increases rapidly as the increase of the model order,which leads to the problem of instability of the digital predistortion.Therefore,an orthogonal Chebyshev polynomial is used to construct the predistorter to ensure the stability of the algorithm.At the same time,the data of the measured power amplifier are collected and its nonlinear characteristics are analyzed.On this basis,the model dimensions of the power amplifier are designed,and the performance is compared with the memory polynomial model.Secondly,the technical linearization scheme of frequency hopping power amplifier is designed.Considering that the characteristics are similar for adjacent frequency points of the power amplifier,the segmentation method in which the adjacent frequency points share the same set of correction coefficients is adopted to achieve a tradeoff between the performance and complexity of the system.Another question is that the hopping frequencies leads to the instability of coefficients solution.In order to reduce the probability of an ill-conditioned matrix when solving the correction coefficients,the Tikhonov regularization algorithm is proposed for the calculation of the correction coefficients.Add the fitted power amplifier model to the link for simulation to verify the feasibility and performance of the scheme.Thirdly,the implementation and engineering verification of power amplifier linearization with frequency hopping is verified based on FPGA.In the implementation process,the development of Tikhonov regularization algorithm is completed using highlevel synthesis tools to improve development efficiency.Designs for key modules are optimized,and resource consumption is evaluated.The experimental results verify the feasibility of the power amplifier linearization with frequency hopping and the applicability of the correction coefficient segmentation.For 10 MHz broadband signals using QPSK/16 QAM modulation,frequency hopping power amplifier linearization technology can reduce its ACPR index from-33 d Bc to-46 d Bc.This thesis studies the power amplifier linearization scheme in frequency hopping scenarios,including the power amplifier and predistorter modeling method based on orthogonal chebyshev polynomials and the extraction algorithm of correction coefficients.The research results can be applied to frequency hopping communication systems such as vehicle-mounted and piggy-back frequency hopping radios,satellite communications,etc.,to improve the linearity of power amplifiers and reduce out-of-band spectrum proliferation.