Research On Digital Pre-distortion Linearization Technology Of Short Wave Power Amplifier

With the rapid development of wireless communication, short wave communication is no longer a simple transmission of voice signals, and has been extended to the business scope of digital communication. The great expansion of application range makes short wave communication channel is very crowded, so how to transmit large amounts of voice, images,video and other information in the limited channel bandwidth is very important. With the application of the higher modulation non-constant envelope signals and broadband signal that is superimposed by multi-channel signal, the transmission efficiency of short wave communication significantly increases, at the same time linearity is greatly reduced. Therefore,improving the PA linearity is most critical in the condition of ensuring efficient transmission.This paper mainly study short-wave power amplifier(PA) digital predistortion linearization technology. The article firstly analyzes the characteristics and generating methods of nonconstant envelope single side band modulation signal which used in communication, thus put forwards the necessity of short wave PA linearization, and elaborates shortwave PA nonlinear characteristics by PA indicators and nonlinear indicators, then describes several digital predistortion methods to establish amplifier behavioral modelsThis paper then puts forward the structure design of the adaptive short wave power amplifier digital pre-distortion system, and introduces the key technology of digital predistortion in detail, such as delay estimation and adjustment, training data extraction and model parameters extraction. The paper proposes the coarse delay estimation algorithm of the margin difference superposition and the fine delay estimation of the partial interpolation in the process of eliminating the loop delay to achieve a low complexity and high accuracy delay estimation,and analyzes the model parameters extraction algorithm of the look-up tables, memory polynomial and augmented Hammerstein, then improves the traditional look-up table algorithm according to short wave PA characteristic, and puts forward the fitting method of segmented,non-uniform take points which fits the characteristic curve of short wave amplifier exactly.This article realizes shortwave PA adaptive digital pre-distortion system on the DSP and FPGA united platform based on the improved look-up table mode. The function of DSP part is to complete the digital pre-distortion algorithm design,including the linearity monitoring of PA output, delay estimation and adjustment, training data extraction and parameter extraction andso on.The function of FPGA part is to complete the programming of the predistorter module, up and down conversion module, data receiver transmitter module and so on.Finally,the article carries on experimental verification for this technology and adaptive digital pre-distortion platform by combining AB class short wave PA.With 24 KHz wide band multi-carrier signal as an incentive and 125 W power output of short wave PA, the adjacent channel power ratio(ACPR) of output signal improves more than 20 dB.