功率放大器非线性对Chirp信号的影响 及预补偿方法研究

本文研究功率放大器非线性失真对Chirp信号幅频和相频特性的影响及预补偿方法.在雷达系统中,为了获得足够的作用距离,需要增加发射机的发射功率.对输出功率的要求越高,功率放大器(HPA)的工作点就越接近饱和区.这就使得功率放大器的输出信号产生了非线性失真.功率放大器的非线性失真直接影响了发射线性调频(Chirp)信号的质量,对后续的信号处理带来一定程度的影响.以脉冲压缩为例,分析了非线性失真对主瓣宽度和第一旁瓣抑制的恶化.提出了两种建立在直接数字合成(DDS)技术基础上的预补偿方法.通过理论分析和计算机仿真,证明了两种预补偿方法都可以有效地减小非线性失真.最后对影响两种预补偿方法性能的因素和收敛性进行了分析,对两种预补偿方法的结果进行了比较.

Research on Nonlinear Effects of Power Amplifier on Chirp and Methods for Precompensation

This paper focuses on nonlinear effects on both amplitude and phase of a Chirp signal,and also on pre-compensation method for removing these effects.In a radar system,working distance is mainly decided by transmitted power,the more the power,the longer distance the radar can detect.High power amplifier(HPA) often works at saturation point in order to get high output power,but brings on nonlinear effect on output radar signal.The nonlinear effect degrades the performance of Chirp signal greatly.We analyze the main lobe width and first side lobe due to these effects.We propose two methods for pre-compensation based on DDS,i.e.tablechecking method and iterative method.Theory and simulation results show thatthese two methods reduce these effects efficiently.Finally,we analyze the factors that influence the performance of these two pre-compensation methods,as well as the convergence issue for the iterative method,and compare their results.