NLFM-16QAM雷达通信一体化信号设计与处理方法

Design and processiong methods for NLFM-16QAM radar-communication integrated signals

关键词:  雷达通信一体化  信号设计  非线性调频信号  自相关性能  小波包降噪  自然梯度算法

Key words:  integrated radar and communication  signal design  nonlinear frequency modulation (NLFM) signal  autocorrelation performance  wavelet packet noise reduction  natural gradient algorithm

摘要:

在雷达通信一体化领域,设计出既能实现雷达探测功能又能实现通信信息传输功能的同波形信号是至关重要的一个环节。针对在雷达信号脉冲内对通信信息调制后自相关性能低的问题,提出一种高频带利用率以及低自相关旁瓣的基于非线性调频(NLFM)信号的雷达通信一体化信号形式。将NLFM信号作为16阶正交幅度调制(16QAM)信号的载波,建立NLFM-16QAM雷达通信一体化信号模型,分析该信号的模糊函数以及相关的雷达与通信性能。在此基础上,针对所提出的NLFM-16QAM信号因其通信基带信号的随机性使雷达功能受到影响,从而降低了运动目标探测性能这一问题,将一体化系统的接收端作出改进,提出小波包降噪联合自然梯度算法对NLFM-16QAM信号进行接收处理。仿真结果表明,所提信号的频带利用率明显高于低阶调制的雷达通信一体化信号的频带利用率,在自相关性能方面,所提信号比16QAM-LFM信号的积分旁瓣比降低了23.07 dB,峰值旁瓣比降低了26.08 dB,NLFM-16QAM信号在经过改进接收端的联合算法处理后,运动目标的检测结果获得显著改善。

Abstract:

In the field of radar communication integration, it is a crucial link to design a common waveform signal that can simultaneously support radar detection function and communication information transmission function. In response to the problem of low autocorrelation performance after modulating communication information within radar signal pulses, an integrated radar and communication signal format based on nonlinear frequency modulation (NLFM) signal with high frequency band utilization and low autocorrelation sidelobe is proposed. The core of establishing NLFM-16QAM integrated radar and communication signal model is to take NLFM signal as the carrier of 16 order quadrature amplitude modulation (QAM) signal. The ambiguity function of NLFM-16QAM signal and the related radar and communication performance are analyzed. Noting that the randomness of the communication baseband signal in the proposed NLFM-16QAM waveform can degrade radar functionality and thus reduce moving-target detection performance, we introduce improvements at the receiver of the integrated system. Specifically, a wavelet packet noise reduction is proposed to process NLFM-16QAM signal in combination with natural gradient separation algorithm. Simulation results show that the proposed signal has larger frequency band utilization in comparison with the integrated radar and communication signals of low-order modulation. Compared with the autocorrelation performance of 16QAM-LFM signal, integral sidelobe ratio and peak sidelobe ratio of proposed signal are reduced by 23.07 dB and 26.08 dB respectively. After NLFM-16QAM signal is processed by the joint algorithm of the receiving end, the detection results of the moving target are significantly improved.