摘要
采用混沌波形设计的统计MIMO雷达可以通过波形分集和空间分集改善检测性能、提高雷达探测性能,以及改善分辨率的同时,还有低截获概率优势。MIMO雷达研究主要存在的问题包括MIMO雷达发射波形的设计、目标特性与杂波特性,目标回波以及自适应滤波几个方面的问题。因此本文主要研究内容如下:
1.本文根据MIMO雷达正交性要求,采用多个混沌信号作为雷达发射波形,通过对混沌信号的模糊函数和它的自相关互相关特性来的计算和仿真,验证了混沌波形作为MIMO雷达发射信号的可行性。
2.针对在常规雷达角闪烁引起目标回波起伏,使雷达检测性能下降的问题,通过MIMO雷达的空间分布设计,研究了有效抑制RCS起伏的天线分布设计方法。根据MIMO雷达系统存在杂波干扰问题,讨论了目标特性与杂波传播特性的问题,并对典型物体的RCS以及多径信道进行了仿真。
3.由于MIMO雷达的回波信号除目标回波外,还存在杂波和接收机的加性噪声等干扰,本文对MIMO雷达回波信号进行了分析与仿真,通过仿真验证了MIMO雷达可以较好解决目标角闪烁问题。
4.为解决MIMO雷达中杂波功率回大于目标回波功率,从而引起虚警的问题,引入自适应滤波器进行杂波对消,通过仿真结果可以看出,接收信号通过LMS滤波器之后,杂波可以有效滤除,从而提高了检测概率。
Statistical MIMO radar which use chaotic signal waveform can improve the detection performance by waveform and space of diversity. Statistical MIMO radar also can improve the resolution ,and have the advantages of low probability of intercept. This paper mainly discusses the problems of MIMO radar waveform design, target characteristics and clutter characteristics, echo signal simulation and adaptive filter .The main contents of study are summarized as follows.
1. According to the requirement of orthogonality ,chaotic signal is selected as the MIMO radar waveform in this paper. The results of calculations and simulations on the ambiguity function, autocorrelation and cross-correlation of the chaotic signals can prove that chaotic signal is appropriate to the MIMO radar waveform;
2.Since target scintillation can deteriorate the detection performance in traditional radar, MIMO radar can effectively suppress this phenomenon by the design of spatial distribution of the antennas. MIMO radar system has clutter interference which reduces the detection performance. So the problem of the target characteristics and clutter characteristics are discussed, and the RCS of several typical objects and multi-path channel are simulated.
3. Echo signal of MIMO radar is composed of the target signal, clutter and the additive noise. By the analysis of echo signals, it is found that MIMO radar can reduce the effect of target scintillation.
4. If the clutter power is too large , false alarm will occur. So an adaptive filter is introduced to slove this problem .The result of simulation can prove that the clutter can be filtered by the LMS filter, and the detection performance of radar targets can be enhanced.
引文
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