雷达极化域变焦角反组合体对抗方法:抗质心式干扰

Radar Polarization Modulation Countermeasures for Combined Corner Reflector:Anti Centroid Jamming

弹载雷达是实现精确制导的重要传感器,在末制导阶段通常采用单脉冲模式以实现对目标的精确跟踪.角反射器质心干扰是应对弹载雷达跟踪的一种重要的无源干扰方式.在雷达跟踪阶段,舰船释放的角反射器与舰船位于雷达的同一分辨单元,单脉冲测量角度指向两者质心,由于角反射器的雷达回波一般强于舰船,单脉冲测角被诱偏,末制导雷达的跟踪点往往偏向角反射器.随着舰船的快速机动,二者之间的距离逐渐变大,末制导雷达会出现目标“失跟”,使得舰船得以逃脱.对抗质心式干扰本质上是解决未分辨多目标的估计问题,通常分为两步,一是检测到目标后判断是否为“目标+干扰”的混合体,二是从混叠的回波信号中准确测量目标参数.在质心干扰存在性检测方面,主要有波形类方法和统计类方法.前者通过分析目标回波的特征差异检测干扰,例如信号盒形分析、小波变换等,此类方法存在经验判决实际性能有限;后者将“混合体”视作多目标,建立单脉冲比统计模型,通过似然比检测实现干扰存在性判决,此类方法模型推导复杂,且仅适用于单个干扰情况.在目标参数测量方面,干扰抑制类方法利用目标和干扰的极化散射特性差异,通过极化滤波抑制干扰,提升单脉冲测角精度,然而需要干扰极化特性或干扰与目标幅度比等先验信息;而多目标测量方法以单脉冲统计模型为基础,构造统计量实现多目标的角度估计,例如矩估计、极大似然估计等.此类方法存在仅适用于单个干扰、依赖正确的统计模型等不足,并且需要大量脉冲精确估计统计模型参数,在实际应用中受限.舰船目标包含了丰富的散射机理,而角反组的散射机理相对单一,两者极化信息差异明显,可用于提升角反干扰的检测与抑制.然而,现有极化单脉冲测角方法均采用多通道方法处理极化信息,目标间的散射特性差异利用不够充分,实际应用时效能有限.在研究雷达极化过程中,特定极化下相邻目标的合成回波差异很大.通过极化域变焦处理调控雷达收发极化抑制角反回波,可以实现舰船目标角度的准确测量.本文针对角反组合体质心干扰,立足于极化域变焦超分辨理论,分析了极化阵列雷达的特征波束和单脉冲测角的统计分布,阐述了“舰船+角反”混合体检测以及角反干扰抑制原理;在此基础上,结合角反与舰船的极化散射特性,建立了角反质心干扰信号模型,提出了干扰存在性检测与舰船测角算法,实现了抗角度诱偏.仿真结果表明,本文所提方法测角精度可达0.1倍波束宽度,在-20 dB极化隔离度下仍可有效测量,综合质心干扰对抗成功率可达80%以上.

Missile-borne radar is an important sensor for precise guidance.In the terminal guidance stage,monopulse mode is usually used to track the target accurately.Centroid jamming of corner reflector is an important passive jamming method for ships to counter anti-ship missiles.In the radar tracking stage,the corner reflectors released by the ship are in the same resolution unit with ship,and the mono-pulse measurement angle points to their centroid.Since the radar echo of the corner reflector is usually stronger than that of ship,the mono-pulse measurement angle is decoded,and the tracking point of the terminal guidance radar is biased to the corner reflector.With the rapid maneuvering of the ship,the distance between them gradually becomes larger,which will cause the“loss track”of ship.The anti-centroid jamming is essentially an estimation problem of unresolved multiple targets,which is usually divided into two steps:one is to determine whether the target is a mixture of target and corner reflector after detection;the other is to accurately measure the target parameters from the coupling echo signal.In the aspect of the existence detection of centroid jamming,there are mainly waveform method and statistic method.The former detects jamming by analyzing the characteristic difference of target echo,such as signal box shape analysis,wavelet transform,etc.The empirical judgment of this method is limited in practical performance.The latter regards the mixture as multiple targets,establishes the statistical model of mono-pulse ratio,and realizes the jamming existence judgment through the likelihood ratio detection.However,the models are complicated to deduce,and only apply to the case of single jamming.As for the target parameter measurement,jamming suppression methods which suppress the jamming through polarization filtering improve the mono-pulse measurement accuracy.However,prior information such as the jamming polarization characteristics or the amplitude ratio between the jamming and the target is required.Based on the mono-pulse statistical model,statistics are constructed to achieve multi targets angle estimation,such as moment estimation,maximum likelihood estimation,etc.This method is limited in practical application because it only applies to a single jamming and depends on a correct statistical model,also requires a large number of pulses to accurately estimate the parameters of the statistical model.The ship target contains abundant scattering mechanism,but the scattering mechanism of the corner reflector array is relatively single,and the polarization information of the two groups is different,which can be used to detect and suppress the corner reflector jamming.However,the existing polarization mono-pulse angle measurement methods adopt the multi-channel method to process the polarization information,and the scattering characteristic difference between the targets is not fully utilized,so the efficiency is limited in practical application.In the study of radar polarization,the synthetic echoes of adjacent targets under specific polarization states are very different.The accurate angle measurement of ship target can be achieved by adjusting the polarization states to suppress the corner reflector through the polarization modulation processing.Based on the theory of polarization modulation super-resolution,this paper analyzes the statistical distribution of characteristic beam and mono-pulse angle estimation for polarization array radar under the condition of centroid jamming of corner reflectors.Moreover,the principle of“ship-reflector”mixture detection and centroid jamming suppression is explained.On this basis,combined with the polarization scattering characteristic of corner reflector and ship,the corner reflector centroid jamming signal model is built.Then,the algorithm of jamming presence detection and angle estimation for ships is proposed and anti-angle induced deflection is realized.The simulation results show that the angle estimation accuracy of the proposed angle estimation method can achieve 0.1 times beamwidth,in addition,is valid with-20 dB polarization isolation.The rate of successful anti-centroid jamming is more than 80%.