【作者】 刘勇；

【导师】 王雪松；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2011， 博士

【摘要】 极化信息可以显著提高雷达的目标检测、目标识别与抗干扰性能,在现代防空、反导雷达中具有广阔的应用前景。随着新型高速机动目标的出现,以及战场电磁环境的日趋复杂,雷达极化信息的有效应用面临诸多挑战:一方面,新型导弹、飞机等目标的高速机动会使极化特性起伏更加剧烈,传统分时极化测量体制的固有不足已成为制约该类目标极化特性获取的主要瓶颈;另一方面,随着各种先进的相参、宽带电子干扰技术不断涌现,现有极化抗干扰方法由于受到应用条件限制,难以应对复杂多变的干扰样式。本论文以防空、反导为应用背景,以瞬态极化理论为基础,深入研究了动态目标极化特性测量和极化抗干扰方法,主要内容包括:在动态目标的极化特性测量方面,以导弹、飞机等高速运动目标的极化特性获取为需求,深入研究了动态目标的同时极化测量方法,显著提高了测量性能。(1).以导弹目标为对象,通过分析其在运动状态下的窄带、宽带极化特性,揭示了目标高速运动对极化特性的调制机理,并针对分时、同时两种极化测量体制,定量分析了目标极化特性起伏对测量性能的影响。理论分析和仿真实验结果均表明,对于极化特性快起伏目标,同时极化测量体制具有突出优势,这为极化雷达体制的选择提供了重要参考。(2).针对动态目标的窄带极化特性测量问题,对比分析了频移脉冲和正负斜率线性调频(LFM)两种典型同时极化测量波形的隔离度性能,结果表明,当多普勒频移补偿误差较小时,选择频移脉冲波形会得到更好的测量性能。利用瞬态极化雷达(KD-IPR)开展的外场测量实验,验证了相关结论。(3).针对动态目标的宽带极化特性测量问题,基于正交频分复用(OFDM)原理设计了全极化OFDM波形,并提出了宽带极化散射矩阵测量、一维/二维全极化散射中心特征提取等处理方法。分析结果表明,与传统的宽带正负斜率LFM波形相比,在速度补偿后,该波形具有更好的隔离度性能,能够更加准确的提取目标全极化高分辨信息,且有效消除了“多普勒–时延”耦合误差。在极化雷达抗干扰方面,面向对空监视、跟踪制导及宽带成像的应用背景,针对转发式多假目标干扰、自卫式有源干扰及宽带干扰,提出了几种实用的极化雷达抗干扰新方法。(1).针对转发式多假目标干扰,利用目标回波和干扰信号的瞬态极化特性差异,提出了相应的假目标抑制方法。与现有方法相比,该方法无需估计干扰极化状态,具有更好的实用性。基于实测目标回波数据的实验结果表明,该方法在较低信噪比/干噪比情况下仍能取得有效的抗干扰效果。(2).针对自卫式有源干扰,建立了正交极化二元阵雷达天线的空域极化特性理论模型,提出了两种空域极化抗干扰新方法:一是提出了空域虚拟极化滤波方法,该方法仅利用接收信号幅值来实现干扰极化状态估计,可有效抑制自卫式压制干扰;二是提出了假目标空域极化鉴别方法,该方法利用目标回波和干扰信号的空域极化特性差异来设计处理算法,可有效对抗自卫式欺骗干扰。仿真实验结果验证了这两种方法的有效性。(3).针对逆合成孔径雷达(ISAR)面临的宽带有源干扰,提出了两种宽带极化抗干扰方法:一是以径向距离维输出干扰平均功率最小为准则,提出了宽带极化对消方法,可有效抑制宽带压制干扰;二是利用真实目标和假目标的一维距离像(HRRP)极化相关特性差异,提出了相应的极化鉴别方法,可有效对抗宽带HRRP欺骗干扰。这两种方法能够显著提高ISAR系统在干扰背景下的成像能力。本文研究成果有助于推动瞬态极化信息处理技术从理论走向实用,对于提高防空、反导雷达的目标特性获取和抗干扰能力具有重要参考价值。更多还原

【Abstract】 Polarization information can remarkably improve radar performances of target detection, target recognition and anti-jamming, and has wide application perspectives in modern surveillance and missile defence radars. However, with the appearance of novel maneuvering targets and the more and more complicated electromagnetic (EM) environment, the effective applications of radar polarization information face many challenges. On the one hand, the fast movement of such targets as missiles and airplanes make their polarization characteristics fluctuate more acutely, so the inherent drawback of tradiational alternative polarization measurement scheme has become the main obstacle for acquiring their polarization information. On the other hand, with the appearance of various advanced coherent and wideband electronic counter measures (ECM), available polarization anti-jamming methods are unable to counter sophisticated jamming types due to their limited application conditions. Under the background of air surveillance and missile defence, the polarization characteristic measurement methods of moving targets as well as the polarization radar anti-jamming methods are deeply studied based on the instantaneous polarization theory. The main contents of this dissertation include:In the aspect of target polarization characteristic measurement: To acquire the polarization characteritics of fast moving targets such as missiles and airplanes, the simultaneous polarization measurement method is deeply studied, which can remarkably improve measurement performance.(1). Taking missile targets as an example, their narrowband and wideband polarization characteristics under movement condition are analyzed, and then the modulation mechanism of fast movement on target polarization characteristics is revealed. For alternative polarization measurement shcheme and simultaneous polarization measurement scheme, the effect of target polarization characteristic fluctuation on their measurement performance is quantively analyzed. The results of theorectical analysis and simulations show that simultaneous polarization measurement scheme have prominent advantage for targets with fast fluctuating polarization characteristics. This conclusion provides valuable reference for the choice of polarization radar schemes.(2). To measure the narrowband polarization characteristics of moving targets, the isolation performances of frequency shifted pulse waveform and up-down slope LFM waveform are comparatively analyzed. The results show that better measurement performance can be achieved for frequency shifted pulse waveform when the doppler shift compensation error is small. Field measurement experiments using instantaneous polarization radar (KD-IPR) are performed to prove corresponding conclutions.(3). To measure the wideband polarization characteristics of moving targets, fully polarimetric OFDM waveform is designed based on the principle of orthogonal frequency diversity multiplex (OFDM), and its processing methods are given, including wideband polarization scattering matrix (PSM) measurement and one dimensional/two dimensional full polarization characteristic extraction. The analytical results show that this waveform has better isolation performance compared with traditional wideband up-down slope LFM waveform after velocity compensation, so it can extract target full polarization information more accurately, and can eliminate the“doppler-delay”coupling error as well.In the aspect of polarization radar anti-jamming: For the applications of surveillance, guidance and imaging, several practical polarization radar anti-jamming methods are studied for typical jamming types such as active decoy, self-defence active jamming and wideband jamming.(1). To counter active decoy jamming, the suppression algorithm is put forward based on the instantaneous polarization characteristic differences between target echoes and jamming signals. Compared with available methods, the new method doesn’t need to estimate jamming polarization state, so it is more practical. The results of experiments based on the measured target echoes show that this method can also obtain effective anti-jamming performance under relatively low signal to noise ratios (SNR)/jamming to noise ratios (JNR).(2). To counter self-defence active jamming, the spatial polarization theoretical model of orthogonal polarized dual array radar antenna is established, and then two novel spatial polarization anti-jamming methods are put forward. Firstly, the spatial virtual polarization filtering process is given, which can estimate jamming polarization state by only using the received signal amplitude and counter self-defence suppressive jamming effectively. Secondly, the spatial polarization discrimination method for active decoy is studied. Based on the spatial polarization characteristic differences between target echoes and jamming signals, the processing algorithm is designed to counter self-defence deceptive jamming. The simulation results prove the effectiveness of above two anti-jamming methods.(3). To counter the wideband active jamming of inverse synthesis aperture radar (ISAR), two wideband polarization anti-jamming methods are put forward. Firstly, according to the criterion of minimizing the average jamming signal power in radial range dimension, wideband adaptive polarization canceling (WAPC) algorithm is given, which can effectively counter wideband suppressive jamming. Secondly, using the high resolution range profile (HRRP) polarization correlation characteristic differences between real targets and false targets, the polarization discrimination algorithm is advanced, which can effectively counter wideband HRRP deceptive jamming. These two methods can improve the imaging ability of ISAR under jamming background.The research results of this dissertation are useful for promoting the instantaneous polarization information applications from theory to practice, and are of important reference value for advancing the performances of defence radars in target characteristic acquisition and anti-jamming.更多还原