【作者】 赵洪立；

【导师】 保铮；

【作者基本信息】 西安电子科技大学 ， 信号与信息处理， 2006， 博士

【摘要】 基于民用机会照射源的无源雷达系统,因为其抗隐身、反侦察和生存能力强等特点,备受各国重视。这种雷达系统利用广播、电视、卫星等外部辐射源,对空中目标,包括隐身飞机或巡航导弹等目标的微弱反射信号进行相干检测,估计目标反射信号的到达方向、到达时间和多普勒频移等参数,并以此来跟踪、识别目标。由于这种系统本身并不像常规雷达探测系统那样需要发射电磁波,且商用无线电台或电视台均工作在VHF频段,因此,它兼顾了常规低频雷达的优点而又具有较强的生存能力和抗隐身特性。实际实验表明该类型雷达将成为现有探测技术的一种有效补充,具有广阔的发展前景和重要的实用(军用及民用)价值。选择什么样的机会照射源是个关键。美国John等人研究表明,FM广播信号具有较短的自相关时间,FM信号当大于1ms的相关时间时近似于理想的白噪声源。因此,调频广播信号作为一种类随机发射信号,具较好脉冲压缩性能、接收机系统误差小而且容易获得的优点。美国人Chadwick研究指出利用双基地探测飞机的关键问题是从强直射信号中分离目标回波,这类似于从强干扰白噪声信号中检测微弱信号。本论文围绕上述热点,以基于商业立体声调频广播信号的被动雷达系统为实验平台,对存在强直达波及其多径干扰下的微弱雷达目标检测技术进行研究。本文的主要工作现归纳如下:1、深入系统地研究了外辐射源雷达系统的信号处理方案,指出高的杂波抑制性能是获得好的检测性能的关键,分析了相关系数和相消比的关系,讨论了采样速率对相消比的影响。提出了基于分数时延估计的地杂波抑制和信号检测地方法。该方法用高分辨率的时间迟延估计技术,把对系统采样率和杂波抑制器滤长度的要求转化到对直达波及多径迟延到达时间的内插估计精度上。该方法不受系统采样速率的限制,当中频采样速率较低、相消器长度较短时,仍然能够由精确的信号内插时延估计求出对应于若干倍中频采样速率的信号时延,提高了杂波抑制性能。对实测数据的处理表明该方法有效地提高了杂波抑制性能。论文还讨论了影响杂波抑制性能的两个因素:双通道不一致特性和系统非线性,提出了通道均衡、直接采样和接收端附加简单模拟相消器的改善方法。2、Griffiths和Long在研究电视波形时,指出机会照射波形的模糊函数是个关键,因为模糊函数的特性将决定距离分辨率、距离模糊间隔、距离旁瓣水平以及多普勒分辨率。商业调频立体声广播信号为在接收端易于解调通常利用副载波,更多还原

【Abstract】 Many countries show considerable interest in the passive radar systems based on the transmitter of opportunity, because of its particularities, such as anti-stealth ability, anti-reconnaissance ability and subsistent ability. Such systems utilize the signals emitted by broadcast station, TV station and secondary planet. The targets such as stealth aircrafts and cruise missiles can be detected by correlation detection. The DOA (Direction Of Arrival), TOA (Time Of Arrival)and Doppler shift can be estimated, and then the targets can be tracked and identified. Such systems don’t emit electromagnetic waves as conventional radar systems do and the frequency of the commercial broadcast lies in VHF band. So that systems have the advantages of good subsistent ability and good anti-stealth ability, besides the advantages of the conventional radar systems. Recent experiments on the passive radars have proved that the passive radar systems are promising as a supplement to the conventional detection techniques. Such systems keep themselves in the foreground and can be utilized in many civil and military fields. As to the important problem that how to choose opportunity transmitter, John (America)’s study indicates that FM broadcast signal’s correlation time is shorter than that of other opportunity signals and that signals are approximately white noise, when the time lag is longer than 1ms. So the FM signals as an opportunity signals have the advantages of good performance of impulse compress, low system error of receiver and easy access. Chadwick’s study indicates that in such system the key technique is to detect weak radar targets with strong direct path signal. The primary contributions and original ideas included in this dissertation are summarized as blow:1. The applicable signal-processing scheme is systemically developed. That the precondition of good detection ability is good performance of clutter suppressor is also pointed. The relation between correlation coefficient and the clutter suppression ratio is presented. The influence of the sampling frequency on the suppression ratio is also studied. The algorithms of clutter suppression and weak signal detection are presented, based on the estimation of the time delay of fractionally spaced clutters. Such algorithms make use of the high resolution of the time delay estimation. The algorithms transform the demand on sampling frequency and length of clutter suppression filter to the demand on TOA estimation precision of the direct path signals and multi-path更多还原