基于盲方法的外辐射源雷达目标探测研究

发布时间：2018-03-13 15:02

本文选题：外辐射源雷达　切入点：直达波提纯　出处：《西安电子科技大学》2014年博士论文　论文类型：学位论文

【摘要】：外辐射源雷达又称为被动相干定位(PCL)雷达，属于新体制雷达中的一种。与传统雷达不同，外辐射源雷达自身不主动发射电磁波，而是利用各种通信、广播信号（比如调频广播、电视台、GSM基站和GPS卫星等）作为照射源，被动接收目标的反射回波信号实现目标探测和成像。从结构上来说，外辐射源雷达属于双基地雷达配置，使其不易被敌方发现，具有较好的抗干扰和抗反辐射导弹能力；并且借助于超高频和甚高频的照射源特性，外辐射源雷达具有良好的反隐身和低空探测能力；同时具有便携、低成本、无需频谱分配、无电磁污染、无探测盲区等优点。因此，为了应对复杂战场环境下的目标探测问题，外辐射源雷达目标探测已成为一种有效的解决手段，具有重要的研究价值。本论文主要针对简易配置的外辐射源雷达目标探测系统中的若干具体问题，如直达波提纯、杂波相消、参数估计以及数据融合等问题进行深入研究，，所取得的主要研究成果如下： 1、针对复杂战场环境下，接收机周围可能存在多个照射源，照射源基本信息未知（主要是基站方向和信号波形信息），无法区分感兴趣信号和干扰信号，无法确定目标探测中各照射源和目标参数的配对关系等问题，提出利用信号特性来抑制干扰。考虑到大部分通信信号都满足循环平稳的特性，提出利用信号的循环平稳特性估计直达波的方向信息，并抑制其它基站干扰。在目标探测阶段，推导二阶循环平稳和模糊函数的等价性，提出利用二阶共轭循环平稳代替模糊函数，实现对感兴趣信号和目标参数信息的配对。 2、针对实际工程中参考信号包含多径，常规外辐射源雷达参考通道和预警通道都需要杂波相消的问题，提出在预警通道中利用盲源分离方法直接分离直达波和目标回波信号，达到减少运算量和提高目标回波信号信噪比的目的。针对常规盲源分离不适用于外辐射源雷达中病态矩阵的问题，提出利用循环平稳特性来抑制干扰，达到增强弱目标信号的目的，在天线个数少于信号源个数的欠定情况，本方法同样适用。在信号分离阶段，针对实际混合信号中还混有噪声的问题，提出鲁棒的斜投影方法来抽取目标回波信号。 3、考虑到OFDM信号在同步和抗干扰方面的优点，提出基于OFDM信号特性的外辐射源雷达目标探测。针对外辐射源雷达中参考信号信息可能无法直接获取的问题，提出利用信号特性来估计OFDM信号信息。具体考虑到OFDM模糊函数中的副峰是由导频的周期性造成的，并且模糊函数等价于二阶循环平稳，提出利用二阶循环平稳估计导频的周期性，从而能够确定导频的位置信息，继而实现杂波信道脉冲响应估计和直达波重构。 4、针对目前通信广播系统大都采用OFDM调制信号，并且支持SFN结构的情况，提出基于OFDM-SFN的外辐射源雷达系统提高目标探测的可靠性。但在SFN中，多个信号从不同的方向照射到目标，极有可能造成大时延扩展。并且OFDM发射正交子载波，对载频频偏很敏感。针对这两个问题，在没有参考信号信息的情况下，提出在接收通道中利用阵列天线把大时延转化为小时延，建立新的张量接收模型，并利用联合对角化方法同时估计波束、时延和频偏三个矩阵变量，解决频域盲源分离算法在大时延扩展中估计精度不高的问题。 5、针对OFDM-SFN中存在的大时延，提出另一种基于循环移位和空时编码的收发方式，接收端使用单天线就能对抗大时延，达到简化接收端系统配置的目的。并针对SFN多站定位中，常规定位算法存在两步估计误差的问题，提出基于OFDM信号特性的直接目标定位方法。相比常规的定位方法，本方法能够获得更高的定位精度，尤其是在目标回波信号低信噪比情况下。
[Abstract]:Passive radar is also called passive coherent location (PCL) radar is a new radar. Unlike conventional radar, passive radar does not actively emit electromagnetic waves, but the use of a variety of communication, broadcast signals (such as FM radio, television, GSM base station and GPS satellite) as radiation source, target detection and imaging echo signal receiving passive target realization. Structurally, passive radar belongs to bistatic radar configuration, it is not easy to be found, has a good anti interference and anti radiation missile capability; radiation source characteristics and with the help of UHF and VHF, passive radar has good anti stealth and low detection capability; it is also portable, low cost, no spectrum allocation, no electromagnetic pollution, the advantages of IOBSS. Therefore, in order to deal with the complex battlefield environment for target detection The target detection of the external radiation source radar has become an effective solution and has important research value.
This thesis focuses on the simple configuration of the passive radar target detection system in some specific issues, such as direct wave purification, clutter cancellation, in-depth study on the issue of parameter estimation and data fusion, the main results are as follows:
1, in view of the complex battlefield environment, the receiver around there may be a number of radiation sources, radiation source unknown basic information (mainly the base station and the signal waveform information), interest can not distinguish between signal and interference signal, unable to determine the matching relationship such problems as the irradiation source and target detection parameters, is proposed to suppress interference using the signal characteristics. Considering that most of the communication signal to meet the cyclostationarity, the paper estimates the direct wave direction information based on cyclostationarity of signals, and suppress other base station interference. In the detection phase, the equivalence of two order cyclostationary and fuzzy function, put forward by two order conjugate cyclostationary instead of fuzzy function. The signal of interest and target parameters matching of information.
2, the reference signal contains multipath in actual engineering for the conventional passive radar reference channel and warning channels need to clutter cancellation problem, proposed direct separation of direct wave and target echo signal in the early warning channel using blind source separation method to reduce the computation and improve the echo signal SNR for. The conventional blind source separation does not apply to external radiation source in the problem of ill conditioned matrix radar, is proposed to suppress the interference using cyclostationarity, to enhance the weak target signal to the less number of antennas less than the number of signal sources, this method is also applicable. In signal separation stage, according to the actual signal is mixed the noise problem, to extract the target echo signal is proposed. The oblique projection method
3, considering the advantages of OFDM signal in synchronization and interference, OFDM signal characteristics of external radiation sources based on radar target detection is proposed. The reference signal information may not be directly access problems for foreign radars, it is proposed to estimate the OFDM signal by using signal characteristics. Specific information considering the OFDM fuzzy function in the side peaks is caused by a periodic pilot, and fuzzy function equivalent to two order cyclostationarity, using two order cyclostationary estimation of periodic pilot, which can determine the location of the pilot, and then realize the clutter channel impulse response estimation and direct wave reconstruction.
4, aiming at the communication and broadcasting system mostly adopts OFDM modulation signal, and the structure of the SFN support, OFDM-SFN is proposed based on the passive radar system to improve the reliability of target detection. But in SFN, a plurality of signal from different direction of irradiation to the target, is likely to cause large delay spread and OFDM emission is. Sub carrier, the carrier frequency offset is very sensitive. To solve these two problems, in the absence of reference signal information, proposed in the receiving channel by using antenna array to delay into time delay, a new tensor receiver model, and uses the joint diagonalization method and beamforming, delay and frequency offset three matrix variables, frequency domain blind source separation algorithm to solve the estimation problem of high precision in large delay spread.
5, according to the large delay of OFDM-SFN, puts forward a cyclic shift and space-time encoding transceiver based on single antenna receiver can withstand large delay, to simplify the receiving end system configuration. And based on the SFN multi station positioning, conventional localization algorithm error estimation problem of the two step forward the direct target location method based on OFDM signal characteristics. Compared with conventional positioning method, this method can obtain higher positioning accuracy, especially at low signal target echo signal SNR.

【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN958

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