基于外辐射源信号的无源雷达关键技术研究

发布时间：2018-08-05 16:29

【摘要】：现代战争在时域上表现为实施谋略、策划、博弈和评估等过程，在空域上表现为控制陆、海、空和天等主权的争夺。无论在时域还是在空域，信息的获取、处理与应用尤为重要。随着高新技术武器装备的飞速发展，目标的信息成为敌我双方控制的焦点，从某种意义上讲，现代战争就是信息战。军用雷达是目标信息的传感器，在现代战争中的主要功能为目标探测、定位、跟踪、分类、成像、识别、告警和传送，其重要意义不言而喻。然而随着反雷达技术的迅速发展，任何军用雷达都将面临着隐身、反辐射摧毁、低空突防及综合电子干扰等四大威胁。基于外辐射源信号的无源雷达（Passive Radar），利用多通道在不同区域进行空间分集接收处理隐身目标的非后向散射能量，实现抗隐身；使用外辐射源信号作为发射信号，反辐射导弹无的可寻，天然具有抗反辐射导弹的功能；采用MIMO体制，增加双基角，可有效改善低空探测性能，实现抗低空突防；借用干扰源信号作为发射信号，可通过多站或单站接收对干扰源实施有效定位跟踪，达到抗干扰的目的。因此受到各国雷达研究者的广泛关注。本文针对GSM或DVB-T作为外辐射源，，从系统的可行性、构成以及理论算法等方面，对无源雷达的关键技术开展了深入研究。具体体现在以下几个方面：（1）提出改进的基于阻塞信号的自适应波束形成方法用于提取直达波信号参考信号是外辐射源雷达相干检测的基准信号，直接影响到目标信号的检测性能。仅利用普通波束形成可能导致获得的信号不纯净，而直接利用自适应波束形成也可能无法获得主基站的直达波信号。本文提出一种基于阻塞信号的自适应波束形成方法，在主基站直达波来波方向处形成主瓣，同时在其他比较强的干扰方向上形成零陷。首先将阵列天线接收信号中主基站直达波信号消去，然后利用自适应波束形成算法求得最优波束形成权值因子，再进行波束形成以获得主基站的直达波信号。首先通过仿真数据验证了所提方法的有效性，然后利用实测数据进行对比分析，实验结果表明所提方法相对于传统的LCMV自适应波束形成方法性能更好，更适合于工程实践。（2）先时域相消后波束形成的无源雷达干扰抑制方法由于外辐射源雷达采用第三方非合作信号作为发射源，接收机不仅能够接收到主基站的发射信号，而且能够接收到附近其他基站发射的同频干扰信号和多径干扰，同时受到环境噪声的影响。本文提出首先利用时域干扰相消算法，消除阵列天线各个阵元中接收到的主基站直达波和多径干扰，然后再对天线各个阵元中的剩余信号进行稳健自适应波束形成。在直达波和多径干扰消除的基础上，将天线的全部自由度应用在抑制同频基站的干扰上，从而能够获得更好的在空域上抑制同频干扰的效果。在噪声环境中，本文考虑到可能存在的直达波残留，提出改进的小波重构算法，选择含目标成分较多的低频层进行重构，而非传统方法中的低频层，根据信号与直达波的差别进行选择性重构。仿真结果表明，本文所提出的小波阈值去噪方法，不仅对噪声有良好的抑制效果，而且对残留的直达波干扰也能有效去除。（3）基于OFDM信号的无源雷达杂波信道估计本文针对OFDM(Orthogonal Frequency Division Multiplexing)外辐射源雷达探测存在的问题，提出基于信号特性的处理方法，研究基于OFDM信号调制特性的外辐射源雷达杂波信道状态信息估计方法。针对该体制雷达中纯净的直达波信号获取问题，提出基于模糊函数的方法提取导频的周期信息，从而得到导频的位置信息，然后利用导频信息得到杂波信道脉冲响应信息估计。相比常规的处理方法，本文方法能够在参考信号包含多径时得到正确的杂波信道状态信息。（4）基于马尔可夫链蒙特卡罗（Markov Chain Monte Carlo, MCMC）过程权值优选的改进的粒子滤波跟踪算法在外辐射源雷达定位中，观测量有信号到达角、信号时差、信号的多普勒频率等，对应于已有的定位方法有很多，如测向定位法、时差定位和差分多普勒定位法，以及融合多种参数和方法的联合定位法等等。本文选择TDOA和DOA的联合定位方法，提高定位精度和稳定性。在跟踪方面，针对外辐射源目标跟踪中粒子滤波退化问题，研究权值优选的粒子滤波和基于MCMC过程的粒子滤波算法，并在对两者分别进行优劣分析的基础上提出了基于MCMC过程权值优选的粒子滤波算法，结合了两者的优点。实验结果表明，本文算法能够在一定程度上解决了粒子多样性丧失的问题，提高了跟踪精度。（5）基于多频段DVB-T信号和时频分析法的无源雷达ISAR成像目标的运动会导致ISAR成像模糊，因此，在传统的雷达成像方法中，需要花大力气做回波的距离对准和相位对准的运动补偿。本文选择了多频段的DVB-T信号，通过获取非相邻通道的信号，巧妙的扩展了信号频带，使频带足够宽从而在成像中获得足够高的分辨率。本文提出利用时频分析的方法，避免复杂的运动补偿，只要在距离向上对准，多普勒频率即可认为是非时变的。这在很大程度上减少对运动补偿的依赖，使目标在做较为复杂的运动时也能得到清晰的成像结果。并且，针对噪声较大的情况下的成像，在采用了短时傅立叶变换（STFT）的时频分析方法的基础上，利用CLEAN算法，通过对图像的解卷积滤波，去掉噪声带来的干扰，提取出散射点的位置信息。对比一般的成像算法，仿真实验证明STFT+CLEAN算法的结果更为清晰准确。
[Abstract]:In the time domain, the modern war shows the process of implementing strategy, planning, game and evaluation. In the airspace, it represents the contention of controlling land, sea, air and heaven. It is particularly important to obtain, handle and apply the information, whether in the time domain or in the airspace. With the rapid development of high-tech weaponry, the information of the target is controlled by both the enemy and the enemy. In a sense, in a sense, modern warfare is information warfare. Military radar is the sensor of target information. The main functions of the modern war are target detection, location, tracking, classification, imaging, recognition, alarm and transmission. However, with the rapid development of anti radar technology, any military radar will be used. It faces four threats: stealth, anti radiation destruction, low altitude penetration and integrated electronic jamming.
The passive radar (Passive Radar) based on the external source signal is used to receive the non backscatter energy of the stealth target in different regions, and to achieve the anti stealth. Using the external radiation source signal as the transmitting signal, the anti radiation missile is not available and has the function of anti radiation missile, and the MIMO system is adopted. Adding double base angle can effectively improve low altitude detection performance and achieve low altitude penetration. Using interference source signal as a transmitting signal, effective positioning and tracking for interference sources can be implemented through multiple stations or single stations to achieve the purpose of anti-jamming. So it is widely concerned by radar researchers in various countries. In this paper, GSM or DVB-T is used as an external source of radiation, In this paper, the key technologies of passive radar are studied from the aspects of system feasibility, structure and theoretical algorithm.
(1) an improved adaptive beamforming method based on blocking signal is proposed to extract direct wave signals.
The reference signal is the reference signal of the coherent detection of the external radiation source radar, which directly affects the detection performance of the target signal. Only using the common beam formation may lead to the inaccuracy of the obtained signal, and the direct use of adaptive beamforming can not obtain the direct wave signal of the main base station. The main base station is formed in the direction of the main base station directly reaching the wave direction. At the same time, the zero sink is formed in the other strong interference direction. First, the direct wave signal of the main base station in the array antenna receiving signal is eliminated. Then the adaptive beam formation algorithm is used to obtain the optimal wave beam formation weight factor, then the beamforming is made to obtain the beamforming. The direct wave signal of the main base station. First, the effectiveness of the proposed method is verified by the simulation data. Then the measured data are compared and analyzed. The experimental results show that the proposed method is better than the traditional LCMV adaptive beamforming method and is more suitable for engineering practice.
(2) passive radar jamming suppression method with time domain cancellation and beamforming.
Because the external radiation source radar uses third party non cooperative signals as the emission source, the receiver can not only receive the transmitting signal of the main base station, but also receive the same frequency interference signal and multipath interference emitted by other nearby base stations, and it is affected by the environmental noise. The direct and multipath interference of the main base station received in each antenna element is listed, and then the robust adaptive beamforming is made to the remaining signals in each antenna element. On the basis of the elimination of the direct and multipath interference, all the degrees of freedom of the antenna are applied to the interference of the same frequency base station, and the better in the space can be obtained. In the noise environment, in the noise environment, this paper proposes an improved wavelet reconstruction algorithm to reconstruct the low frequency layer with more target components, instead of the low frequency layer in the traditional method, and the selective reconstruction of the low frequency layer in the traditional method. The proposed wavelet threshold denoising method can not only suppress the noise but also remove the residual direct wave interference effectively.
(3) passive radar clutter channel estimation based on OFDM signal
In this paper, in view of the problems existing in the detection of OFDM (Orthogonal Frequency Division Multiplexing) external radiation source radar, this paper proposes a processing method based on the signal characteristics, and studies the estimation method of the state information of the clutter channel based on the modulation characteristics of OFDM signal. Based on the fuzzy function method, the periodic information of pilot is extracted and the position information of the pilot is obtained. Then the estimation of the impulse response information of the clutter channel is obtained by using the pilot information. Compared with the conventional method, the method can get the correct information of the clutter channel state when the reference signal contains the multipath.
(4) Improved particle filter tracking algorithm based on Markov Chain Monte Carlo (MCMC) process weight optimization
In the location of the external radiation source radar, the observation has the signal arrival angle, the signal time difference, the Doppler frequency of the signal and so on, corresponding to the existing positioning methods, such as the direction finding location method, the time difference positioning and the difference Doppler location method, and the combination of various parameters and methods, etc.. This paper selects the joint location of TDOA and DOA. In the field of tracking, the particle filter and particle filter algorithm based on the MCMC process are studied, and the particle filter algorithm based on the weight optimization of the MCMC process is proposed on the basis of the analysis of the two. The experimental results show that the algorithm can solve the problem of loss of particle diversity to a certain extent and improve the tracking accuracy.
(5) passive radar ISAR imaging based on multi band DVB-T signal and time-frequency analysis method.
The motion of the target will lead to the blurred ISAR imaging. Therefore, in the traditional radar imaging method, it is necessary to take great effort to compensate the distance alignment and phase alignment of the echo. This paper selects the DVB-T signal of the multi frequency band. By obtaining the signals from the non adjacent channels, the signal frequency band is skillfully expanded to make the frequency band wide enough to be in the imaging. The method of time frequency analysis is proposed to avoid complex motion compensation. As long as the distance is aligned, the Doppler frequency can be considered as non time-varying. This reduces the dependence on motion compensation to a large extent, and makes the target clear imaging results in a more complex motion. And, Based on the time-frequency analysis method of short time Fu Liye transform (STFT), based on the time-frequency analysis method of short time Fu Liye transform, the CLEAN algorithm is used to extract the position information of the scattering point by removing the deconvolution filtering of the image and removing the noise caused by the noise. Comparison of the general imaging algorithm and the simulation experiment prove the result of the STFT+CLEAN algorithm. It's more clear and accurate.
【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.51

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