MIMO雷达发射方向图与波形设计方法研究

发布时间：2018-01-13 17:30

本文关键词：MIMO雷达发射方向图与波形设计方法研究　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】：多输入多输出(MIMO)雷达具有多个发射和接收天线,各发射天线可以发射不同信号,这使得MIMO雷达具有波形分集的优势。根据天线的间距,通常将MIMO雷达分为分布式MIMO雷达和集中式MIMO雷达。在复杂多变的工作环境下,传统雷达所采用的往复扫描的单个窄波束和相对固定的发射波形,很难取得满意的性能,也无法满足多任务、多功能的需求。而MIMO雷达的波形分集优势,使得雷达系统具有更高的发射自由度,可以针对工作场景和需求,灵活的设计发射方向图;可以根据环境信息及时调整发射波形。因此,MIMO雷达方向图和波形设计成为一个很有意义的研究领域。本文从发射方向图逼近、合成信号距离旁瓣抑制、多功能波形、杂波抑制和抗干扰等方面对MIMO雷达波形设计进行了研究。论文的主要工作概括如下:1.从正交波形和具有特定方向图的波形等两方面对MIMO雷达方向图设计进行研究。首先介绍了一种基于梯度下降的正交波形循环设计方法,该方法基于最小化加权积分旁瓣(Weighted Integrated Sidelobe Level,WISL)准则,根据各波形的梯度信息,依次对每个波形进行优化。仿真实验表明该算法与基于最小化峰值旁瓣准则的序列二次规划法性能相当,且可以应用于大规模阵列。针对多波束的方向图设计,利用基于修正的最小化旁瓣模型,设计具有较低旁瓣的多波束方向图;通过调整发射样本顺序和优化初相,有效地抑制了波束方向信号的自相关旁瓣和互相关。最后提出一种基于空时联合优化的MIMO雷达波形设计方法,对集中式MIMO雷达的正交波形设计与具有特定方向图的波形设计建立了统一的优化模型,该方法在实现方向图逼近的同时,可以对感兴趣方向信号的时域自相关旁瓣进行有效抑制。2.初步研究、分析了通过MIMO雷达波形设计来实现同时多功能。首先提出一种MIMO雷达多模波形设计方法,以方向图逼近、波束方向信号的功率谱逼近及频谱逼近等为准则优化波形,所设计的波形可以在期望方向形成多个波束,各波束方向的信号可以具有不同特性,以同时实现搜索、成像和跟踪等功能。在多目标场景中,传统雷达通过波束切换的方式,依次对各目标成像,可减少对于每个目标的驻留时间,从而导致多普勒分辨力的降低。针对此问题,提出一种宽带MIMO雷达波形设计方法,该方法可以实现期望的多波束方向图,波束方向信号具有期望的功率谱特性。通过利用CZT(Chirp-Z Transform)变换来计算各方向信号的离散频谱,有效地降低了计算量。另外,为了在保证分辨率不损失的情况下降低目标回波间的相互干扰,将各期望功率谱随机分布于多个不重叠的子带区域。基于所设计波形,通过应用稀疏重构方法可以实现多目标成像。3.实际场景中目标信息不断变化,需要对波束指向、各目标分配的功率及时调整。针对此问题,提出了一种基于迭代FFT的MIMO雷达快速波形设计方法。该方法分两个独立的阶段:快速方向图综合和空域合成信号优化。首先利用迭代FFT方式设计波形以逼近期望的方向图;然后通过优化波形的初相序列来提高空域合成信号的自相关特性。在初相优化中,采用了最小化积分旁瓣电平(ISL)和加权积分旁瓣电平(WISL)准则来抑制旁瓣。由于该算法的主要计算可由FFT/IFFT实现,因此可以满足实时性要求。4.针对空域合成信号的距离旁瓣抑制,提出了两种方式:脉冲串编码和失配滤波器设计。对于静止或速度较低的目标,脉冲串编码的方式可以在保证方向图不变的情况下,进一步抑制距离旁瓣。而对于较高速的目标,采用一种基于辅助变量的MIMO雷达失配滤波器,可以在一定的信噪比损失(Signal-to-Noise Ratio Loss,SNRLoss)范围下,最小化零频附近多普勒失配下的距离旁瓣。该方式可以在多普勒维展宽距离旁瓣的抑制范围,对多普勒频移具有一定稳健性。5.针对抗干扰和杂波抑制问题,初步研究了MIMO雷达认知发射。为了降低被干扰源侦察到的可能,提出了一种自适应发射置零方法,利用接收到的干扰数据,构造干扰子空间,通过对波形与干扰子空间的正交化,实现自适应发射置零。另外,针对快速运动干扰,通过添加导数约束或利用锥化矩阵可以实现干扰子空间扩展,从而获得零陷展宽。针对空域非均匀杂波的抑制,提出了一种MIMO雷达发射方向图优化设计方法。首先通过发射正交波形对杂波环境进行感知,以发射波形与正交波形回波间的平均相关性作为接收阵列中杂波功率的近似,再根据最大化信杂噪比模型优化发射波形。仿真结果表明,在空域非均匀强杂波背景下,优化后的波形可以有效地提高回波信杂噪比。
[Abstract]:Multiple input multiple output (MIMO) radar with multiple transmit and receive antennas, the antenna can transmit different signals, which makes the MIMO radar with waveform diversity advantage. According to the antenna spacing, MIMO is usually divided into distributed radar MIMO radar and centralized MIMO radar. In the complex work environment, single sweep the traditional radar waveform and the narrow beam is relatively fixed, it is difficult to obtain satisfactory performance, can not meet the requirements of multi task, multi function demand. MIMO radar waveform diversity advantage, so the radar system has a higher degree of freedom for launch, work scenarios and requirements, the design of transmitting pattern flexible; according to the environmental information in a timely manner to adjust the transmitted waveform. Therefore, MIMO radar waveform design pattern and it has become an interesting research field. This paper from the beampattern approximation, synthesis Signal sidelobe suppression, multi function waveform, clutter suppression and anti-jamming of MIMO radar waveform design. The main work of this thesis is summarized as follows: 1. from two aspects and has a specific pattern of orthogonal waveform waveform of MIMO radar pattern design research. This paper introduces a kind of orthogonal waveform loop design method based on gradient descent, this method is based on minimizing the weighted integral side lobe (Weighted Integrated Sidelobe Level, WISL) criterion, according to the gradient information of each waveform, for each waveform optimization. Simulation results show that the algorithm with minimum peak sidelobe performance of sequential quadratic programming method based on two criteria, and can be applied to large scale array. For the multi beam pattern design, by minimizing the sidelobe model based on the multi beam pattern design with low sidelobe by adjusting; Sample order and optimize the launch phase, effectively suppress the beam direction signal autocorrelation sidelobe and cross correlation. Finally, a combined optimization based on space-time MIMO radar waveform design method, design orthogonal waveform waveform design of centralized MIMO radar and has a specific pattern of the optimization model is established and unified, the method in the approximation of direction map at the same time, can be interested in the direction of the signal time-domain autocorrelation sidelobe suppressed.2. preliminary study, analyzed by MIMO radar waveform design to achieve multi function. We propose a MIMO multimode radar waveform design method, the pattern approximation, the power spectrum of the signal beam direction and spectral approximation for the approximation optimization criteria of waveform design waveform can form multiple beams in the desired direction, the direction of the signal beam can have different characteristics, at the same time The search function, imaging and tracking. In the scene, the traditional radar beam switching mode, in order to various target imaging, can reduce the dwell time for each target, which leads to the Doppler resolution is reduced. In order to solve this problem, proposes a wideband MIMO radar waveform design method, multi beam pattern this method can achieve the desired direction of the beam, with the desired signal power spectral characteristics. By using CZT (Chirp-Z Transform) to calculate the discrete spectrum transform direction signal, effectively reduces the amount of calculation. In addition, in order to reduce mutual interference in the guarantee target echo the loss of resolution of the case, the expected the power spectrum of random distribution in multiple non overlapping sub area. The design of waveform based on sparse reconstruction method can be achieved through the application of target information becomes multi target imaging.3. in the actual scene And the need for beam pointing, timely adjustment of power allocation of each target. To solve this problem, we propose a fast iterative MIMO radar waveform design method based on FFT. The method is divided into two separate stages: fast pattern synthesis and spatial synthetic signal optimization. First using iterative FFT method to approximate the desired waveform design the direction of the map; then by optimizing the waveform phase sequence to improve the spatial autocorrelation characteristics of synthetic signals. In the early phase of optimization, the minimization of integral sidelobe level (ISL) and the weighted integral sidelobe level (WISL) criterion to suppress sidelobe. Because the main calculation of the algorithm can be realized by FFT/IFFT, so you can meet the requirements of real-time.4. for spatial synthetic signal sidelobe suppression, puts forward two kinds of methods: pulse string encoding and mismatched filter design for static or low speed, pulse string encoding To ensure the direction map unchanged, further sidelobe suppression. For the high speed target, using a mismatch filter MIMO radar based on instrumental variable, can be in a certain SNR loss (Signal-to-Noise Ratio Loss, SNRLoss) range, the minimization of near zero frequency Doppler lost sidelobe distribution this approach can be inhibited. In the range of Doppler broadening dimension range sidelobe, has certain robustness against.5. interference and clutter suppression of Doppler frequency shift, preliminary research on MIMO radar. In order to reduce the emission of cognitive interference source is detected, we proposed an adaptive transmit nulling method, using interference data receiving the structure of the interference subspace through orthogonal waveform and interference subspace, to achieve adaptive zero emission. In addition, for the rapid movement of interference, by adding derivative constraints By using the cone or matrix can realize interference subspace expansion, so as to obtain the null broadening. In order to suppress clutter of non uniform airspace, proposes a MIMO radar transmit beampattern optimization design method. Firstly, by transmitting orthogonal waveforms for sensing the clutter environment, to launch an average correlation between echo waveform and orthogonal waveforms as approximate clutter power receiving array, and then according to the optimized waveform maximum SCNR model. The simulation results show that the spatial non-uniform strong background clutter, the optimized waveform can effectively improve the signal clutter noise ratio.

【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

【共引文献】