MIMO雷达发射方向图匹配和波形优化方法

为了匹配MIMO雷达系统给定的发射方向图,采用半正定规划(SDP)来优化发射信号的协方差矩阵．基于该协方差矩阵,利用循环算法(CA)和极小极大法,通过优化波形相位设计出了具有低空域和时域副瓣的恒模发射信号．此外,又提出了用凸规划设计空域失配滤波器和时域失配滤波器的方法,进一步降低了空域和时域副瓣．     

MIMO radar waveform design method via low sidelobe beampattern modification

In the design of the multiple-input multiple-output(MIMO) radar waveform, decreasing transmit beampattern sidelobes could reduce the energy of clutters and false targets from sidelobes and increase the received signal to noise ratio (SNR) so as to improve the angle estimation property. Motivated by this idea, a transmit waveform design method based on low sidelobe beampattern modification is proposed for MIMO radar. First, the transmit waveform cross-correlation matrix can be obtained by the semidefinite relaxation (SDR) technique. Then the essence of our method is to establish an optimization modification model to reduce the beampattern sidelobe by changing the non-diagonal elements of the waveform cross-correlation matrix. Finally, the corresponding transmit beamforming weight matrix is obtained by this modified matrix, and the ESPRIT algorithm is used for the direction of arrival (DOA) estimation. Meanwhile, the feasibility of our method is demonstrated. Simulation results show the superiorities of our method in sidelobe suppression, DOA estimation accuracy and angle resolution.     

一种空时联合优化的MIMO雷达波形设计方法

针对多输入多输出(MIMO)雷达波形设计中空域合成信号的时域特性较差的情况,提出了一种空时联合优化的MIMO雷达波形设计方法．该方法在波形设计中对波形的空域功率分布以及空域合成信号的自相关特性进行了联合考虑．基于空域信号的自相关旁瓣电平以及各阵元信号间的相关性,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,并采用序列二次规划方法与加权迭代方法求解．仿真结果表明,文中所设计的波形不仅能够很好地逼近期望方向图,而且空域合成信号具有较好的自相关特性．     

稳健的MIMO雷达发射波形和接收滤波器联合优化设计

针对杂波条件下目标反射信号方向不确定的情况,提出一种稳健的MIMO雷达发射波形和接收滤波器联合优化设计方法.在考虑各阵元发射功率相等的约束条件下,利用发射加权矩阵构造不确定集范围内关于输出信干噪比(SINR)的Maxmin优化模型;在此基础上,利用序列优化、半正定松弛和Charnes-Cooper转换,将非凸的联合优化问题转化为关于发射波形和接收滤波器的凸优化问题进行迭代求解;最后通过随机向量合成方法计算最终发射波形和接收滤波器,并对算法计算复杂度和收敛性给出分析和证明.所提方法在满足阵元发射功率一致的约束条件下,提高了算法稳健性并降低了计算复杂度.仿真实验证明了算法的有效性.     

采用OFDM-LFM的MIMO雷达高速目标波形设计

单基地多输入多输出雷达由于其宽发射波束的特性而能有效解决目标高速运动跨越发射波束带来的能量损失问题;但是现有波形对速度容忍性较差,高速目标回波匹配滤波能量损失较大．因此,有必要研究适用于高速目标背景下的多输入多输出雷达波形． 文中提出了一种基于正交频分复用线性调频信号的多输入多输出波形． 该波形不同发射通道分时复用一组不同频段的线性调频信号,从而得到带宽相同的可分离多路多输入多输出雷达波形． 仿真结果表明,文中设计的多输入多输出雷达波形能有效降低高速目标回波匹配滤波的能量损失,适用于高速目标背景．     

Waveform Design for MIMO Radar with One-Bit DACs via Block-Sparse Semidefinite Relaxation

Multiple-input multiple-output (MIMO) systems which deploy one-bit DACs are at-tractive in many fields, such as wireless communications and radar. In this paper, the problem of transmit waveform design in MIMO radar system with one-bit DACs is investigated. By appropri-ately designing the transmitted QPSK signal waveforms, the majority of radiated energy can be fo-cused into the mainlobe region(s) by minimizing the integrated sidelobe to mainlobe ratio (ISMR) of beampattern, such that the intensity of backscattered signals from targets can be enhanced. However, the resulting optimization problem which consists of constrained fractional quadratic problem (CFQP) is noconvex. To tackle this problem, a block-sparse semidefinite relaxation meth-od is first utilized to reformulate the CFQP into a reduced convex semidefinite programming (SDP). Further, a customized interior point algorithm (IPA) is developed to solve the small-scale SDP. Finally, the desirable one-bit transmit waveform sequence can be properly synthesized by us-ing Gaussian randomization method. Numerical simulation results demonstrate that the proposed method offer better performance than the state-of-the-art algorithms.     

Adaptive waveform design for target detection in the wideband radar system

The target detection performance of radar can be improved by transmitting a waveform which matches the high-resolution range profile (HRRP) of the target. However, a serious degradation of the autocorrelation property always occurs in the matched waveform, which has a bad effect on radar parameter estimation. To solve this problem, a generalized model of HRRP which consists of the deterministic term and random term is introduced under the consideration of variations in the target impulse response. Based on the study of the generalized likelihood ratio test (GLRT) detector and the objective functions for waveform design, an iterative algorithm with the criteria of maximizing the signal to noise ratio (SNR) and minimizing the minimum mean square error (MMSE) is proposed. Simulation results indicate that the design method can make a tradeoff between the performances of estimation and detection, and sequentially improve the detection performance based on the on-line estimates of the HRRP.     

Y形阵列宽带信号二维来波方向估计

利用Y形阵列结构的特点,提出一种宽带信号二维来波方向的估计方法.该方法在相干信号子空间法的基础上,通过采用流型矩阵展开的方式获得聚焦矩阵,并针对聚焦后的协方差矩阵,利用基于子阵的ESPRIT算法和二维MUSIC算法进行联合估计,从而提高了测向精度且减小了谱峰搜索的范围.理论分析和计算机仿真实验表明,该方法对于非相干信号源和相干信号源都具有较好的估计效果,并具有较低的计算量.     

阵元利用率最高的MIMO雷达阵列结构优化算法

提出了一种多输入多输出雷达阵列结构优化新算法．首先要求在实际物理阵元数最少的条件下能够在接收端获得尽可能多的有效虚拟阵元数,即系统总的物理阵元利用率最高; 然后约束多输入多输出雷达的虚拟阵列满足最小冗余阵的要求,从而提高系统的分辨率并克服栅瓣和高旁瓣的影响．理论分析和算法求解结果都表明,该算法优化出的多输入多输出雷达阵列是收发为同一阵列的非均匀线阵,在物理阵元总数相同的条件下,较其他阵列结构具有更好的波束性能．     

MIMO 雷达迭代降维稳健波束形成方法

Aiming at the transmitted and received steering vectors mismatch problem, an iterative dimension-reducing robust adaptive beamformer for MIMO radar is presented. The General Linear Combined(GLC) method is applied in MIMO radar to obtain the enhanced covariance matrix estimation, and the transmitted and received steering vectors mismatch model is established. The cost function is established based on the desired signal output power maximum principle to estimate the transmitted and received steering vectors. The bi-iteration method is proposed to solve the cost function and it is merely necessary to find out two low-dimensional convex quadratically constrained quadratic programming(QCQP) problems in per iteration. Simulation results show that the proposed method can obtain the higher output signal-to-noise-plus-interference(SINR) under the condition of severe steering vector mismatch than the conventional robust beamformers, and that the proposed method can converge fast so that it has the lower computational complexity.     

星载多发多收SAR多维编码波形设计与分析

多发多收合成孔径雷达(MIMO SAR)解决了传统SAR存在的高分宽幅矛盾。为提高MIMO SAR对通道之间干扰能量的抑制能力,采用多维波形编码技术进行系统设计,并研究了MIMO SAR的波形设计问题。针对两种新型信号形式：正负线调频信号及正交频分复用调制线调频信号,与短时移正交信号(STSO)进行对比分析及成像实验验证。根据MIMO SAR多个孔径同时发射信号、多个孔径同时接收回波的特点,结合多维波形编码技术进行回波处理。在俯仰维,利用数字波束合成技术进行多个子测绘带的划分,实现大测绘带成像;在方位维,利用多通道重构算法将周期非均匀采样的回波恢复为均匀采样,实现高分辨率成像,在此基础上开展新体制SAR发射信号的设计与成像实验验证。实验结果表明,较之其他两种信号,STSO信号的峰值旁瓣比、积分旁瓣比及分辨率等性能最优,对模糊能量抑制更为彻底,在MIMO SAR中性能良好,与传统SAR的性能近似。STSO在MIMO SAR体制中具有良好聚焦性能,且各项成像指标良好,在一定程度可降低系统设计的复杂度。     

MIMO radar waveform design in the presence of clutter and colored noise

The existing MIMO radar waveform design methods only deal with the optimization of radar waveform with the presence of clutter or colored noise, and unfortunately can not get the optimal waveform with the scenario when the clutter and colored noise coexist, which is more realistic in practical applications. To address this problem, a novel MIMO radar waveform design method based on mutual information in the presence of clutter and colored noise is proposed. The proposed scheme considers the influence of the target's response, clutter and colored noise on the optimization of the radar waveform. The mathematical expression for the transmit waveform matrix is achieved by theoretical derivation. What is more important, an optimal pairing of the eigenvectors of the target, clutter and colored noise is given and the power allocation for each antenna is optimized by the water-filling method. Simulation results show that when the total transmit power is 10dB, the proposed method's MI is 8bit and 4bit more than that of the general water-filling method and the method which only considers the pairing of the target's response and noise, respectively.     

双基地MIMO雷达收发阵列互耦条件下目标定位方法

利用均匀线阵互耦矩阵的带状、对称Toeplitz特性,基于子空间原理,提出了一种双基地MIMO雷达目标定位及互耦自校正方法.将对目标二维方位角估计与互耦参数估计相"去耦",不需要任何互耦矩阵信息,且角度估计性能与互耦已知时二维MUSIC算法相近;同时,基于信源二维方位角的精确估计,算法还可以精确地估计出互耦矩阵,从而实现双基地MIMO雷达的互耦自校正.该方法对目标二维方位角与互耦矩阵的联合估计不涉及高维的非线性优化搜索,只需一维搜索,具有较小的计算量.计算机仿真结果证明了本方法的正确性和可行性.     

双基地MIMO雷达目标定位及互耦自校正算法

利用均匀线阵互耦矩阵的带状和对称Toeplitz特性,提出了一种基于旋转不变技术估计目标参数(ESPRIT)的双基地多输入多输出(MIMO)雷达目标定位及互耦自校正算法.该算法通过ESPRIT算法中子阵的选取,将目标二维方位角估计与互耦参数估计相"去耦",角度估计过程不需任何互耦矩阵信息,且估计精度高、分辨力强;基于对目标二维方位角的估计,算法还可以精确地估计出互耦矩阵,从而实现双基地MIMO雷达的互耦自校正.该算法对目标二维方位角与互耦矩阵的估计不涉及任何角度搜索和迭代过程,具有较小的运算量.计算机仿真结果证明了该算法的正确性和可行性。     

低快拍下MIMO雷达收发角度联合估计方法

在多输入多输出(MIMO)雷达中,基于二阶统计特性的子空间角度算法在低快拍条件下的估计性能急骤下降,甚至在单快拍时失效。针对该问题,提出一种扩展阵列孔径的二维联合空间平滑多目标波离方向(DOD)和波达方向(DOA)估计方法。该算法对MIMO雷达的发射端和接收端进行二维联合空间平滑,并利用MIMO雷达虚拟阵列的旋转不变特性对阵列孔径进行扩展,然后根据ESPRIT算法获得目标的DOD和DOA,且DOD和DOA自动配对。与基于二阶统计特性的子空间算法相比,且所提算法在低快拍条件下具有更加优越的角度估计性能,因所提算法能够适用于单快拍条件。仿真结果表明了所提方法的有效性和优越性。     

基于OFDM共享信号的低截获雷达通信一体化波形设计

为了提高雷达通信一体化系统的射频隐身能力,确保作战平台的安全并提升作战能力,提出一种基于截获概率的正交频分复用(OFDM)雷达通信一体化波形设计方法.该方法将截获概率问题转化为最小化雷达通信一体化发射功率的问题,以检测概率和信道容量为约束条件,通过求解Karush-Kuhn-Tucker条件,得到雷达通信一体化系统发射...     

密集阵MIMO雷达阵列模式及其特性

为了对密集阵MIMO雷达不同阵列模式之间的联系进行研究,建立了密集阵MIMO雷达多次快拍信号模型,导出了接收信号相位历史的解析表达式,并通过相位历史表达式揭示了其蕴含的三种阵列模式以及生成机理;结合各阵列模式形成机理分别讨论了三种不同模式阵列特性.最后通过仿真结果对各阵列模式的特性进行了分析.研究结果表明,密集阵MIMO雷达不同阵列模式可带来不同的得益.     

System Design and Signal Processing for Frequency Diverse Array Radar

Frequency diverse array(FDA) radar has been studied for more than 15 years and has attracted a lot of attention due to its potential advantages over the well-known phased array radar.The representative feature of FDA is range-angle-time-dependent transmit beampattern and its underlying properties are continuously revealed in the research. The formulation and exploitation of the transmit diversity with a frequency increment is the fundamental principle, which brings extra degrees-of-freedom(DOFs) in the transmit dimension. As the FDA radar carries additional information in range, it provides more flexibility in signal processing and also brings in new technical issues. This article overviews the state-of-the-art in FDA radar area and its applications, mainly based on the progress in our group. There are two main catalogs in FDA radar area, namely coherent FDA and FDA-MIMO(multiple-input multiple-output) radars. Potential applications including target parameter estimation, ambiguous clutter suppression, and deceptive jammer suppression are discussed.     

Joint adaptive waveform and baseline range design for bistatic radar

The problems of joint adaptive waveform design and baseline range design for bistatic radar to maximize the practical radar resolution were considered. Distinguishing from the conventional ambiguity function （AF）-based resolution which is only related with the transmitted waveform and bistatic geometry and could be regarded as the potential resolution of a bistatic radar system, the practical resolution involves the effect of waveform, signal-to-noise ratio （SNR） as well as the measurement model. Thus, it is more practical and will have further significant application in target detection and tracking. The constraint optimization procedure of joint adaptive waveform design and baseline range design for maximizing the practical resolution of bistatic radar system under dynamic target scenario was devised. Simulation results show that the range and velocity resolution are enhanced according to the adaptive waveform and bistatic radar configuration.     

Pattern synthesis optimization of 3-D ODAR based on improved GA using LSFE method

Pattern synthesis in 3-D opportunistic digital array radar(ODAR) becomes complex when a multitude of antennas are considered to be randomly distributed in a three dimensional space.In order to obtain an optimal pattern,several freedoms must be constrained.A new pattern synthesis approach based on the improved genetic algorithm(GA) using the least square fitness estimation(LSFE) method is proposed.Parameters optimized by this method include antenna locations,stimulus states and phase weights.The new algorithm demonstrates that the fitness variation tendency of GA can be effectively predicted after several "eras" by the LSFE method.It is shown that by comparing the variation of LSFE curve slope,the GA operator can be adaptively modified to avoid premature convergence of the algorithm.The validity of the algorithm is verified using computer implementation.