基于多相码的MIMO雷达模糊函数

从MIMO雷达的特点出发,在双基地雷达模糊函数基础上,提出了MIMO雷达的模糊函数.MIMO雷达的模糊函数是各双基地雷达模糊函数的线性组合,并且双基地雷达的模糊函数是直角坐标系中目标速度和位置的函数.数值计算表明,MIMO雷达的模糊函数具有直接确定目标位置和速度的能力,并且模糊函数与参考点的选取无关,通过增加发射站和接收站的数目能够提高模糊函数的位置分辨率.     

雷达信号模糊函数仿真分析研究

模糊函数是雷达信号理论中极为重要的一个概念,本文对雷达信号中常用的脉冲调幅信号、线性调频信号和巴克码信号的模糊函数进行了计算仿真,并对其进行了分析研究。     

Radiometric slope correction of synthetic-aperture radar images

The brightness in a SAR image is affected by topographic height variations due to (1) the projection between ground and image coordinates, and (2) variations in backscattering coefficient with the local scattering geometry. This paper derives a new equation for (1), i.e. the radiometric slope correction, based on a calibration equation which is invariant under a coordinate transformation. An algorithm is described to obtain the slope correction from a SAR interferogram, which also enables retrieval of the full scattering geometry. Since the SAR image and interferogram are derived from the same data set, there is no need to match the image with the calibration data. There is also no need for phase unwrapping since the algorithm only uses the fringe frequencies. A maximum-likelihood estimator for the fringe frequency is analyzed and the algorithm is illustrated by processing ERS-1 SAR data. The example demonstrates that the spatial resolution and calibration error are adequate for most applications     

MIMO雷达系统中的Cyclic-Esprit算法

一些人工信号通常具有特殊的时间特性——循环平稳特性,此时,在MIMO雷达中运用传统的DOA估计算法得到的估计结果精度很差,甚至失效。针对这一情况,文中提出了一种适用于在MIMO雷达中运用的Cyclic-Esprit算法,从理论方面推导证明了算法在MIMO雷达中运用的合理性和有效性。仿真实验表明对于具有循环平稳特性的人工信号的DOA估计,算法取得了非常好的效果。     

Acceleration ambiguity function of radar signals and its application

High acceleration of radar targets is analyzed using Acceleration Ambiguity Function(AAF). The acceleration resolution based on AAF is defined. The AAF and acceleration resolution of rectangle pulse signal are derivated and the conclusion that its acceleration resolution is in inverse proportion with the square of its duration is drawn. In the end, these conclusions are applied to the parameter designing and performance evaluation for a certain type of pulse Doppler radar.     

MIMO系统的约束广义预测控制

讨论了输出终端带不等式约束情形的多输入多输出系统，说明了这些约束可以通过修改输入柔化系数而使其得以满足，在柔化系数的选择范围确定过程中，为了避免矩阵求逆，采用利用已知数据辨识参数的方法来确定柔化系数，从而使得问题简化。降低了计算量且加快了收敛速度。     

On the application of coherent optical processing techniques to synthetic-aperture radar

Coherent optical systems are useful for the processing of data collected by sidelooking synthetic-aperture radars. This type of radar, which is useful for generating fine-resolution terrain imagery, has the capability of providing along-track, or azimuth, resolution which is much finer than the azimuth dimension of the radiated beam itself; however, the attainment of this finer resolution requires extensive processing of the received radar signal. In this paper the form of the returning radar signals is discussed, as are the general reasons why optical processing of these signals might be attractive. The required processing can be viewed as a multichannel weighted vector summation, matched filtering operation, or cross-correlation operation; the cross-correlation viewpoint is developed, as is a corresponding optical processor implementation. The role of a conical lens in simplifying reference-function realization is discussed. Finally, a Fresnel-lens interpretation of the recorded radar signal leads to a discussion of the strong physical analogy between a coherent radar system and a coherent optical system.     

EBPSK调制脉冲数据帧串信号的平均模糊函数

基于EBPSK(Extended binary phase shift keying)调制雷达通信机可输出高精度大量程的雷达测距值.同时利用EBPSK调制脉冲数据帧串信号和冲击滤波辅助解调的特殊优势进行高频谱利用率的数字通信.研究针对EBPSK调制脉冲数据帧串信号的特点,根据cooper给出的随机信号平均模糊函数的基本定义,详细推导了该信号的平均模糊函数,并通过实验仿真了平均模糊函数图.结论表明,随机EBPSK调制脉冲数据帧串雷达信号与随机二相码脉冲雷达信号的距离模糊函数类似,即在距离轴上无模糊,而其速度模糊函数则由随机EBPSK调制数据和周期的相参脉冲串共同决定,即在速度轴上呈“梳状”模糊图,其模糊瓣取决于周期脉冲串.     

On the approximation of MIMO capacity

Information theoretical optimization problems related to the resource allocation of wireless cellular and ad hoc networks are not solvable in closed form due to the nonlinear logarithmic representation of the Shannon capacity. This paper introduces functional approximations to the MIMO capacity over flat Rayleigh fading channels, which allow for analytical solutions to network resource optimization problems. The precision of the suggested approximations is assessed and is shown to provide a very close match to the exact capacity expression.     

Timing synchronization using cross ambiguity function for MIMO OFDM systems with distributed antennas

In this letter, we propose a novel timing offset estimation method for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems with distributed antennas using cross ambiguity function (CAF). The proposed algorithm has an impulse-shaped timing metric which allowed it to reduce the uncertainty due to the timing metric plateau. Simulation results show that the mean square error (MSE) performance of the proposed method is significantly improved.     

MIMO体制雷达原理及关键技术分析

在对MIMO雷达的基本原理进行概述的基础上,重点分析了MIMO雷达设计时所涉及的主要关键技术,对关键技术实现的途径及常用方法进行了讨论和分析,最后提出了还需进一步研究的方向和主要内容。     

Principles of high-resolution radar based on nonsinusoidal waves.II. Generalized ambiguity function

For pt.I see ibid., vol.31, no.4, p.359-68 (1989). A generalized ambiguity function for nonsinusoidal coded waveforms that are represented as a train of properly weighted Gaussian pulses is derived and analyzed to study its properties. Computer plots of generalized ambiguity functions of different binary codes, e.g. Barker, complementary, and pseudorandom codes, are presented. The various computer plots show that the desired thumbtack ambiguity function is achievable by nonsinusoidal coded waveforms     

MIMO雷达多目标DOA估计

DOA估计是雷达参数估计方面理论研究的一个重要内容,其主要目的是确定各个信号到达阵列参考阵元的方向角。MIMO雷达可以有效提高DOA估计分辨力和精度得到了广泛的关注,但是MIMO雷达DOA估计算法却比较复杂。因此对MIMO雷达DOA估计的几种主要算法进行了深入系统的研究,通过计算机仿真分析比较了各种不同算法的特点,得到了各种算法的优缺点和局限性,从而为正确分析和处理MIMO雷达回波信号提供依据。     

Target position estimation in radar and sonar, and generalized ambiguity analysis for maximum likelihood parameter estimation

Target position estimation in radar and sonar means joint estimation of range and angle in the presence of noise and clutter. The global behavior of a maximum likelihood (ML) position estimator, and the clutter suppression capability of the system, can be written in terms of a range-angle ambiguity function. This function depends upon signal waveform and array configuration, i.e., upon both temporal and spatial characteristics of the system. Ambiguity and variance bound analysis indicates that system bandwidth can often be traded for array size, and direction-dependent signals can be used to obtain better angle resolution without increasing the size of the array. Wide-band direction-dependent signals (temporal diversity) can be traded for large real or synthetic arrays (spatial diversity). This tradeoff is apparently exploited by some animal echolocation systems. The above insights are obtained mostly from the properties of the range-angle ambiguity function. In general, an appropriate ambiguity function should be very useful for the design and evaluation of any ML parameter estimator. System identification methods and radio navigation systems, for example, can be optimized by minimizing the volume of a multiparameter ambiguity function.     

基于双混沌系统的非线性调频雷达信号及其特性分析

提出了两种双混沌系统的构成方案,通过双混沌系统生成了双混沌信号序列,在此基础之上,利用双混沌信号对正弦波进行调频。双混沌调频(FM)信号具有良好的自相关特性,同时使雷达波形难以辨识。用宽带模糊度函数统计平均方法研究了信号的模糊特性,并对信号的抗干扰性能进行了分析。仿真结果表明,双混沌调频信号具有极佳的距离和速度分辨率,抗干扰能力较强,是一种理想的信号形式。