一种正交数字下变频器的高效改进结构

针对传统正交数字下变频器结构计算效率低,首先介绍一种基于混频器后X的改进方法,该方法只能使得计算效果提高1/2N,接着在此基础上利用多相滤波法对混频器后置法进行进一步改进,从而大大减少了数字下变频器的运算量,使得计算效率提高了K倍.最后对上述各种正交数字下变频方法进行算法仿真和计算效率分析对比,结果表明经过混频器后置法与多相滤波法综合改进后的数字正交下变频算法计算效率高,实现效果良好.     

多相滤波的数字相干检波原理及FPGA实现

多相滤波是实现数字下变频及数字相干检波的关键技术,是雷达、声纳和通信等系统中为数字信号处理提供高质量的正交信号的有效手段。文中讨论了多相滤波的基本原理,给出了采用多相滤波的方法对中频带限信号处理的仿真分析,并结合一款脉冲压缩雷达中频数字化接收机的实现方案进行工程验证,结果表明,在技术指标上可有效克服正交通道不一致问题,具有较高的应用价值。     

线性调频信号数字脉冲压缩技术分析

在线性调频信号脉冲压缩原理的基础上,利用Matlab对数字脉冲压缩算法进行仿真,得到了雷达目标回波信号经过脉冲压缩后的仿真结果。运用数字脉冲压缩处理中的中频采样技术与匹配滤波算法,对中频采样滤波器进行了优化,降低了实现复杂度,减少了运算量与存储量。最后总结了匹配滤波的时域与频域实现方法,得出在频域实现数字脉冲压缩方便,运算量小,更适合线性调频信号。     

基于FPGA的脉冲压缩仿真与实现

为解决雷达探测能力与距离分辨力之间的问题,在线性调频信号脉冲压缩的原理的基础上,利用MATLAB软件对数字脉冲压缩算法进行仿真,给出一种基于FPGA分布式算法的时域脉冲压缩实现结构,利用图形编辑和VHDL硬件描述语言混合编程,完成脉冲压缩处理各模块设计以及波形仿真。利用基于分布式算法大大减少数字脉冲压缩的运算量,提高脉冲压缩的效率。     

基于ADSP-TS101的数字正交采样和脉冲压缩的高效算法实现

针对雷达信号处理中数字正交采样和脉冲压缩的大运算量问题，提出了用频域方法把正交采样和脉冲压缩结合实现的高效算法，大大减少了运算量，提高了雷达信号处理的吞吐率和实时性。在ADSP-TS101上，验证了这个算法实现数字正交采样和脉冲压缩的速度性能和精度。     

基于FPGA的脉冲压缩仿真与实现

为解决雷达探测能力与距离分辨力之问的问题,在线性调频信号脉冲压缩的原理的基础上,利用MATLAB软件对数字脉冲压缩算法进行仿真,给出一种基于FPGA分布式算法的时域脉冲压缩实现结构,利用图形编辑和VHDL硬件描述语言混合编程,完成脉冲压缩处理各模块设计以及波形仿真.利用基于分布式算法大大减少数字脉冲压缩的运算量,提高脉冲压缩的效率.     

基于CS的LFM信号脉冲压缩实现算法研究

针对传统的脉冲压缩方法存在着副瓣降低与主瓣展宽的矛盾问题,基于压缩感知理论提出了一种实现对LFM信号脉冲压缩的CS脉压算法。首先在分析传统脉冲压缩与压缩感知的关系的基础上,构建了适用于复数域重构的稀疏基,然后提出了采用构建的稀疏基结合平滑0-范数算法实现脉冲压缩的算法,最后证明了所提的算法脉压后信号不仅能重构出回波的幅度,且保留了信号的相位信息,最后对研究的算法从幅度、相位的重构精度以及重构误差等方面进行了仿真,仿真结果表明CS脉压算法能够在不降低距离分辨率的同时达到降低副瓣的目的,同时能保留回波信号的相位历程,具有较高的重构精度。     

一种直接在中频信号上实现通道均衡的新方法

通道失配严重制约了多通道雷达的性能,诸如旁瓣对消的对消比、数字波束形成的波束旁瓣和单脉冲测角精度等。传统的通道均衡一般是在数字正交下变频之后的基带复信号上通过复数滤波器实现,分析传统均衡滤波器原理后,提出了一种可直接在中频采样后数字正交下变频之前实现通道均衡的新方法,证明了均衡滤波器可以用实系数FIR滤波器完成,仿真验证了该算法的可行性。与传统方法相比,新方法可以降低工程实现的复杂度和运算量,已成功应用于某跟踪雷达中。     

基于CORDIC算法的数字中频检波技术研究

为了解决模拟包络检波器受温度影响大、测试精度不高且丢失相位信息等问题,提出了一种基于CORDIC算法的数字中频检波方案,完成幅度、相位及频率检测功能.首先讨论了数字检波的工作原理,分析了其数学模型,然后给出了基于CORDIC算法的幅度和相位检测方案,并在数字鉴相基础上,介绍了使用一阶差分结构实现数字鉴频的方法,同时分析了差分鉴频中出现的相位模糊问题,给出了如何提高鉴频精度的方法.最后,使用FPGA实现了基于CORDIC算法的数字检波器.通过计算机仿真和应用实例表明,基于CORDIC算法的数字中频检波方案是可行的,并且可以获得较高的测量精度.     

数字下变频与脉冲压缩系统的设计与实现

数字下变频与脉冲压缩一直是雷达信号处理中的关键技术之一。应用现场可编程门阵列(FPGA)的IP核技术,研究了一种基于FPGA的数字下变频与脉冲压缩系统的实时实现方法。首先提出了系统的整体结构,然后介绍了数字下变频模块、脉冲压缩模块及接口模块的设计方法。在单片FPGA上实现了对实际采集的中频Chirp信号进行8K点或2K点可变点数的数字下变频与脉冲压缩处理,通过与Matlab软件计算结果的对比,验证了FPGA实时计算的正确性。最后分析了系统的可实现性与实时性。     

考虑曲率修正效应时粗糙面电磁散射的微扰法

本文在分析传统粗糙面电磁散射微扰法的基础上,给出了一种新的考虑曲率修正效应的微扰法,解决了传统微扰法计算掠入射散射时的误差问题.文中同时采用传统微扰法和考虑曲率修正效应的微扰法对实际粗糙面的后向散射截面做了计算,并与有关实验测量结果做了比较,结果表明无论是中、小角度入射,还是掠入射,采用考虑曲率修正效应的微扰法的计算是准确的.     

A modal radar cross section of thin-wire targets via thesingularity expansion method

A modal radar cross section (RCS) of arbitrary wire scatterers is constructed in terms of singularity expansion method parameters. Numerical results are presented for both straight and L-shaped wire targets and are compared to computations performed in the frequency domain using the method of moments     

Perfectly matched layer for the FDTD solution of wave-structureinteraction problems

The wave-structure interactions are the most usual applications of the finite-difference method, in electromagnetic compatibility and radar cross-section computations. The aim of this paper is to get a detailed insight into the implementation of the perfectly matched layer (PML) technique when dealing with such important applications. The PML is a new technique developed for the simulation of free space with the finite-difference time-domain (FDTD) method. This paper deals with the application of this technique to the solution of wave-structure interaction problems. It is shown that the absorbing layer can be set very close to the structure, provided some specifications are satisfied, with the consequence that the computational requirements of the PML technique are far shorter than those of the other methods of free space simulation     

Approximations for dielectric or plasma scatterers

Two approximate methods have been developed for calculating the radar cross sections of nonconducting bodies. The superposition approximation used to obtain the radar cross sections of dielectric clad bodies requires that the scattering properties of the component parts be known. The modified geometrical optics method, which yields the radar cross sections of dielectric bodies, requires no such initial information. These methods can be applied to some bodies with shapes that cannot be treated by means of the classical boundary-value solutions. Furthermore, the computations required are usually considerably simpler than for the boundary-value solutions even when the latter are obtainable.     

Integral equation solution and RCS computation of a thin rectangular plate

In this work, a new integral equation is employed to calculate the current distribution on a rectangular plate which is illuminated by a plane wave. Numerical results are also obtained for the radar cross section (RCS) of the plate for different angles of incidence and different dimensions of the plate. These results are compared with other RCS computations using geometrical theory of diffraction, physical optics, and variational methods.     

Gallium arsenide injection laser radar

The range capability of gallium arsenide (GaAs) laser radar against extended targets and corner reflectors under both negligible and high background radiation condition is evaluated. The computations are carried out for a space environment. An experimental GaAs laser radar was constructed. The operational results obtained with this radar in the atmosphere against several diffuse targets and a corner reflector are presented.     

A Numerical Study of the Retrieval of Sea Surface Height Profiles From Low Grazing Angle Radar Data

A numerical study of the retrieval of sea surface height profiles from low grazing angle radar observations is described. The study is based on a numerical method for electromagnetic scattering from 1-D rough sea profiles, combined with the “improved linear representation” of Creamer for simulating weakly nonlinear sea surface hydrodynamics. Numerical computations are performed for frequencies from 2975 to 3025 MHz so that simulated radar pulse returns are achieved. The geometry utilized models a radar with an antenna height of 14 m, observing the sea surface at ranges from 520 to 1720 m. The low grazing angles of this configuration produce significant shadowing of the sea surface, and standard analytical theories of sea scattering are not directly applicable. Three approaches for retrieving sea height profile information are compared. The first method uses a statistical relationship between the surface height and the computed radar cross sections versus range (an incoherent measurement). A second method uses the phase difference between scattering measurements in two vertically separated antennas (“vertical interferometry) in the retrieval. The final technique retrieves height profiles from variations in the apparent Doppler frequency (coherent measurements) versus range and requires that time-stepped simulations be performed. The relative advantages and disadvantages of each of the three approaches are examined and discussed.      

对宽带高分辨成像雷达的转发式干扰方法

针对宽带成像雷达的工作方式和特点，提出了一种采用DRFM对宽带高分辨成像雷达的新干扰方法。首先推导了DRFM转发信号的数学模型，阐述了宽带雷达一维成像的基本原理。在此基础上提出了一种采用移频调制对宽带雷达一维成像进行转发式干扰的方法。该方法不但能有效地破坏雷达对真目标的一维成像，并可形成虚假目标一维像。通过仿真并结合实测数据，对该方法进行了验证，结果表明了这种方法的可行性。该方法可对一维和二维成像雷达进行干扰。     

基于模糊聚类的雷达信号分选方法

随着新体制、新技术雷达的不断出现，雷达侦察接收机接收到的雷达信号更加密集和复杂，传统的分选方法已不能对其进行有效分选，模糊聚类法能够利用雷达信号的特征参数有效地分选出常规和非常规雷达信号。文中采用了一种新的模糊聚类分析算法一跟踪法，该方法易实现编程，适用于处理大量数据，仿真实验证明分选结果较理想。     

基于人工鱼群聚类的雷达信号分选算法

随着科技的不断发展,各种新体制雷达的不断出现,使得电磁环境变得复杂多变,这就对雷达信号的处理提出了新的要求。目前普遍采用的基于直方图统计的信号分选方法已经不能满足当前雷达信号分选的要求。文中将人工鱼群聚类算法引入到雷达信号分选中,并对其进行了改进,对雷达信号分选进行了一种新的探索,该方法不需要雷达信号的先验知识,适用于处理未知雷达信号。通过仿真实验证明该算法分选准确率高,为雷达信号分选提供了新的思路。