基于多速率滤波器组的UWB脉冲波束形成方法

在UWB脉冲信号的角度分集接收中,通常的空时处理中通道时延不易精确地控制。该文提出一种适合UWB脉冲信号的基于多速率滤波器组的波束形成方法,避开了时域处理中延迟控制的问题,同时实现了大带宽范围内的均匀一致的频率不变阵列响应。本文具体分析了进行多速率滤波的方式,其优点是滤波器设计简单,运算量与子带数目无关,同时UWB脉冲信号处理的不连续性使得其可以采用比较简单的时域插值算法。仿真实验结果证明了该文方法的可行性和有效性。     

一种时域波束形成系统的工程实现方法

相对于频域波束形成造成的帧间相位不连续,时域波束形成可对阵列输入信号进行精确时延从而得到相位连续的波束。设计了一种时域波束形成系统的工程实现方法。该方法将通道校正和波束形成分开,采用可变分数真延迟滤波器设计方法在线生成通道校正系数和波束权值;采用基于多项滤波和分布式算法实现的FIR滤波器结构,解决了高采样率信号对实时滤波器的要求。与基于乘法器实现的时域波束形成系统相比,该系统不使用乘法器,对FPGA逻辑的消耗也有明显降低,系统可根据资源灵活配置波束数目。     

超宽带雷达自组网的数字波束扫描研究与实现

概要介绍超宽带雷达自组网方式特点及布站方式,重点分析了超宽带信号时延控制形成波束扫描的实现方法,从而解决阵列延时带来的旁瓣以及低增益的问题。与传统相控阵雷达不同的是不再利用移相器,而是估计出各个阵列的时延并通过整数延迟线和FIR分数滤波器进行精确时延补偿,仿真结果表明,该方式波束方向指向性能好,没有旁瓣。     

基于传声器阵列超增益波束形成的语音增强--时域方法

给出了传声器阵列宽带超增益波束形成的时域实现方法。在该方法中,传声器阵列各个阵元输出的语音信号先经过数字延迟线,实现整数倍采样间隔的时延补偿,然后由FIR数字滤波器来模拟超增益波束形成所需的不同频率上不同的幅度和相位加权,最后再把FIR数字滤波器的输出相加即得到时域宽带波束输出。仿真了间距为0.05m的5元均匀线性传声器阵列接收到的端射方向带噪线性调频信号和语音信号,并进行时域宽带超增益处理。仿真结果表明,超增益处理比常规处理的阵增益高8.2dB左右,且具有良好的语音增强效果。     

基于分数时延的宽带数字阵列波束形成

对于宽带数字阵列雷达,传统的波束形成方法会导致天线波束扫描不准和主瓣展宽,为此需要使用时延补偿单元取代传统窄带相控阵中的移相单元。为实现宽带数字阵列各阵元传输时延的精确补偿,引入分数时延滤波器。通过对一种分数时延滤波器设计方法及宽带数字阵波束形成原理的分析,提出针对有载波宽带雷达信号的接收波束形成实现结构。仿真结果表明了该方法的有效性,与传统波束形成方法相比,其性能与理想延时更接近。     

基于Farrow滤波器的宽带数字波束形成技术研究及实现

为获得更高的分辨率,以满足目标识别或精确定位的需要,雷达往往采用宽带信号。对于宽带数字阵列雷达,相同的时延不同的频率会带来相移的不同,窄带波束形成通过相位补偿达到补偿时延的方法会导致宽带波束方向图畸变。为实现宽带数字阵列各阵元传输时延的精确补偿,引入分数时延滤波器。并给出了一种基于Farrow滤波器的宽带数字波束形成系统设计方法。     

基于多项式拟合的宽带NLFM数字分数时延波形产生方法

由于孔径渡越问题，宽带信号的波束形成需要进行时延处理，传统的数字分数时延波形产生方法是在时域上使用分数时延滤波器。目前，大多数宽带发射波束产生的研究均针对线性调频信号，而对于信号特性更复杂且脉压性能优秀的非线性调频(NLFM)信号研究甚少。文中提出了一种宽带NLFM数字分数时延波形的产生方法，并对该信号实现了发射数字波束形成。首先，将时延分为整数时延和分数时延，利用指数多项式拟合处理得到宽带NLFM信号的时域表达式；然后，通过提取参数的方法在直接数字合成器中直接产生分数时延波形；最后，经过整数时延形成宽带NLFM发射波束。仿真实验证明：各阵列单元产生了宽带时延NLFM波束，发射波束的合成方向良好，没有明显失真，时延方法导致的时延误差远低于传统的滤波器方法，且功率合成效率损失可忽略不计，该方法计算简便，对硬件要求不高。     

时域宽带恒定束宽波束形成器的优化设计

为了使用较低阶次的FIR滤波器组实现高精度的时域恒定束宽波束形成器,本文提出了一种优化设计方法。此方法使用了数字延迟线和FIR滤波器组相结合的宽带波束形成器结构。在FIR滤波器组的设计中,使用半定规划的优化方法,使设计波束的主瓣逼近期望波束,同时使用矩阵不等式约束旁瓣高度。在建立最优化问题时考虑了设计频段上的所有频率点,因此可以得到全设计频段上束宽恒定的波束形成器。应用本文的方法,针对8元均匀离散圆弧阵设计时域恒定束宽波束形成器,并与已有方法的设计结果进行了比较,验证了此方法的正确性和有效性。     

基于子阵时延的数字阵列宽带波束形成

数字阵列雷迭是雷达发展的重要方向之一。在宽带信号下,由于孔径效应影响,传统的波束形成方法会导致天线波束指向不准和主辩展宽,为此需要使用时延补偿单元取代传统窄带相控阵中的移相单元。文中以均匀线阵为模型,分析了瞬时带宽理论,并引入了分数时延滤波器的时延方法,实现数字阵列收发传输时延的精确补偿。仿真结果表明：在线阵中,对每个子阵采用分数时延滤波器进行数字波束形成,有效地解决了宽带信号波束图指向偏移,主瓣展宽的问题。     

基于Hermite 插值滤波器的直接延时补偿超宽带波束形成技术研究

超宽带(UWB)信号波束形成是UWB 雷达的关键性技术。传统的波束形成方法存在瞬时带宽和扫描角度受限,波束偏移等问题,直接延时补偿法是避免上述问题的有效途径。该文提出了基于Hermite 插值滤波器的直接延时补偿波束形成方法,理论分析和仿真结果均表明Hermite 插值滤波器幅频特性和群时延特性优于目前常用的Lagrange 和径向基插值滤波器。超宽带线性调频信号实例仿真也表明了该方法在超宽带波束形成性能方面的优越性。      

超宽带阵列天线的接收波束形成研究

针对超宽带接收波束形成问题,提出了一种基于延迟线(tapped delay line)网络结构阵列信号处理方法,应用这种方法修正各路信号,最后对齐信号合成输出。详细分析了基于延迟线的数字波束形成原理,研究了该方法对空间信号的接收性能,并通过仿真验证了这种方法的可行性。分析了阵列天线参数的选取及方向图出现栅瓣的情况。这种方法处理阵列信号简单实用,易于工程实现。     

超宽带载波包络调制及其频谱相关解调

针对超宽带载波包络调制的频谱特性,提出新颖的正交梳状频谱相关解调方法,将超宽带脉冲信号的处理从时域扩展到了频域。阐述了该解调方式的基本原理和设计思路,推导了正交梳状频谱的载波选择原则。对系统性能的分析和仿真证明了频域相关解调的方法有着和时域解调相同的误码率性能。该方法接收机结构简单、成本低,可由全数字电路实现,便于采用其它数字信号处理技术进一步提高系统性能。     

Optical techniques for reconfiguring microwave phased arrays

Very large phased array antennas, particularly in radar and adaptive receive applications as opposed to communications usages, require large amounts of digital data processing for beamsteering, null-formation, imaging, and signal correlation computations. Such processing requires a computational capability which is effectively proportional to the square of the antenna size, and can readily become one of the main design drivers. This processing bottleneck problem is addressed for large phased array antennas. An approach in terms of parallel processing in the optical domain is presented as a potential solution. The defining equations for a phased array antenna system are given, along with the transfer functions for an embedded optical spatial filter control element. Such a control element is shown to have the potential of rapidly reconfiguring a large phased array antenna without the speed penalties associated with conventional sequential addressing methods. A hypothetical phased array antenna, with optical spatial filter control elements, is simulated in a computer model and performance results are presented     

针对线性调频信号的宽带宽角相控阵发射波束形成方法

以线性调频信号为例,揭示窄带相控阵在大孔径宽扫描角情况下不能有效发射宽带高分辨信号的实质。针对线性调频信号,提出2种宽带宽角相控阵发射波束形成新方法,给出了实现示意框图。新方法采用时域数字处理,与时域采用抽头延迟线的FIR滤波器波束形成方法和频域DFT波束形成方法相比,文中方法简单、所需设备量少、易于工程实现。     

Digital Receiver for Laser Imaging Radar

Theoretical basis of the transmitter and high sensitivity receiver design and the problem of waveform design for diode laser imaging radar had been discussed in the past[1] . However, with the extension of the application domains, there are some important technical problems, such as, how to increase the active range of the laser imaging radar system in the applied situation of the both limited maximum power of laser and limited maximum size of system. Another important problem of them is the s…     

Digital Receiver for Laser Imaging Rader

With the extension of the application domains for laser imaging radar, it is necessary to find a new technical way to obtain high technical performance and adaptive ability. In this paper, A new concept of digital receiver of laser imaging radar system is presented. This digital receiver is defined as a time varying parameter receiver which possesses large dynamics region and time domain filter. The receiver's mode, component structure as well as every function of its processing are described. The results and laboratorial data show the feasibility of digital reception. Also, it can exploit the inherent nature of laser imaging radar to obtain high probability of detection.     

基于确知波形的宽带宽角相控阵发射波束形成方法

在大孔径宽扫描角情况下,利用窄带相控阵发射不出去宽带高分辨信号,本文经理论分析说明了这一点,并提出两种基于已知波形的宽带宽角相控阵发射波束形成方法,给出了实现示意框图,通过计算机仿真验证了其可行性.新方法采用时域数字处理,在性能上是最优的.与时域采用抽头延迟线的FIR滤波器波束形成方法和频域DFT波束形成方法相比,文中方法简单,所需设备量少,易于工程实现.     

Implementation of a real-time frequency-selective RF channelsimulator using a hybrid DSP-FPGA architecture

A low cost frequency-selective RF channel simulator architecture is explored in this paper. The technique of quadrature amplitude modulation (QAM) by independent low-pass filtered white Gaussian noise sources forms a rational function approximation (RFA) to the desired Doppler spectrum for flat Rayleigh fading. To simulate frequency-selective fading, this QAM/RFA architecture may be extended by combining delayed outputs from multiple flat fading generators. In this paper, the noise shaping filter considered is in the form of an infinite-impulse-response digital filter followed by an interpolator (upsampler) using linear interpolation. The performance requirements are those in the standard channel simulator section of TIA IS-55-A. The system is implemented almost entirely in the digital domain by use of IF sampling, with the signal processing performed in a high-end floating-point digital signal processor and a field-programmable gate array. The theoretical performance of the simulator is studied with respect to the TIA standard, and limitations of the hardware prototype are identified. A system capable of simulating 12 delay taps, with a processing bandwidth of 5 MHz, can be built at about one-tenth the cost of commercially available channel simulators of comparable performance     

Splitting the unit delay [FIR/all pass filters design]

A fractional delay filter is a device for bandlimited interpolation between samples. It finds applications in numerous fields of signal processing, including communications, array processing, speech processing, and music technology. We present a comprehensive review of FIR and allpass filter design techniques for bandlimited approximation of a fractional digital delay. Emphasis is on simple and efficient methods that are well suited for fast coefficient update or continuous control of the delay value. Various new approaches are proposed and several examples are provided to illustrate the performance of the methods. We also discuss the implementation complexity of the algorithms. We focus on four applications where fractional delay filters are needed: synchronization of digital modems, incommensurate sampling rate conversion, high-resolution pitch prediction, and sound synthesis of musical instruments