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。     

一种恒定束宽的宽带自适应波束形成算法

宽带波束形成是相控阵雷达数字信号处理的难点。针对目前宽带波束形成只能满足单一恒定束宽或自适应情况,为兼具两种优势使雷达工作状态更佳,文中基于最小二乘算法提出了一种自适应波束形成方法,该方法通过获得自适应参考波束图,确定波束图恒定范围根据最小二乘算法求取其他频点权值,并进行宽带波束形成。该方法不仅能保证恒定柬宽,而且可实现自适应零陷控制。仿真实验证明了算法的有效性。     

二次下变频实现宽带数字波束形成

宽带相控阵宽角扫描波束形成中,常用模拟延时线技术解决复包络偏移问题,但硬件的高代价阻碍其实际应用。本文在基于跟踪状态及发射线性调频信号的假设下,提出一种二次下变频方法实现宽带数字波束形成,本方法首先对阵元级接收数据进行模拟混频实现去斜,数字域再进行二次下变频,相位补偿后实现波束形成,最终通过傅氏变换获得散射点信息。     

基于开窗结构和寄生单元的双陷波超宽带天线

设计了一种具有双陷波特性的平面超宽带天线。超宽带基础天线的馈电采用渐变式阶梯阻抗匹配结构作,使得天线具有了宽阻抗匹配能力。通过在椭形辐射器内进行开窗,以及在地面添加矩形寄生单元,实现了天线的双陷波特性。测试结果表明,该天线的工作带宽(VSWR<2）为3.1~10 GHz,工作在超宽带(UWB)频率范围,两个陷波分别在3.3~4.0 GHz和5.0~5.85 GHz,可以应用于WiMAX和WLAN频段的信号抑制。仿真与实测结果表明,该天线结构简单、实现了良好的陷波功能,能够较好地应用于超宽带通信系统中。     

宽带阵列通道均衡的工程实现方法研究

对于宽带数字阵列雷达而言,通道之间的幅相特性不一致(即通道失配)会影响雷达阵列信号处理的性能,需要对各通道进行通道均衡来补偿通道失配的损失。基本的通道均衡算法分为时域、频域以及自适应均衡算法,文中通过仿真比较了各类型算法的均衡能力,并着重考虑了参考通道的选择对均衡结果的影响,由此得到通道均衡的最优解决方法。最后,通过雷达工程实验测试,验证了文中宽带通道均衡方法的有效性及最优结果,所得结论对于实际工程设计中改善宽带波束性能具有一定借鉴意义。     

基于子阵的宽带数字恒定波束形成技术

主要研究了基于子阵的宽带恒定波束形成方法,探讨了子阵带宽、子阵大小和最大波束偏移角三者之间的约束关系,最后给出了在子阵级实现低副瓣宽带波束形成的条件。     

超宽带通信系统中同步算法研究

超宽带通信技术近年来受到广泛关注,其中同步问题系统性能的关键因素。研究了超宽带通信系统的定时同步问题,提出了一种粗同步与细同步相结合的同步算法,以TH-UWB-PAM信号系统为例,首先利用脏模板理论进行粗捕获,完成帧一级的同步,然后在捕获的基础上利用滑动相关完成细同步,通过对加性高斯白噪声（AWGN）和超宽带（UWB）多径信道进行了同步算法性能仿真,实验结果表明了该同步算法的可行性,能够获得复杂度和同步性能的良好折中,且在一定信噪比条件下能获得良好的同步精度。     

信息管理中UWB系统信道估计与均衡算法及实现

通过介绍UWB技术的发展现状,着重阐述了MB-OFDM UWB通信系统的物理层帧结构和信道模型。在分析最小二乘(LS)信道估计算法和基于快速傅里叶变换(FFT)信道估计算法的基础上,针对MB-OFDM UWB信号帧结构特征提出了一种基于FFT变换和Hannan-Quinn(HQ)准则的改进算法,即FFT-HQ信道估计算法。该文也提出了一种基于信道估计的自适应均衡算法,利用仿真可以看出此均衡算法在性能上优于传统的基于LS算法调整均衡器系数的方法。     

Design of a Six-Sector Switched Parasitic Planar Array Using the Method of Genetic Algorithms

Switched parasitic planar arrays, as possible implementations of smart antennas, and an efficient method of designing them are presented in this paper. The radiation pattern of an array can be controlled by a digital word, the insertion of which in the antenna feeding circuit achieves electronic beam steering. The 1s and the 0s in the digital word represent the active and short-circuited elements in the array, respectively. The aim of the design is to cover the azimuth plane with six radiation patterns, each one having 3 dB beamwidth equal to 60° and relative sidelobe level not more than –3 dB. The well-known genetic algorithms are used tooptimize the antenna performance, determining the element positions and voltage phase values. This is made feasible by selecting the digital words, among the 2^N–1 available (N-number of elements), which maximize theobjective function containing the pattern requirements of the design. The numerical results presented show a possible application of this idea. An array of seven identical dipoles /2 offers diagrams, with an average 3 dB beamwidth equal to 63°. Relative sidelobe levels lower than –3 dB are obtained. Simulations at different frequencies prove that thearraydesigned here is a narrowband one and its bandwidth is 2.5% of the carrier frequency.     

CDMA系统中智能天线算法分析

介绍智能天线的基本工作原理,分析了CDMA系统中常用的几种智能天线非盲算法,对其在不同运动环境下的仿真结果进行了性能比较。     

Direction-of-Arrival Estimation (DoA) Using Switched Parasitic Planar Arrays and the Method of Genetic Algorithms

An electronically controllable, switched parasitic planar array can be used for the purpose of direction finding. The method proposed in this paper exploits the electronic beam steering, achieved by simply inserting an appropriate digital word in the antenna feeding circuit, to resolve two signals. A genetic algorithm was used to determine the strengths and the angular positions of the incoming signals in the azimuth plane. The results obtained concentrate on wideband signaling in a multipath environment, with and without the presence of noise. The antenna design and the reliability of the direction-finding method are presented. The proposed method is strongly dependent on the type of the receiving antenna (a switched parasitic planar array is superior to a ``uniform' antenna with identical radiation patterns). Increasing the number of radiation patterns available improves the reliability of the method. The reliability of the method slightly deteriorates, as the angular discrimination of the incoming signals becomes smaller, but the results remain quite satisfying.     

On the Degradation of a UWB System Due to a Realistic TX‐RX Antenna System

The ultra‐wideband (UWB) signal radiation process in an antenna is different from that of a narrowband signal. In this paper, we study the degradation of the desired signal component according to the antenna structure and location of a receiver in a bipolar time‐hopping UWB system. And we propose a receiver structure with an adaptive template waveform generator to compensate for the degradation caused by a realistic TX‐RX antenna system.     

密集多径信道下IR-UWB信号同步捕获方法

超宽带(UWB)信号的快速同步捕获是UWB通信系统中的关键问题.本文提出一种分步同步捕获方法,首先采用两种次最优的最大似然估计算法进行粗搜索,然后在粗搜索获得的有限范围内利用最大值阈值检测进行精估计.该方法提高了密集多径信道下极窄脉冲形式UWB信号(IRUWB)的捕获性能,并有效降低了计算复杂度和处理时间.文中还根据IRUWB信号接收特点,从捕获能量的角度定义了捕获概率.通过仿真评估了捕获能量对系统性能的影响,并对算法性能和参数选择进行了分析.     

基于FPGA的横向LMS算法的实现

横向LMS算法是实现自适应数字波束形成的基本方法之一.提出了一种用Matab/Simulink中DSP Builder模块库设计算法模型,然后应用FPGA设计软件Modelsim、QuartusⅡ分析自适应滤波器时钟速度和消耗逻辑单元数的设计方法.实验表明:该方法易于实现、简单可靠.     

改进遗传算法在线阵波束方向图中的应用

通过对传统遗传算法应用在线阵波束方向图中进行分析,从编码方式、变异策略以及选择机制上提出了新的改进策略。改进后的算法减少了编码长度,增加了变异灵活性,更好的保持了种群中个体的多样性,加快了搜索和运算速度和收敛性能。对线阵波束方向图的零陷点生成和旁瓣抑制进行仿真,仿真结果表明改进算法与传统算法相比能明显减少遗传代数,能够更快地找到满意解。