基于LMS算法的智能天线自适应波束形成研究

自适应波束形成是智能天线的核心技术,其主要思想是利用自适应算法调整阵列的权向量,将各阵元接收到的信号进行加权求和,把天线阵列形成的波束"导向"到一个方向上,使期望用户信号方向得到最大的增益,并相应地使干扰信号方向得到较低的增益,从而提高系统的性能。本文对智能天线中的自适应波束形成进行研究,运用MATLAB软件对固定步长和变步长LMS算法进行计算机仿真实验。仿真结果表明,基于LMS算法的自适应波束形成器能够形成符合要求的波束图,变步长的LMS算法均方误差收敛效果较好,收敛速度更快,具有较强的实用性。     

基于CMA算法的智能天线自适应波束形成研究

自适应波束形成是智能天线的核心技术,其主要思想是利用自适应算法调整阵列的权向量,将各阵元接收到的信号进行加权求和,把天线阵列形成的波束“导向”到特定方向上。本文介绍了恒模算法（CMA）和最小二乘恒模算法（LS—CMA）两种盲波束形成算法并运用Matlab软件对两种算法进行仿真分析,仿真结果表明,LS—CMA具有更快的收敛速度以及更好的抗干扰能力。     

皮智能天线中的LMS自适应波束形成研究

自适应波束形成是智能天线的核心技术,其主要思想是利用自适应算法调整阵列权向量,使天线主瓣指向有用信号,干扰方向对准零陷,尽可能地提高阵列输出所需信号的强度,同时减小干扰信号的强度,从而提高阵列输出的信噪比.运用MATLAB仿真对LMS算法收敛性能进行常规研究,但重点研究了收敛因子、阵元个数、阵元间距等阵列系统因素,以及阵列接收信号过程中两波束夹角对LMS自适应波束形成性能的影响,为进一步优化自适应波束形成的性能奠定了基础.     

均匀圆阵在超宽带系统中的应用研究

介绍了超宽带系统的一种信号模型和均匀圆形天线阵列模型 ,并给出了均匀圆阵的峰值幅度、峰值功率和能量方向图 ;同时 ,还提出了一种快速波束形成算法并进行了计算机仿真 ,仿真结果表明 ,该波束形成算法能实时调整阵列的主波束对准来波的方位角 ,得到信号的最佳接收     

平面天线阵的一种新结构和处理算法

提出一种适用于平面天线阵列的微波和数字处理的联合结构及相应的处理算法.这种结构能够以全数字方式估计波达方向,并能以两种方式进行波束形成.一种是全数字处理方式,另一种是按照阵列单元布局的矩阵处理;用数字微波移相器在俯仰面将天线单元的接收微波信号合成微波波束;采用数字波束形成方式形成最终的波束.并提出了双线法估计波达方向的技术.仿真和测试表明其灵活性和可行性.     

NLMS算法波束形成性能的研究

通过智能天线中的自适应波束形成技术可自动跟踪有用信号和抑制干扰。文中探讨了自适应波束的形成原理,并运用NLMS自适应算法得出了最优权向量,然后通过仿真分析了天线阵列的结构尺寸、入射信号以及信干比SIR对NLMS算法波束形成器性能的影响。     

基于DOA的智能天线下行波束形成方法

首先简要介绍了智能天线的基本概念,然后在阵列等效激励模型的基础上结合信号的波达方向(DOA)和Chebysbev阵列算法提出了一种智能天线下行波束形成方法,最后给出了计算机仿真结果。     

最小二乘恒模算法在阵列天线技术中的应用

介绍一种用于阵列天线，利用信号恒模特性进行自适应波束形成的算法，即最小二乘恒模算法。它通过对阵列天线单元接收信号进行非线性处理，在保持期望目标信号的同时，可在多个干扰方向形成零陷，从而大幅度提高信干噪比(SINR)。文章通过对该算法的仿真对其性能进行了分析，最后阐述了基于该算法的阵列天线应用。     

多径信道中基于盲波束成形的CDMA多用户检测和伪码估计

在分析阵列天线接收的多径CDMA信号的基础上,发掘阵列信号子空间与扩频用户伪码序列的关系,对传统的子空间波束成形器结构做了改进,提出一种新的基于盲波束成形的伪随机码序列盲估计算法。算法采用复独立分量分析法迭代,得到盲波束成形器系数,能在波达方向未知的情况下,估计各个用户的扩频序列。本文同时提出一种基于盲波束形成的异步多径CDMA信号多用户检测算法,可以在未知各个用户扩频码和波达方向的先验知识条件下,完成多径异步CDMA信号的多用户检测。算法由于同时利用了扩频增益和阵列天线分集增益,相比于单天线多用户检测算法性能有所提高。理论分析和仿真结果验证了算法的可行性。      

一种小尺寸极化阵列及其高精度定位波束形成

提出一种偶极子天线单元构成的极化敏感阵列用于全球卫星导航信号的接收,经过阵列信号波束形成后,在抗干扰的同时保留卫星导航信号中载波相位测量值的准确性,可用于基于载波相位测量的高精度差分定位。与传统的圆极化天线阵列相比,该阵列具有阵元构造简单、尺寸小的特点。通过建立极化阵列接收信号模型,分析了天线极化和波束形成算法对卫星导航信号相位的影响,给出了相适应的相位中心稳定的数字波束形成算法。仿真验证了分析的正确性和算法的有效性。     

Principles of space-time array processing for ultrawide-bandimpulse radar and radio communications

The emerging ultrawide-band (UWB) impulse technology has found numerous applications in the commercial as well as the military sector. The rapid technological advances have made it possible to implement (cost-effective, short-range) impulse radar and impulse-radio communication and localization systems. Array beamforming and space-time processing techniques promise further advancement in the operational capabilities of impulse radar and impulse-radio communications to achieve long-range coverage, high capacity and interference-free quality of reception. We introduce a realistic signal model for UWB impulse waveforms and develop the principles of space-time array processing based on the signal model. A space-time resolution function (STRF), a space-frequency distribution function (SFDF) and a monopulse-tracking signal are derived for impulse waveforms received by a self-steering array beamforming system. The directivity peak-power pattern and energy pattern of the beamformer are also derived. Computer plots of the STRF, SFDF and the beam patterns are obtained. The directivity beam patterns of impulse waveforms are sidelobe-free and, therefore, there is no need for sidelobe suppression via amplitude weighting of the array elements. Also, the resolution angle for the beam patterns is derived as a decreasing function of array size and frequency bandwidth. Electronic beamsteering based on slope processing of monopulse waveforms is described     

An Analysis of Interference Mitigation Capability of Low Duty-Cycle UWB Communications in the Presence of Wideband OFDM System

Low duty-cycle (LDC) algorithm is interference mitigation technique, which can reduce the average interference to the existing radio systems by lowering pulse repetition interval or pulse occupation time. In this paper, the coexistence environment between low data rate ultra wideband (UWB) communication system such as wireless sensor network and the existing wideband system using orthogonal frequency division multiplexing (OFDM) such as 4th generation mobile cellular system (4G), worldwide interoperability for microwave access (WiMAX), and field pickup unit (FPU) is considered. In order to analyze the interference mitigation capability of LDC algorithm with impulse based UWB (LDC-UWB) system, the frame error rate (FER) of wideband OFDM system is examined for two types of LDC-UWB system: the signal with random polarity such as binary pole signals and without random polarity such as mono pole signals. We present that LDC algorithm is an efficient interference mitigation technique for low data rate UWB communication via computer simulations regardless of definitions of transmitted energy of UWB communication system, and also that the signal with random polarity is suitable for LDC-UWB system to mitigate interference to the other radio systems. We further investigate the adequate duty-cycle of LDC-UWB system for each definition of transmitted power of UWB communication.     

超宽带无线通信系统的一种新的接收机结构

本文提出了超宽带(UWB)无线通信系统的一种新的接收机结构及其相应的算法。这种接收机可以使用天线阵，然后对脉冲序列相关器的输出进行加权处理，从而增强了通信系统对多用户干扰(MUI)的抑制能力。计算机仿真结果说明，不管是用于脉位调制(PPM)还是脉幅调制(PAM)系统中，这种接收机的性能都优于常规的接收机。     

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。     

基于Hermite函数设计UWB脉冲的算法

由于UWB信号占据的带宽极宽,不可避免地重叠在现有窄带无线通信系统的频段上。为了不干扰其他窄带通信系统,UWB脉冲不仅应具有平坦的频谱且无直流分量,而且其频谱形状也必须满足相应的频谱规划,因此设计满足频谱要求的脉冲是UWB通信系统中一个至关重要的问题。研究了Hermite脉冲的特征,依据其特征提出设计UWB脉冲的算法,用这些脉冲可以构造一个M-ary通信系统。     

Direction of Arrival Estimation of Multiple UWB Signals

This paper deals with the problem of estimation of direction of arrivals (DOA) of a multiple ultra-wideband (UWB) pulse postion modulation signals incident on a smart antenna in the presence of white Gaussian noise. We transform the received signal into frequency domain in order to split the array output into multiple frequency channels. Corresponding frequency channels data of the array is arranged into a model similar to narrowband DOA estimation. Iterative quadratic maximum likelihood algorithm is applied to yield DOA estimates. These separate estimates at different frequencies are combined into a single estimate of DOA for each source in an appropriate manner. The performance of the proposed method is studied via extensive computer simulations. It is seen that the technique can successfully resolve the DOA of the closely-spaced UWB signals.     

一种适用于超宽带脉冲信号检测的改进CUSUM算法

将最快检测技术应用于超宽带脉冲信号检测中,具体采用改进的CUSUM(Cumulative Sum)算法来检测超宽带脉冲信号。首先分析了经过多径信道衰减后的超宽带脉冲信号概率分布特性,进一步提出了适用于超宽带脉冲信号检测的改进CUSUM算法。理论分析和仿真证明了所提改进算法性能优越且实现复杂度低。该算法克服了块检测算法的信噪比门限效应,且具有最优的检测延迟性能,相同虚警限制下其检测性能明显优于能量检测算法。     

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。     

A novel ultra-wideband pulse design algorithm

We present a new algorithm to numerically generate pulses that not only have a short time duration for multiple access, but also meet the power spectral constraint of Federal Communications Commission (FCC) ultra-wideband (UWB) mask. In fact, applying our algorithm to the FCC spectral mask for UWB systems can lead to the design of multiple orthogonal pulses that are compliant. Our algorithm presents a flexible and systematic method for generating UWB pulses that have many advantages over the Gaussian monocycle pulse.