天线理论、天线设计、天线方向图

0309697相控阵部分自适应波束形成收发算法[刊]/孙胜贤//电子学报.—2002,30(12).—1755～1758(K)为减少大型相控天线阵的优化唯相权值的计算量,本文提出一种新的相控阵部分自适应波束形成的收发算法。它采用自适应部分地选择控制零点的控制阵元(PA),按照最大信干噪比原则,用部分唯相共轭梯度法计算各个阵元的优化唯相权矢量来减轻干扰的影响。模拟结果表明,当干扰数目小于阵元半数时计算性能有很大提高,同时天线远场模式的主瓣损失、波形变化及干扰方向零点深度与全阵自应相比几乎没有变化。参9     

基于遗传算法的部分自适应波束形成方法

将一种改进的遗传算法用于星载平面阵列天线方向图的实时综合。为了使遗传算法适合实时应用,在唯相自适应阵列的基础上进一步采用了部分阵元和部分比特的自适应波束形成,以降低算法计算量,提高其收敛速度。对基于改进遗传算法的唯相阵列部分阵元自适应波束形成和部分比特自适应波束形成进行了研究。模拟实验结果表明,两种方案都能够在波束“凝视”方向满足一定增益的前提下有效抑制来自旁瓣的强干扰,而且具有比传统唯相算法更快的收敛速度。     

自适应干扰抑制零点展宽算法研究

为了减少杂波、目标回波等因素的影响,自适应副瓣对消方法通常需要在休止期采集干扰样本并完成对消权值计算。当雷达阵面机械转动时,干扰的空间特性会随时间发生变化,导致自适应副瓣对消性能严重下降。针对上述问题,文中提出了一种基于干扰样本特性重构的自适应干扰抑制零点展宽算法。首先,推导了阵面转动引起的干扰空域特性变化 规律;然后,给出了基于休止期采集的干扰样本实现后续时间段内干扰样本的重构方法,使得自适应副瓣对消形成的干扰抑制零点展宽,从而改善接收全程内的干扰抑制效果;最后,通过仿真计算验证了该方法的有效性和稳健性。     

唯相相控阵自适应赋形收发波束形成

在大型窄带自适应相控阵列中,由于实际阵列的非理想化及处理随机分布的干扰时的各种误差,导致控制方向错误,包括控制方向角度错误和载频波动引起的错误,急剧地降低了阵列的性能。本文为减小控制方向错误,考虑在主瓣幅度波形在主瓣方向的导数为零的约束下,按最大信干噪比原则自适应地波束形成,获得优化的唯相权值,采用优化方法中的罚函数法,并结合共轭梯度和拟牛顿法来计算优化的唯相数值权向量。模拟结果表明,在相控阵列的有效自由度下,这种方法能够有效的对抗干扰,同时保持阵列的主瓣波束的幅度波形。     

自适应数字波束形成在大型面阵中的应用

ADBF技术使得雷达能根据干扰特性,自适应地在干扰方向形成零点,以对付强有源干扰.另外,大部分雷达还需要天线具有低或超低副瓣,以提高雷达在强杂波背景下检测目标的能力.随着相控阵雷达阵元数的增多,需要处理的数据量变大,在很短的时间内实现DBF面临很多问题.本文针对大型面阵,讨论了如何利用修正的采样矩阵求逆算法,在有限快拍数内根据干扰环境自适应地形成零点,同时实现天线超低副瓣性能的问题.仿真结果表明了方法的有效性.     

基于虚拟阵叠加原理的阵列抗干扰方法研究

提出了一种基于虚拟阵叠加原理的阵列抗干扰方法。将相控阵列分解成一个主阵列和 N 个虚拟阵列,主阵列采用 Taylor 幅度加权实现低旁瓣电平,并通过相位控制使主波束对准来波方向。虚拟阵列也采用 Taylor 加权,并在主阵列旁瓣上产生 N 个零点,实现阵列的旁瓣对消, 虚拟阵的低旁瓣将减少对阵列主波束的影响,虚拟阵加权后与主阵列叠加最终得到整个阵列抗干扰的幅相权值。文中使用该方法对一个 24 元直线阵进行抗 3 个干扰的设计验证,在 3 个干扰方向实现了小于-100dB 的零点,证实了该方法的有效性。     

发射波束部分阵元置零综合分析

针对选择阵列部分单元控制的情况,分析了发射波束零点形成的两种方式,即部分阵元的幅相加权综合和部分阵元的唯相位综合加权方式。通过对这两种置零综合的算法研究和仿真分析,并从形成零陷的深度及对副瓣扰动等方面,比较了这两种发射波束置零综合方法的性能。     

自适应阵递归干扰置零

本文主要考虑自适应阵列的连续工作状态中的递归干扰置零问题,详细地介绍阵列在外部干扰增加,减少和平移等各种变化情况下自适应权的计算。系统的分析和模拟表明,这种新的方法与原SMI方法相比,优化权值的计算量降低了近似于阵列的阵元数倍,另外还可以降低对对角加载技术的要求。     

合成元三维相控阵天线辐射空间多重控制理论的研究

在接收阵天线中,提高信/噪比,即最大化增益并有效地抑制干扰一直成为研究的中心课题。本文围绕着这个中心,提出了振子型合成元三维相控阵天线辐射空间多重控制理论。它包括:合成元三维阵远区辐射场表达式;合成元在三维空间辐射场型最大方向可控性质;阵辐射场图型多重零点控制的基本关系;在多重零点控制强制条件下,合成元三维相控阵天线方向增益最大化。     

基于空间均衡方法的自适应零点形成

提出空间均衡方法用来消除由天线的机械加工误差和阵面的边缘绕射引起阵元间的幅相误差，对阵列互耦校正后，推导了一种基于空间均衡方法的自适应零点形成算法，该方法极大地提高了阵列的干扰对消性能，实验结果证明了空间均衡方法的优越性。     

Analysis of an over-constrained adaptive array

In antenna arrays, the number of nulls that can be formed independently is equal to or less than the number of array elements minus one. Therefore, if the number of interferences exceeds the number of freedom for pattern synthesis in adaptive arrays, nulls in the radiation pattern can not be steered toward each interference direction. To clarify the behavior of the adaptive array in such an environment, an analysis is made for the case where two interferences are impinging on the two-element directionally constrained adaptive array. As a result, it is proved that the adaptive array acts to reduce the undesired noise power at the array output. However, improvement in output signal-to-noise ratio is insufficient because of the limitation in null formation.     

Spatial correlations in adaptive arrays

A receiving array antenna can steer its main beam toward any direction by adjusting the complex weight in each element. However it cannot always steer one beam and one null toward two prespecified directions simultaneously with a single set of weights. The ability for an array to steer one beam and one or more nulls simultaneously is determined by five factors: 1) element positions, 2) orientations of elements, 3) antenna patterns of elements, 4) polarizations of signals, and 5) directions of the beams and/or nulls. A coefficient is defined, called spatial correlation, which includes these factors and completely characterizes array beam pointing and nulling. Its application to adaptive arrays is demonstrated. The adaptive array performance is dominated by this coefficient and can be improved by properly choosing the first three factors. Several examples on the selection of element placement in adaptive arrays are presented.     

A dense overlapped linear subarray architecture for interference suppressing in small‐scale arrays

Compared to omnidirectional antennas, smart antenna arrays are qualified such advantages as lower interference and better spatial reuse. As developed from large‐scale phased array radar, subarray technology is a key approach to reduce the computational complexity, and a quantity of algorithms for subarray partition and low sidelobe has been studied and applied in radar system. With the development of hardware manufacture, portability and mobility are the trend of devices, which limit the array aperture and number of elements, and the performances are constrained by elements number. This paper proposes a dense overlapped subarray architecture for linear array when elements number is small, to improve the array gain and output signal to interference plus noise ratio, and different weighting mode is employed at element and subarray level for adaptive digital beamforming to obtain special performances. The subarray partition is presented for the linear array, which keeps the spacing at subarray level half wavelength to avoid grating lobes and nulls, and the simulation results demonstrate that the subarray architecture induces better output signal to interference plus noise ratio; meanwhile, the computational amount is reduced. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimum phase-only adaptive nulling

Optimum weighting of adaptive antenna arrays is accomplished by computing the weight vector that maximizes the signal-to-interference-plus-noise ratio (SINR). The optimal weight vector is in general complex with each weight having different magnitudes and phases. However, the design of some antenna arrays facilitates phase-only weighting or phase-only adjustments, whereupon it is desirable to compute the constrained optimal weight vector whose components have fixed magnitudes but variable phases. This constrained optimization problem may be posed as the problem of maximizing the SINR on the space of phase-only vectors. This paper addresses the problem of computing optimal phase-only adaptive weight vectors by exploiting several properties of phasor and matrix algebra. Two new algorithms (the phase-only conjugate gradient and phase-only Newton's method) are introduced. The convergence properties. SINR performance, sidelobe level performance, and nulling performance of these algorithms are demonstrated using simulations and experimental data     

Adaptive null steering beamformer implementation for flexible broad null control

An implementation of adaptive null steering beamformer for flexible broad null control, based on constrained recursive updating of array response zeros and spatial FIR filters, is presented. The design allows the beamformer to form broad nulls and control their widths readily. The new method is of great advantage for sensor array in which the number of array elements is very large compared with the number of interferences the array is designed to suppress. The new beamformer is useful and effective in the environment where both stationary and moving interference signals exist since it can steer both sharp and controlled broad nulls in the appropriate directions. When compared with the conventional LMS covariance matrix taper (CMT) based broad null synthesis method, the proposed beamformer has a faster convergence rate; and compared with the QR-RLS CMT based broad null synthesis method, the proposed method has a lower complexity.     

On grating nulls in adaptive arrays

The effect of element patterns on grating nulls in adaptive arrays is considered. Two simple array models, a two-element and a three-element array with dipole element patterns, are used to study this question. The element patterns are assumed unequal (i.e., the beam maxima point in different directions). It is shown that element patterns greatly affect the occurrence of grating nulls in the array. Unequal element patterns cause extra grating nulls ("sign reversal grating nulls") to occur, in addition to conventional grating nulls. These sign reversal grating nulls can occur even with element spacing less than a half-wavelength. For a two-element array with dipole element patterns, it turns out that grating nulls cannot be avoided if the spacing is greater than a half-wavelength. However, with more than two elements, the situation is not so bleak. An example is given of a three-element array with dipole patterns and one-wavelength spacing in which all grating nulls are eliminated.     

基于压缩感知的自适应数字波束形成算法

该文根据目标在空间的稀疏性,提出了接收端的基于压缩感知理论的自适应数字波束形成算法.在阵元稀布的情况下,用压缩感知的压缩采样理论,恢复出缺失通道的回波信息,然后用恢复的信号做数字波束形成.该算法所形成的波束具有波束旁瓣低,指向误差小,干扰方向零陷深,而且没有栅瓣等优点,波束性能接近满阵时候的波束性能,而且使用该方法减少的阵元数远远大于其他稀布阵方法减少的阵元数.采用蒙特卡罗方法对该方法进行了性能评估,给出了不同信噪比、不同干噪比、不同快拍情况下的计算结果,仿真结果也验证了该算法的正确性.