基于混合CSI的非均匀分布随机波束形成方案研究

提出基于混合CSI的非均匀分布随机波束形成方案,通过设定阈值并不断选择匹配波束用户数最多的权重矢量作为发射权重矢量,使波束总是指向用户密度最大的区域,从而更好地利用了多用户系统所带来的分集效应,同时在最大化系统容量方面采用长期相关性CSI进行优化设计,不仅使系统大大减少了反馈量,也使方案在空间相关的广播衰落信道中更加实用有效。     

多波束赋形在非正交多址接入技术中的应用研究

为解决非正交多址接入(NOMA)技术在毫米波Massive MIMO系统中用户的分组受限于基站波束宽度的问题,提出了一种能够产生指向多个方向的波束的波束赋形方案.基于该多波束波束赋形方案,建立了多小区多用户场景下的用户资源分配的数学模型.为降低计算的复杂性,采用两阶段的资源分配算法.在第一阶段中,在给定的功率分配条件下将模型转化为联盟博弈中联盟的生成问题,并提出一种通过迭代确定用户分组和天线单元分配的算法;在第二阶段中,通过将非凸的数学优化问题转化为DC规划问题,提出用户功率分配的算法.仿真结果表明,本文所提多波束波束赋形方案能够有效产生指向多个方向的波束,且所提资源分配算法能够有效提高系统的性能.     

基于斜投影算子的高频雷达窄波束形成方法

波束形成是高频雷达等系统分辨目标方位以及抗干扰的有效手段,常规的波束形成依赖增加阵列孔径实现更窄的波束.提出了一种不受阵列孔径限制的窄波束形成方法,该方法利用斜投影的零相移以及在干扰方向形成的深零陷,通过对宽波束方位内的干扰并行多次抑制,在波束指向周围形成零陷,合成输出窄波束.与传统波束形成相比,本方法具有波束宽度窄、旁瓣抑制比高的特点,尤其是小阵列孔径情况下仍可实现窄波束形成.经高频地波雷达距离-多普勒域实测数据的验证,表明该方法能够实现宽波束内目标的超分辨,并且剔除窄波束以外的电离层杂波,实现了常规波束内的杂波抑制和更为精细的方位分辨.     

方向不变恒定束宽波束图数值综合

该文提出了方向不变恒定束宽波束形成算法。该算法在主瓣控制思想的基础上,以某一指向上的波束主瓣为参考主瓣,用平移参考主瓣的方式构造主瓣位置能随波束指向变化的参考波束,旁瓣高度采用自适应方式调整。在整个观察区域内设置若干虚拟干扰源,用迭代方式不断调整干扰源强度,使任意波束指向上的波束主瓣都与相应的参考波束主瓣吻合,最终获取方向不变恒定束宽波束图。仿真实验表明,该算法能够在主波束指向60范围内形成有效的恒定束宽波束。     

基于相控阵天线的空分复用技术及其容量分析

无人机中继下行方式大多为时分复用（Time Division Multiplexing,TDM）。在TDM以时间资源划分用户的基础上，吸收现有的多波束通信系统的思想，利用相控阵天线技术引入空间资源，提出了一种基于点波束指向逐包快速调整的空分复用(Space Division Multiplexing,SDM)技术。该SDM技术根据数据包的目的地址实时调整点波束天线的指向，在所有波束使用相同频率、相同带宽、相同调制方式的情况下，中心站利用数量较少的波束与大量用户站的通信。在加性高斯白噪声(Additive White Gaussian Noise,AWGN)信道下，通过计算和仿真分析验证了新型的SDM下行方式相对于TDM下行方式能够极大提高下行的信道容量。     

基于凸优化的频率方向二维恒定束宽波束形成技术

针对传统波束的主瓣宽度会随波束指向和信号频率不同而变化,提出了一种基于凸优化的频率方向二维恒定束宽波束形成算法.该算法先采用非线性约束优化实现参考频点的方向不变恒定束宽,然后针对频带内各子带中心频率在每个指向上采用二阶锥约束,实现频率方向的二维恒定束宽.仿真结果表明,该算法能够在主波束指向±40°范围内有效地形成方向不变恒定束宽,同时在每个主波束指向上得到良好的频率不变恒定束宽波束图.     

基于微波光子收发共用真时延网络的相控阵波束合成

针对相控阵雷达宽带宽角波束扫描普遍存在的孔径渡越和波束倾斜的问题,提出了一种基于微波光子技术的相控阵波束形成网络系统,该系统采用收发共用的延时方式,在保证收发波束指向高度一致的同时也减少了系统的设备量。建立了16通道的收发共用的波束扫描系统进行实验验证,实现了X频段范围内的±30°的收发波束扫描,不存在波束倾斜现象,接收和发射波束指向高度一致,结合雷达系统分时收发工作的特点,可有效提升相控阵雷达系统的扫描探测能力。     

基于自适应波束形成的抗干扰跳频通信方案

本文将自适应波束形成技术与跳频通信相结合,提出了一种新的基于空间平滑算法与相位补偿算法的抗相关干扰跳频通信方案.该方案通过采用相位补偿算法,消除了跳频与自适应波束形成相结合时存在的波束指向偏差问题,提高了波束形成的收敛速度.将空间平滑算法应用到波束形成中,有效实现了对跳频通信系统中相关干扰的快速抑制.在强相关干扰环境下...     

基于粒子群优化算法的非均匀子阵波束形成技术

基于粒子群优化算法提出了一种非均匀子阵波束形成方法。首先利用粒子群优化算法实现线阵最优非均匀划分;其次在线阵最优划分的基础上扩展到面阵最优非均匀划分;最后在面阵最优非均匀划分的基础上在期望区域内形成任意指向的波束。该方法既可以在期望区域内形成任意指向波束,又充分发挥了子阵级波束形成的优势。仿真结果表明该方法是有效的。     

一种基于非相邻七馈源组合的波束成形技术

多波束卫星通信系统逐渐向以用户为中心的波束合成体制转变,用户位置的随机性使得目标波束的中心指向应具有任意性,以保证用户服务质量。针对传统的7馈源选择方案波束间干扰较大的问题,设计了一种基于非相邻7馈源组合的馈源选择方案,在满足波束中心指向任意性的同时,通过波束成形算法加权求解,找到均方误差达到最小,实现最佳馈源组合方案,并通过仿真对方案性能进行了分析。     

Null steering in phased arrays by controlling the element positions

Null steering methods usually involve costly and complicated amplitude and/or phase control systems. A technique is presented for null steering based on the element position perturbations. The technique frees the phase shifters to be used solely for steering the main beam toward the direction of the desired signal. It also removes the limitations of the other techniques by independently steering the main beam and the nulls to arbitrary independent directions. This technique is also capable of obtaining sidelobe cancellation and wideband signal rejection     

Phased-array beam steering by multiplex sampling

One approach to phased-array antenna beam forming and steering is to multiplex the element signals into a single channel. Appropriate "sampling" of the resulting multiplexed signal can provide electronically steered and shaped beams. This paper describes four practical system concepts for linear and ring arrays based on this approach and discusses significant interrelationships between the various concepts. For linear arrays of elements, the two alternatives are to frequency or time multiplex the element signals. Frequency multiplexing of the element signals produces time-multiplexed beam output signals, and time multiplexing the element signals produces frequency-multiplexed beam output signals. It is also shown here that appropriate correlation "sampling" may be used with either of these to produce easily one or more continuously and electronically steered signal bandwidth beam outputs. Ring arrays of elements may be multiplexed and "sampled" in a somewhat analogous pair of techniques. It is also pointed out that the beam steering in this case may be visualized as the linear phase steering of a set of linear phase modes into which the signal received at the array may be resolved. Ring array beam forming and steering may thus be directly understood in terms of the previous linear array techniques.     

A robust adaptive array based on signal subspace approach

In this note, we propose a signal subspace approach that improves the performance of a beam steered adaptive array in the presence of steering errors due to look-direction error (LDE) and/or random steering error (RSE). In the method, the degrees of freedom (DOF) are reduced so as not to cancel the desired signal while preserving the optimal characteristic of the array, and thus the weights of the array are determined by a linear combination of the eigenvectors of the signal subspace. The proposed method works as far as the eigen decomposition of the input covariance matrix into signal and noise subspaces is possible. The proposed method improves noticeably the array performance of the beam steered array in the presence of steering errors and provides the optimum array performance in the absence of steering errors     

基于协方差矩阵重构和导向矢量估计的稳健自适应波束形成

实际应用中, 当假定的与真实的期望信号导向矢量之间存在一定误差时, 波束形成器的性能会急剧下降, 特别是当期望信号功率很强的时候.为解决这个问题, 提出了一种新的算法.当信源数小于阵元数时, 干扰加噪声协方差矩阵具有稀疏性.新方法首先利用该特性重构干扰加噪声协方差矩阵并由此得到与干扰导向矢量正交的子空间, 使接收的数据通过该子空间得到只含有期望信号和噪声的混合信号, 然后,对该混合信号基于最大化输出功率原理估计期望信号导向矢量, 最后,把得到的导向矢量和正交子空间来构造阵列加权值.仿真结果表明:该算法分别在假定的期望信号导向矢量存在误差、期望信号很强和低快拍数时仍然具有良好的性能.     

Null steering in phased arrays by controlling the positions of selected elements

A new technique is presented that is capable of steering s in the antenna pattern in the directions of strong interference signals without affecting the main beam. The technique is based on the element position perturbations of selected elements of the antenna array. This technique frees the phase shifters to be used solely for steering the main beam toward the direction of the desired signal. It also freezes the positions of those elements that have insignificant contributions to the s. Our results have shown to be comparable to the results obtained from the method of controlling the positions of all elements.     

基于压缩感知的均匀圆阵方向不变波束优化方法

针对现有的方向不变波束形成算法在阵元个数确定以后,其波束的主瓣与旁瓣水平无法进一步改善的情形下。本文基于均匀圆阵在现有方向不变波束形成方法的基础上,通过引入压缩感知理论（Compressed Sensing,CS）,提出了一种可以进一步改善波束主瓣与旁瓣水平的方法。该方法使用压缩感知理论对信号进行压缩采样和稀疏重构,并通过凸优化中二阶锥规划方法对恢复的信号进行方向不变波束形成,可以在不增加实际阵元数的前提下,增大阵列孔径,得到旁瓣水平更低和主瓣宽度更窄的波束图。仿真结果表明该方法在一定程度上提升了波束形成器的性能,在阵列信号处理方面具有一定的理论与实际意义。      

低信噪比下的信号源个数估计方法

针对低信噪比下信号源个数估计问题,改进基于特征向量与阵列流形正交性的这种目前信号源个数估计效果很好的算法。该改进主要在于引入一个更能去噪的门限准则,结合原来的盲波束形成方法,最后得到一种基于阵列信号处理的信号源个数估计算法。仿真结果证实在低信噪比下,文中所提方法在等功率信号入射时比原方法有效,而且在不等功率信号入射时效果也比原方法好。     

Continuous beam steering and null tracking with a fixed multiple-beam antenna array system

This paper describes how continuous null tracking of a target may be achieved with a fixed pattern multiple-beam forming network with a resulting improvement in tracking accuracy when compared to beam interpolation techniques. Continuous null tracking is accomplished by cascading a hybrid phasing matrix with a beam combining networks called a steering box. The steering box combines three elementary beams in the proper ratio to form a composite sum-and-difference beam which may be continuously steered throughout the coverage angle. The change in the sum-and-difference patterns as a function of steering angle is derived for different steering loci. It is shown how pattern asymmetry may be minimized or sidelobe fall-off rate maximized by the proper choice of a steering locus. Several physical realizations of steering boxes are discussed including the steering box employed in an experimental electronic scanning radar system.     

The effect of a finite distance source on an Applebaum array

The effect of the finite distance of the signal source on the performance of a far-field steering Applebaum type adaptive array is examined. The output signal-to-noise ratio (SNR) is expressed in terms of 1) the distance between the signal and the array center, 2) the input SNR, 3) the element number and locations, and 4) the signal direction. From that expression a rule of thumb is drawn to determine the distance between the signal source and the array center at which the degradation of the output SNR is 1 dB. That distance is in general much larger than the far-field range of a conventional beam forming array.     

Development of Fixed Frequency Beam Steering Wide Band Leaky Wave Cavity Antenna

A complete design of substrate integrated leaky wave cavity antenna for fixed frequency beam steering is presented. The antenna consists of a small rectangular metallic tapered cavity fed by hook-shaped element and covered by the substrate. The steering of the beam in the desired direction is achieved by controlling the taper of the cavity. The beam is scanned at fixed frequency by changing position of the microstrip lines on the substrate. The substrate placed on the cavity resolves the problem of input impedance mismatch. The pertinent features of the antenna are compactness, broadband, and fixed-frequency beam steering capability.