The tripole antenna: An adaptive array with full polarization flexibility

The performance of an adaptive array using three mutually perpendicular dipoles (a "tripole") is studied. A desired signal and an interference signal, each with arbitrary angle of arrival and polarization, are assumed incident on the array. Uncorrelated thermal noise is also assumed present on each element signal. The output desired signal-to-interference-plus-noise ratio (SINR) is computed as a function of the signal arrival angles and polarizations. It is shown that for most angles of arrival and polarizations, the array has an excellent ability to protect a desired signal from interference. Certain special cases where the performance is not good are discussed in detail.     

极化敏感阵列滤波性能分析:完全极化情形

本文研究了完全极化情形下极化敏感阵列滤波性能.期望信号和干扰信号来自任意方向,并且任意极化,推导获得阵列最大输出信号干扰噪声比SINR,它是空间匹配系数和极化匹配系数的函数.与普通阵列相比较,极化敏感阵列不仅可以在空域滤波,而且可以在极化域滤波.当干扰和期望信号到达角差别较大时,阵列通过调整方向特性抑制干扰、增强信号;当干扰信号和期望信号到达角接近时,仍然可以利用它们极化状态的差异提高SINR.对于干扰方来讲,要想获得较好的干扰效果,干扰信号必须要和期望信号具有相同的到达角和极化状态.具体的算例结果验证了理论分析的正确性.     

极化轨道约束下的最优极化（一）

本文针对极化测量过程中干扰和噪声对接收效果的影响，提出一种极化轨道约束下的变极化接收方法，以改卷接收系统的SINR（信号干扰噪声比）。在极化轨道约束下的SINR最大化问题是一个寻求局部最优的问题，本文在任意的信号与干扰极化条件下，解决了任意给定的极化轨道上SINR的最大化问题，并对极化轨迈上最优极化与其他两种最优极化得到的SINR进行了比较。     

极化敏感阵列斜投影滤波性能分析

该文研究了极化敏感阵列采用斜投影滤波和正交投影滤波的输出信干噪比(SINR)特性。推导获得了斜投影滤波与正交投影滤波在理想情况和存在阵列误差时的输出SINR 计算式:理想情况下输出SINR 是信噪比(SNR)、目标与干扰的空域和极化域匹配系数的函数;存在阵列误差情况时输出SINR 受信噪比,干噪比(INR)、目标与干扰的空域-极化域匹配系数及误差扰动量共同影响。分析表明,相比正交投影滤波而言,斜投影滤波的输出SINR没有改善,也不能提高误差稳健性,它们均低于最优输出SINR;正交投影与斜投影输出SINR 相同的成因并不一样,正交投影滤波改变了目标的幅相特性,滤波后目标有损失;斜投影滤波改变了输出噪声的空域-极化域特性,放大了输出噪声的功率。最后通过仿真实验验证了理论分析的正确性。      

通道失配对极化敏感阵列滤波性能的影响

在极化敏感阵列通道失配条件下,建立了极化敏感阵列接收信号误差模型。把通道失配误差分解为阵元极化信息误差和阵列孔径信息误差,给出误差量明确物理解释。在单干扰源情况下,分析了通道失配对极化敏感阵列滤波性能的影响,并给出通道失配条件下,期望信号和干扰信号间的空间匹配系数、极化匹配系数和最大SINR表达式,最后,通过计算机仿真验证了文中结果,并给出有意义的结论。     

Coherent interference suppression with complementally transformedadaptive beamformer

This paper proposes a beamforming scheme for suppressing coherent interference with an array of arbitrary geometry. The scheme first uses estimates of the source directions to construct a transformation, which removes the desired signal while retaining the coherent interference. Optimum beamforming is then performed on the transformed data containing only interference and noise to produce the maximum output signal-to-interference-plus-noise ratio (SINR). Analysis and numerical results demonstrate that the proposed complementally transformed beamformer significantly outperforms the conventional multiply constrained minimum variance (MCMV) beamformers     

Performance analysis of the minimum variance beamformer

We present an analysis of the signal-to-interference-plus-noise ratio (SINR) at the output of the minimum variance beamformer. The analysis is based on the assumption that the signals and noise are Gaussian and that the number of samples is large compared to the array size, and it yields an explicit expression for the SINR in terms of the different parameters affecting the performance, including signal-to-noise ratio (SNR), interference-to-noise ratio (INR), signal-to-interference ratio (SIR), angular separation between the desired signal and the interference, array size and shape, correlation between the desired signal and the interference, and finite sample size     

Performance analysis of the minimum variance beamformer in thepresence of steering vector errors

We present an analysis of the signal-to-interference-plus-noise ratio (SINR) at the output of the minimum variance beamformer in the presence of steering vector errors. The analysis yields an explicit expression for the SINR in terms of the variance of the steering vector errors and the other parameters affecting performance, including signal-to-noise ratio (SNR), interference-to-noise ratio (INR), signal-to-interference ratio (SIR), angular separation between desired signal and interference, array size and shape, correlation between desired signal and interference, and finite sample size     

The maximin algorithm for adaptive arrays and frequency-hopping communications

An algorithm is described for maximizing of the signal-to-interference-plus-noise ratio (SINR) at the output of an adaptive array. The algorithm discriminates between the desired signal and any interference on the basis of the spectral characteristics of frequency-hopping signals. The algorithm maximizes the SINR by maximizing the desired.signal output power while simultaneously minimizing the interference-plus-noise output power. Rapid convergence of the weights to the steady-state values is achieved by the adjustment of the loop gain as a function of the estimated SINR at each iteration. Implementation of the algorithm in conjunction with a frequency-hopping modem is explained. Computer simulation results describe both the steady-state and transient responses of the system under various jamming conditions. The results indicate a rapid dynamic response and the steering of deep nulls over a wide range of the SINR.     

Finite data performance analysis of a sidelobe canceller

The performance of the generalized sidelobe canceller (GSC) is affected by the desired signal (DS) even if all signals are uncorrelated with each other when the DS exists in the received array data with finite snapshot number. Under the condition that the DS is blocked totally in the auxiliary array, a novel expression of the weight vector of the GSC, where the auxiliary array is separated from the main array, is derived for the finite data. Based on the new weight vector, the corresponding expressions of the output signal-to-interference-plus-noise ratio (SINR) can be developed for the case that all signals, including the DS and interference signals, are independent with each other. Then, effects on the SINR for some parameters, including the signal-to-noise ratio, the array antenna number, the direction-of-arrival of the interference signal and the interference-to-noise ratio, are studied, respectively. Some guidelines can thus be obtained for the practical application.

     

Digital filters for attenuating interference arriving from a widerange of angles

Digital filters for the offline multichannel processing of the signals recorded by an array of sensors are derived with the objective of extracting a desired signal arriving from a known direction. Both the desired signal and coherent interference have arbitrary waveforms. Since the direction of arrival of the interference is unknown, the array response to it is treated as a random variable, and the expected value of its squared magnitude is taken as a minimization criterion in order to attenuate the coherent interference. The output power spectrum in response to the additive random sensor noise is taken as a second criterion. A convex combination of both criteria is minimized subject to an all-pass condition for the desired signal. Simulation results are presented showing the tradeoff between attenuating interference and random noise, the effect of the angular separation between the directions of arrival of the desired signal and interference and the effect of the number of sensors of the array on the output of the array filter     

Adaptive compensation for interference-source signals in the radar system with a phased array antenna under completely polarized reception

The algorithms for detecting a known useful signal against the background of intense interferences with an arbitrary law of time modulation multichannel radar system operating in the complete polarization basis is synthesized with the help of an adaptive Bayesian approach. The algorithm makes it possible to identify desired signals under the action of interfering signals even when both types of signals arrive from the same direction.     

信号最优极化滤波及性能分析

研究了信号最优极化滤波问题,以信号干扰噪声比(SINR)为目标函数建立了带非线性约束的优化模型,利用变量代换将其转化为无约束的优化问题,利用极值必要条件将优化问题转化为一元二次方程求根问题,导出了最大SINR和最优接收极化的解析表达式。性能分析表明：信号和干扰极化状态差异越大,滤波性能越好,完全极化干扰容易被抑制,而部分极化干扰效果好。     

基于粒子群优化的数字波束形成算法

波束形成的加权系数求解是一个优化过程,现有算法大多经过多次迭代,计算量大,实现复杂。为降低波束形成算法复杂度,将粒子群优化原理应用于数字波束形成中,提出了基于粒子群优化的自适应数字波束形成算法。该算法将每一组权值作为一个粒子,将阵列加权和的输出信号与干扰噪声比(SINR)作为适应度函数,通过比较各个粒子的适应度值,进行迭代搜索得到最优解。该算法可使天线阵在主波束对准有用信号,同时能有效抑制两个以上的干扰,且对阵列通道误差有较好的稳健性。计算机仿真验证了算法的有效性。     

期望信号功率对MVDR算法性能的影响分析

当接收数据中存在期望信号时,即使是入射信号互相独立, 最小方差无失真响应（minimum variance distortionless response ,MVDR）算法性能都受期望信号功率的影响。在各入射信号相互独立的前提下,本文先是分析了期望信号功率对期望信号输出功率和干扰加噪声输出功率的影响,接着分析了该影响下的输出信干噪比（SINR,signal-to-interference-plus-noise ratio）以及它的收敛速度的变化情况。分析表明,输出SINR在一定范围内是随着期望信号功率的变大而增加,但是当期望信号功率变大到一定程度后,干扰被抑制的强度会随着期望信号功率的变大而减弱,从而导致输出SINR不再随期望信号功率的增大发生变化。SINR的收敛速度也随期望信号功率的增大而变慢。仿真验证了分析结果的有效性。      

Optimal receive antenna polarization in the presence ofinterference and noise

The receive antenna polarization that maximizes the signal-to-interference-plus-noise power ratio (SINR) for an arbitrarily polarized signal is determined in the presence of arbitrarily polarized interference and thermal noise. The derivation makes use of the Poincare sphere representation of polarization and reduces the optimization problem to solution of a single transcendental equation. SINR performance is given in terms of degradation from the polarization matched, noise only case. Finally, a comparison of this optimum-pol strategy, with pol-nulling the interferer and pol-matching the signal is presented. These results provide insight into applying polarization theory to improve signal reception in the presence of interference and thermal noise     

阵列互耦对极化敏感阵列滤波性能的影响

在阵列互耦条件下,给出了极化敏感阵列接收信号模型;并在形式上把互耦误差分解为正交阵元接收因子误差和阵列接收因子误差,分别代表了阵列接收信号极化信息误差和空间信息误差.给出互耦条件下,信号、干扰空间匹配系数、极化匹配系数和最大SINR的数学表达式.在单干扰源情况下,分析了阵列互耦对极化敏感阵列滤波性能的影响.     

A two-sensor array blind beamformer for direct sequence spreadspectrum communications

We present an efficient blind beamformer dedicated to the problem of interference mitigation in direct sequence spread spectrum (DSSS) communication systems using a two-sensor array. A closed-form solution for the blind identification of the communication channel is derived by exploiting the temporal properties of the desired signal and the interference. The optimal beamformer is derived from the maximization of the signal-to-interference and noise ratio (SINR) at the output of the receiver in terms of the blindly estimated channel coefficients. Three structures of the DSSS receiver are presented. One structure consists of the blind beamformer followed by the spread spectrum demodulator. The other two structures consist of the spread spectrum demodulator followed by the blind beamformer. The performance of these structures is discussed in terms of the achieved SINR and the computational cost. Simulation results are provided to illustrate the effectiveness of the proposed blind beamformers in interference excision     

非中心化chi平方伽玛分布杂波模型

韦布尔和对数正态分布雷达杂波模型可描述海杂波的分布,但实现模型不同,且不能对杂波物理成因做出合理解释.这里提出一种非中心化chi平方伽玛分布模型,可精确地模拟海杂波,概率分布特性可与上述两者接近,并且能从物理含义说明杂波产生机理.模拟结果的概率密度分布和功率谱密度估计显示出这种模型具有很好的性能.     

改进的GPS抗干扰自适应天线阵性能研究

文章提出了一种用于GPS接收机的新型抗干扰自适应天线阵,并给出了对其方向图和输出信干噪比的仿真过程.比较了在相同的信号环境时,该天线阵与常用的均匀直线阵、等间隔圆形阵的性能.结果表明,使用该自适应阵可以改善天线阵的方向图,提高输出信号干扰噪声比SINR,增强接收机的抗干扰能力.