UCA-RB-MUSIC算法的仿真分析

波达方向估计(DOA)在移动通信中一直具有举足轻重的作用。文章采用均匀圆阵智能天线,首先介绍了一种经典的算法——UCA-RB-MUSIC算法,该算法精度较高,但是运算量大。接着对该算法进行了仿真分析。     

智能天线中的干扰抑制算法研究

介绍了2种用于智能天线中的抑制干扰波束形成算法,与传统的Capon波束形成算法相比,该算法不仅能够在干扰信号方向形成零点,并且还可以在指定方向形成零点,可以更好地提高接收信号的信干比。从稳健性而言,该2种算法要高于传统的Capon波束形成算法。     

干扰抑制技术在通信侦察中的应用

介绍了两种用于智能天线的抑制干扰波束形成算法,与传统的Capon波束形成算法相比,介绍的算法不仅能够在干扰信号方向形成零点,并且还可以在指定方向形成零点,从而更好地提高接收信号的信干比。从稳健性而言,介绍的两种算法要高于传统的Capon波束形成算法。     

几种数字波束零点形成方法的比较

在概述数字波束零点形成加权结构的基础上,给出了幅度相位加权、仅相位加权和混合控制加权三种算法,并进行了比较：幅度相位加权方法形成零点的效果最好,但算法比较复杂;仅相位加权算法运算简单、有利于硬件实现,但只在零点处于特定位置时效果较好;混合控制加权算法实现灵活,但对受控阵元位置要求较高,具有较强的发展潜力。文中最后采用计算机仿真验证了理论分析结果。     

相控阵雷达发射波束自适应零点形成方法研究

对相控阵雷达的发射波束自适应零点形成问题进行了研究.给出了一种适合发射波束自适应零点形成的性能量度,利用Lagrange乘子法得到了最优发射波束的权值矢量.还给出了计算最优权值矢量的算法.仿真结果表明本文的方法是非常有效的.     

基于自适应变换矩阵的数字波束形成方法

与全自适应数字波束形成(ADBF)算法相比,运算量较小的部分ADBF算法性能存在一定程度的下降.为此文中研究了一种基于自适应变换矩阵的数字波束形成方法(T-ADBF).该方法利用对干扰形成的零陷信息,采用零点预处理算法自适应获得新变换矩阵,以形成新的波束指向.性能分析与仿真结果表明,该方法可在运算量少量增加的条件下,不损失系统自由度,接近ADBF算法的性能,具有显著的优越性.     

宽带双频双极化星载赋形反射面天线优化设计

为拓宽星载赋形反射面天线的工作带宽,运用物理光学(PO)、物理绕射理论(PTD)和极小极大值算法(Minimax)对其进行了设计.首先利用PO与PTD相结合的方法来计算天线远场,然后应用Minimax算法对目标函数进行优化来实现宽频带内的波束赋形.优化过程中同时考虑了天线的增益和带宽,并采用归一化的电场来进行构建目标函...     

基于SICL的宽频带毫米波多波束阵列天线设计

为实现第五代移动通信技术(5G)毫米波阵列天线的多波束扫描,提出了一种基于基片集成同轴线(Substrate Integrated Coaxial Line, SICL)的宽频带毫米波多波束阵列天线。多波束阵列天线主要包括基于SICL的宽频带毫米波罗特曼透镜和基于SICL馈电的宽频带磁电偶极子天线,罗特曼透镜腔体采用平板波导结构,移相段采用非色散结构SICL,设计了一种平板波导透镜腔体和SICL移相段的宽频带匹配结构实现宽频带罗特曼透镜。采用SICL耦合馈电的宽频带磁电偶极子天线作为多波束阵列的辐射单元,易于直接与基于SICL的罗特曼透镜连接使用,可实现宽频带波束扫描。基于此设计了一种7个波束端口、9个阵列单元的宽频带多波束阵列天线。仿真结果表明,该罗特曼透镜的-10 dB阻抗带宽约为42%(20.5～31.5 GHz),磁电偶极子天线的-10 dB阻抗带宽约为45%(20.5～32.5 GHz),组成的多波束阵列天线在20.5～31.5 GHz(约42%)频带内可实现±30°的波束扫描,天线结构简单紧凑、剖面低、易集成且能实现宽频带波束扫描,适用于5G毫米波通信。     

数字波束形成技术在智能天线中的应用

研究了波束形成算法在智能天线中的应用,包括直接加权波束形成算法、旁瓣抑制波束形成算法和零点抑制波束形成算法。在研究各种算法的基础上给出了仿真结果,并对比了每一种算法。详细分析了每一种算法的特点及适用条件,为波束形成算法在智能天线中的应用提供了技术参考。     

一种阵列天线快速波束赋形方法

介绍了一种阵列天线快速赋形方法,该方法基于Orchard综合,采用遗传算法对Schelkunoff单位圆零点的位置移动实现波束赋形。波束赋形分为两个步骤:1)根据副瓣电平采用解析法确定初始零点位置;2)以赋形区域内零点径向位移作为自由度,用遗传算法进行赋形区域单目标寻优。相对常见以阵元的幅度相位作为自由度编码的遗传算法赋形,该方法不仅有效避免了副瓣和赋形区的多目标均衡问题,而且算法自由度大幅减少,收敛速度快,能够同时实现较低副瓣电平和赋形区精度要求。通过余割平方赋形和扇形波束两个实例说明该方法的有效性,可以应用于阵列天线快速赋形设计。     

基于插值圓阵的宽带信号二维空间谱估计

在阵列信号处理中,确定信号的波达方向(DOA)需要估计信号的二维(2-D)空间谱。C。Usha Padmini等人(1994)已证明,圆阵用于估计宽带信号的DOA时具有许多好的特性。尤其是在基于圆阵的宽带信号子空间一维DOA估计中,即使不用延迟抽头也不会出现频率-方向模糊。在估计宽带信号的2-D空间谱时,我们发现用不带延迟抽头的圆阵会出现频率-仰角模糊。本文提出了一种用插值圆阵估计宽带信号2-D空间谱的新方法。在估计中,采用大孔径的圆阵(rmin/2)能获得更好的分辨性能和估计稳健性。     

2-D SPATIAL-SPECTRUM ESTIMATION FORWIDE-BAND SOURCES BASED ON INTERPOLATED CIRCULAR ARRAYS

In array signal processing, 2-D spatial-spectrum estimation is required to determine DOA of multiple signals. The circular array of sensors is found to possess several nice properties for DOA estimation of wide-band sources. C. U. Padmini, et al.(1994) had suggested that the frequency-direction ambiguity in azimuth estimation of wide-baud signals received by a uniform linear array (ULA) can be avoided by using a circular array, even without the use of any delay elements. In 2-D spatial-spectrum estimation for wide-band signals, the authors find that it is impossible to avoid the ambiguity in source frequency-elevation angle pairs using a circular array. In this paper, interpolated circular arrays are used to perform 2-D spatial-spectrum estimation for wide-band sources. In the estimation, a large aperture circular array (Υ>λmin/2) is found to possess superior resolution capability and robustness.     

利用空间时频分布实现宽带FM信号2-D到达角估计

提出了一种新的宽带FM信号二维到达角估计方法。本算法将L型天一阵两个臂的空间时频分布矩阵分别进行相干信号子空间平滑处理，并用子窨 方法实现方位和俯仰角估计，计算机仿真证实了算法的有效性。     

Comment on “Constrained Hung-Turner adaptive beamformingalgorithm with additional robustness to wide-band and movingjammers” [and reply]

One of the major claims in the paper of Gershman et al. (see ibid., vol.44, p.361-6, 1996) is that Hung-Turner (1983) projections do not adequately suppress wide-band interference. This statement is only true if too few snapshots are used to estimate the interference subspace. For Hung-Turner projections the use of more snapshots than the rank of the interference is called “averaging over the dimension”. The authors implicitly and wrongly claim that even with “averaging over the dimension”, Hung-Turner projections perform poorly in the presence of wide-band interference. In this comment, we show theoretically and by simulation that Hung-Turner projections adequately suppress wide-band jammers if the number of snapshots is equal to or larger than the rank of the interference. Here, the same sensor array processing model and assumptions are used. Gershman et al. reply that they proposed a new modification of the Hung-Turner (HT) algorithm improving the robustness of this algorithm against wide-band and moving jammers. They also add that their approach can be applied to other adaptive array algorithms as well, and the critical comment contains a misinterpretation of their results and conclusions     

Relative accuracy of several finite-difference time-domain methodsin two and three dimensions

A comparison of the accuracy of several orthogonal-grid finite-difference-time-domain (FDTD) schemes is made in both two and three-dimensions. The relative accuracy is determined from the dispersion error associated with each algorithm and the number of floating-point operations required to obtain a desired accuracy level. In general, in both 2-D and 3-D, fourth-order algorithms are more efficient than second-order schemes in terms of minimizing the number of computations for a given accuracy level. In 2-D, a second-order approach proposed by Z. Chen et al. (1991) is much more accurate than the scheme of K.S. Yee (1966) for a given amount of computation, and can be as efficient as fourth-order algorithms. In 3-D, Yee's algorithm is slightly more efficient than the approach of Chen et al. in terms of operations, but much more efficient in terms of memory requirements     

Conflict detection and resolution in two-dimensional prefix router tables

We show that determining the minimum number of resolve filters that need to be added to a set of two-dimensional (2-D) prefix filters so that the filter set can implement a given policy using the first-matching-rule-in-table tie breaker is NP-hard. Additionally, we develop a fast O(nlogn+s) time, where n is the number of filters and s is the number of conflicts, plane-sweep algorithm to detect and report all pairs of conflicting 2-D prefix filters. The space complexity of our algorithm is O(n). On our test set of 15 2-D filter sets, our algorithm runs between 4 and 17 times as fast as the 2-D trie algorithm of A. Hari et al. (2000) and uses between 1/4th and 1/8th the memory used by the algorithm of Hari et al. On the same test set, our algorithm is between 4 and 27 times as fast as the bit-vector algorithm of Baboescu and Varghese (2002) and uses between 1/205 and 1/6 as much memory. We introduce the notion of an essential resolve filter and develop an efficient algorithm to determine the essential resolve filters of a prefix filter set.     

Quasi-ray Gaussian beam algorithm for short-pulse two-dimensional scattering by moderately rough dielectric interfaces

We consider short-pulse (SP) time-domain (TD) two-dimensional (2-D) scattering by moderately rough interfaces, which separate free space from a slightly lossy dielectric half-space, and are excited by one-dimensional (1-D) SP-TD aperture field distributions. This study extends to the SP-TD in our previous investigation of time-harmonic high frequency 2-D scattering of Gabor-based quasi-ray Gaussian beam fields excited by 1-D aperture field distributions in the presence of moderately rough dielectric interfaces (Galdi et al.). The proposed approach is based on the Kirchhoff physical optics (PO) approximation in conjunction with the Gabor-based quasi-ray narrow-waisted Gaussian pulsed-beam (PB) discretization (Galdi et al.), which is applied to the SP-induced equivalent magnetic surface currents on the interface that establish the TD reflected/transmitted fields. We show that, for well-collimated truncated SP incident fields, the PO-PB synthesis of the reflected/transmitted fields yields an approximate explicit physically appealing, numerically efficient asymptotic algorithm, with well-defined domains of validity based on the problem parameters. An extensive series of numerical experiments verifies the accuracy of our method by comparison with a rigorously-based numerical reference solution, and assesses its computational utility. The algorithm is intended for use as a rapid forward solver in SP-TD inverse scattering and imaging scenarios in the presence of moderately rough dielectric interfaces.     

高分辨率宽带相干信号波达方向的高效估计

本文给出了一种用于多源宽带相干信号波达方向(DOA)估计的快速算法。它是基于信号子空间技术,通过截取中心窄带频段数据并进行空间平滑来获得对方向的高效估计。文中最后通过计算机仿真,与CSM方法进行了比较,验证了本算法的快速、高分辨率等优良性能。     

一种基于行加权的圆阵二维DOA估计改进算法

圆阵可以提供二维DOA估计,在相位模式空间下,UCA—ESPRIT算法具有计算量小、DOA参数自动配对等优点。然而与诸如UCA—RB—MUSIC等算法相比,其均方误差较大。为了保持UCA—ESPRIT算法原有的优点并减小DOA估计的均方误差,将行加权技术引入算法进行改进。     

三维Otsu阈值分割方法的递推算法

一维和二维Otsu法是常用的阈值分割方法,二维Otsu法对含噪图像的分割效果要优于一维Otsu法,但它存在的问题是"对象区域和背景区域上的概率和近似为1"的假设的普适性不够,鉴于此景晓军等人提出了三维Otsu法及其递归算法,使得对低对比度、低信噪比的图像有较好的分割效果.本文指出了景晓军等人给出的递推公式的错误,并进行了修正.鉴于他们给出的递推公式并不是真正意义的递推公式,本文给出了新的递推公式.实验结果表明,本文提出的递推公式进一步减少了运算时间.另外,本文还指出三维Otsu法对于叠加了混合噪声的图像有较好的分割效果.