Antenna array pattern synthesis via convex optimization

We show that a variety of antenna array pattern synthesis problems can be expressed as convex optimization problems, which can be (numerically) solved with great efficiency by recently developed interior-point methods. The synthesis problems involve arrays with arbitrary geometry and element directivity, constraints on far- and near-field patterns over narrow or broad frequency bandwidth, and some important robustness constraints. We show several numerical simulations for the particular problem of constraining the beampattern level of a simple array for adaptive and broadband arrays     

Antenna pattern synthesis utilizing spherical Bessel functions

Pattern synthesis of linear antennas utilizing the spherical Bessel functions is presented. This leads to antenna current distribution by the Legendre polynomials of the first kind, which are of finite support. Some examples are given to illustrate this procedure     

Antenna synthesis and optimization using generalized characteristicmodes

A set of modes called generalized characteristic modes is described. Previously developed characteristic modes exhibit orthogonality properties over an obstacle surface as well as the complete sphere at infinity. The generalized characteristic modes described here also exhibit orthogonality properties over the obstacle surface, but rather than showing orthogonality over the sphere at infinity, they are orthogonal over any region of space, similar to generalized Inagaki modes. Theories developed for antenna pattern synthesis and directivity optimization using generalized Inagaki modes can be applied in an entirely parallel fashion using generalized characteristic modes. Comparisons are made between generalized characteristic modes and generalized Inagaki modes through three examples     

P pattern recognition based on a probabilistic RAM net usingn-tuple input mapping

A multilayer digital neural network, based on the probabilistic random access memory (pRAM), is used as a P pattern classifier system. This network presents an elaborate implementation of the n-tuple technique, which has mostly been used for pattern recognition (Bledsoe and Browning, 1959). The network's main properties, discrimination and generalisation, are discussed as a function of the pRAM connectivity. Pyramid networks, based on different pRAM connectivities, are simulated using an enhanced version of global reinforcement learning. n-tuple input mapping based on data analysis is proposed. The results show that combining the permuted data-based input mapping with a pRAM net, using different node connectivities through the pyramid layers, can achieve a good balance of the network's properties, when handling a P pattern classification task. Results are presented for the 10 digit recognition problem, which are motivating and very encouraging     

Antenna synthesis and optimization using weighted Inagaki modes

Inagaki modes represent a new modal formalism for problems of radiation and scattering from arbitrary discrete and continuous structures. These modes can be generalized to be orthogonal over any sector of the sphere at infinity, as well as the source region itself. Theory and application of these modes to problems of pattern synthesis and array optimization, including constraints, are presented. Examples are given for a line source, an array of printed dipoles, and a dipole array in free space.     

Antenna selection for MIMO system based on pattern recognition

This paper proposes a novel Multiple-Input Multiple-Output (MIMO) transmission scheme based on Pattern Recognition (PR), which is termed as the PR aided Transmission Antenna Selection MIMO (PR-TAS aided MIMO). As the conventional TAS algorithms need to search all possible legitimate antenna subsets, they may impose some redundant calculations. In order to avoid this problem, we employ some pattern recognition methods to carry out the TAS algorithm in this paper. To be specific, two PR algorithms, namely the K-Nearest Neighbor (KNN) algorithm and the Support Vector Machine (SVM) algorithm, are introduced and redesigned to obtain a TAS with lower complexity but higher efficiency. Moreover, in order to improve the performance of the SVM, we propose a new feature extraction of channel matrix for the TAS. Our simulation results show that the proposed KNN and SVM based PR-TAS algorithms are capable of striking a flexible tradeoff between the complexity and the Bit Error Rate (BER), and the new feature can effectively improve the BER performance compared with the conventional feature extraction method.     

Antenna pattern synthesis in operational environments with electromagnetic compatibility-based constraints

A general linear least squares synthesis technique for antenna arrays is presented that takes account of mutual coupling among array elements and interactions with array's physical surroundings. The technique can be applied to optimize the radiation pattern of arbitrary arrays in their operational environment while simultaneously addressing electromagnetic compatibility based constraints. Examples employing the wire and plate-dielectric (WIPL-D) numerical code are presented to illustrate the approach. Use of this technique with experimental data has also been performed and will be reported in future paper.     

Antenna pattern synthesis using a relaxation method: application to printed antennas

An antenna pattern synthesis method based on a relaxation technique is proposed. The radiation pattern of the elementary source and the interelement spacings are taken into account. Two examples of linear printed arrays are computed: sector pattern and directive broadside pattern.     

Antenna power pattern synthesis using method of successive projections

A general technique for the synthesis of antenna power patterns is presented which does not require the calculation of derivatives. Based on the method of successive projections, it leads to a fast and simple algorithm. An example is presented for a satellite antenna giving hemispheric coverage from a directly radiating horn array.     

基于立体方向图和十字跟踪扫描法校准天线指向

针对明安图射电频谱日像仪（Mingantu spectral radioheliograph，MUSER）天线高指向精度动态跟踪要求，同时为降低非理想因素对复杂系统天线指向测量影响，提出校准天线指向的组合方法.先用网格法测量天线的双圆极化多频率通道立体方向图定性评估系统测量链路状态，后对太阳运行轨道进行十字跟踪扫描测量天线指向偏差，再用最小二乘法拟合获得天线指向模型的8个参数.国家天文台明安图观测基地的2台20 m地平式天线将在MUSER系统观测和校准中起重要作用.对20 m天线跟踪指向进行了校准，指向偏差均方根从12'改善到4.4'，验证了方法的可行性，为类似复杂系统的相关工作提供了借鉴和参考.     

基于改进粒子群算法的天线方向图综合技术

针对基本粒子群算法的早熟收敛、易收敛于局部极值的特点，提出一种改进的粒子群优化算法，采用对全局最佳微扰和惯性权重跳变阈值的设置改善了算法的优化速度和收敛精度。经过对一系列测试函数的计算，证明该方法具有良好的优化效果。最后，给出了该方法应用于阵列天线方向图综合中的模型和仿真实例。     

基于改进粒子群算法的天线方面图综合技术

针对基本粒子群算法的早熟收敛、易收敛于局部极值的特点,提出一种改进的粒子群优化算法,采用对全局最佳微扰和惯性权重跳变阈值的设置改善了算法的优化速度和收敛精度.经过对一系列测试函数的计算,证明该方法具有良好的优化效果.最后,给出了该方法应用于阵列天线方向图综合中的模型和仿真实例.     

一种KLT优化模式下的图像隐写术

针对现有信息安全领域隐写技术存在的感知失真过大和图像源压缩率高造成误差率也高的问题,设计了一种基于KLT(Karhunen-Loeve Transform)优化的图像隐写术。该方法引入KLT算法压缩图像数据,用最低有效位代替加密数据,加上原始像素矩阵获得有效的图像信息。实验结果表明,该方法相比常用的算法在容量上有所提高,信噪比较高,提取到的图像数据失真较小。     

粒子群优化算法用于阵列天线方向图综合设计

粒子群优化算法是基于一群粒子的智能运动而产生的一类随机进化算法,其优点是算法非常利于理解和应用.本文介绍了粒子群算法的原理和流程,研究了如何将这种方法运用于天线阵的方向图综合上,给出了PSO算法在综合阵列方向图的应用实例,表明粒子群算法在天线阵列综合中具有广泛的应用前景.     

基于方向图拓展和FFT的阵列快速综合法

基于阵列方向图自身的周期特性，将方向图近似地拓展至不可见区域，使任意间隔阵列的方向矢量成为空间正交基，以便采用快速傅利叶变换算法，并通过迭代过程中迭代目标方向图的逐次改变，最终实现了阵列方向图的快速综合。数值计算结果和计算量分析表明，和现有方法比较，算法的收敛速度获得了很大的提高。这对于大规模的阵列，其优越性更加明显。     

凸规化法实现多维稀疏阵的方向图综合

本文研究了利用凸规划方法综合稀疏随机阵方向图的问题,采用最大信号干扰加噪声比准则,利用附加的线性约束对旁瓣作进一步控制,将方向图设计问题分别转化为二次规划和二次锥规划形式,再用内点法求解。该方法应用于不同形式的稀疏阵列方向图综合,获得了良好的结果。     

An antenna pattern synthesis technique for spaceborne SARperformance optimization

An antenna pattern design technique for spaceborne synthetic aperture radars (SARs) that optimizes the signal-to-disturbance ratio is presented. It takes into account the ground reflectivity (relative to the transmitted frequency) and the viewing geometry (altitude and off-nadir angle). The technique makes use of the theory of adaptive arrays and takes advantage of a priori knowledge of the ambiguous echo power as a function of the geometry and average ground reflectivity. The optimized antenna weighting turns out to be complex, and asymmetrical patterns are generally obtained for a spaceborne SAR. The technique allows the achievement of better performance compared to the current design values, especially at large off-nadir angles     

基于改进型蚁群算法的阵列天线综合

将蚁群算法应用于优化阵元电流幅度,以实现对阵列天线方向图的综合。并针对传统蚁群算法难以解决电流激励幅度这样的连续变量优化和早熟收敛的问题,提出了一种改进型蚁群算法。该改进型蚁群算法对变量采用不整编码并在寻优过程中采用邻域优化方法,使其既可以对连续变量寻优,又同时改善了算法的优化速度和收敛精度。计算结果表明:该改进型蚁群算法在改变阵元激励幅度的方向图综合问题上取得比相关文献更好的结果。