基于阵列分解的星载相控阵天线波束成形网络设计

根据"子阵列"理论,对星载阵列相控阵多波束天线的阵元空间和波束空间进行子阵分割,分析天线阵元空间成形系数的复用情况,并结合分布式算法,在阵列分解基础上提出了一种波束成形网络的复用结构,节省了67%以上的资源。最后实现了波束成形网络的试验验证平台,并完成了算法的移植和验证。结果表明,该波束成形网络比常规方法节省了大量资源,并实现了多波束等通量覆盖的设计目标。     

基于毫米波大规模MIMO的分离型子阵列混合波束成形算法

针对大规模MIMO系统中共享型阵列混合波束成形算法结构复杂和耗能较高的问题,提出了基于毫米波大规模MIMO的分离型子阵列混合波束成形算法。该算法采用分步设计的思想,首先根据模拟预编码矩阵的结构特点将天线阵列分解为多个独立的子阵列,并且依次设计每一个天线子阵列的预编码矩阵;然后在模拟预编码矩阵的基础上,采用标准的凸优化算法设计出数字预编码矩阵。仿真结果表明,本文所提算法能够达到较好的频谱效率,同时其能量效率要优于全数字波束成形算法和共享型阵列混合波束成形算法。     

一种高增益宽波束阵元天线

提出一种利用梯形斜面反射结构得到的宽波束阵列单元，该结构形式的天线单元具有较宽的天线波束以及相对较高的天线增益，同时天线极化形式限制较小，且天线波束形状可以根据设计调整。     

旁瓣约束方向不变恒定束宽波束自适应综合

将自适应加权方法应用于波束图的主瓣控制研究,提出了方向不变恒定束宽波束形成算法。在波束图旁瓣区域引入若干虚拟干扰源,自适应调整干扰强度,改变波束形状。以主瓣某一指向的波束宽度为参考,以每次迭代后波束图最低旁瓣峰值与主瓣峰值的差作为下次迭代运算的预设主旁瓣比,在保持主瓣区域宽度不变的情况下,用自适应综合的方法获得不同主瓣指向上的最低均匀旁瓣。将该算法应用于均匀线阵和半球面阵,均在±60°的范围内得到了方向不变恒定束宽波束。研究表明,该算法不仅适用于均匀线列阵,也可用于任意结构阵列。     

Beam shaping with limited amplitude weight values for satellite active phased array antenna

针对星载DBF有源相控阵天线发射波束赋形的实际需要,提出了一种基于有限幅度加权的波束赋形方案。采用双重编码遗传算法实现了该方案。分别采用有限位长度的二进制编码和实数编码对阵列加权矢量的幅度和相位进行编码,使得阵列加权矢量的幅度仅在几个离散的台阶上变化,限制了阵列加权矢量幅度的动态范围,该方案在方向图旁瓣和功率放大器的效率之间取得了折衷,更适合于实际应用。与复数编码遗传算法相比,在保持最优解的精确度的同时,由于幅度维上搜索空间的减小,加快了算法的收敛速度。为了进一步提高算法收敛速度和避免算法“早熟” ,提出了一种基于”物种多样性“选择保留策略,并对算法采用了自适应交叉和变异概率,使算法更有把握得到全局最优或准最优解。     

智能天线MC-CDMA系统中空频联合盲多用户检测算法

提出了智能天线多载波CDMA系统中一种空域和频域联合的盲多用户自适应检测算法,它是将空域波束形成和频域合并检测合二为一,使得检测器在空域和频域两维上同时优化,从而提高了系统的检测性能.对这种空频联合检测算法的误码性能进行了分析,并与先自适应波束形成然后再进行频域合并的分步算法进行了仿真比较,仿真结果表明,提出的空频联合盲多用户自适应检测算法的检测性能优于分步检测算法.     

ADF在相控阵天线阵设计中的应用

针对商用仿真软件ADF在天线阵列中的应用,对矩形多波束平面相控阵天线建立了天线单元模型和25×25模型的仿真,仿真了该阵列的内部天线单元的增益、轴比等性能,仿真结果表明该软件在阵列天线仿真具有很高的使用价值,对相控阵天线的设计应用具有重要的工程指导意义。     

声场重构中消除鬼影和提高重构精度的方法

在利用波束形成算法进行声场重构时，容易出现鬼影现象，给重构声场的准确辨识带来极大困难。在对波束形成算法进行理论推导后，获得麦克风阵列的结构参数与鬼影产生的关系，进而获得消除鬼影的方法；并在此基础上，优化麦克风阵列的布局形式，设计阵列的最大孔径比，可以有效提高重构精度。通过纯音实验和窄带噪声实验，验证了消除鬼影和提高声场重构精度方法的有效性。     

基于遗传算法的单脉冲阵列天线优化

采用遗传算法来优化单脉冲阵列天线的和、差方向图和方向性系数。在天线阵综合时，若不考虑差方向图和方向性系数的影响，所进行的方向图优化仅仅显示出和方向图的特性，对单脉冲阵列天线追踪目标的精度和作用距离没有保证。而在天线阵综合时兼顾和，差方向图以及方向性参数的优化，既可使得天线能发现目标，并使天线能准确对目标实施准确角跟踪，提高雷达的跟踪和作战性能。     

自适应阵列天线波束方向增益特性的研究

介绍了一种适用于时分双工蜂窝移动系统，基于非线性判决反馈均衡器和递归最小平方算法的环形自适应阵列天线，研究了阵列波束对期望信号的增强和对干扰信号的抵消的形成过程，并分析了方向增益的收敛属性与训练序列的关系，计算机仿真结果表明了波束形成与接收信号到达角度之间的联系，发现了波束收敛所需训练序列的最佳长度。     

Investigation of the restrictions on the shape of the radiation pattern of an adaptive antenna array

An algorithm for adapting the radiation pattern of an antenna array to the jamming conditions is described, based on direct inversion of the covariance matrix of the input signals, with a new method of restricting the shape of the radiation pattern for this algorithm. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 44–46, October, 1997.     

Neural network method for direction of arrival estimation with uniform cylindrical microstrip patch array

In this study, a new neural network algorithm is proposed for real-time multiple source tracking problem with cylindrical patch antenna array based on a previously reported Modified Neural Multiple Source Tracking (MN-MUST) algorithm. The proposed algorithm, namely cylindrical microstrip patch array modified neural multiple source tracking (CMN-MUST) algorithm implements MN-MUST algorithm on a cylindrical microstrip patch array structure. CMN-MUST algorithm uses the advantage of directive pattern of microstrip patch elements by considering only a part of array elements for a chosen sector. This reduces neural network sizes and also improves the spatial filtering performance. The proposed algorithm improves MN-MUST algorithm in the sense of accuracy and speed while covering the full azimuth range.     

相关运算在相位干涉仪解模糊中的应用

介绍了相位干涉仪测向的基本原理以及实际测向中存在的相位模糊问题,及长短基线法和立体基线法两种常用的解模糊算法,分析了这两种算法在实际测向应用中的优点和不足。针对上述两种算法存在的问题,提出了一种基于复相关运算的解模糊算法。该算法避开了传统的＂短基线＂解相位模糊的方法,很好地解决了高频测向中对天线阵基线长度的限制。而且,该算法不拘于某一特定形状的天线阵,阵元摆放形式灵活多样,适用于各种用途的测向系统。仿真结果表明,新算法对多种天线阵具有较强适应能力,且在低信噪比下仍具有良好的估计精度,适于硬件实现。     

Study of micromanipulation using stereoscopic microscope

In this paper, we describe a visual feedback system using a stereoscopic microscope that controls a micromanipulator so that a needle may pierce a target with as much length as desired. First, in order to achieve the manipulation at a realistic rate, we proposed a strategy for moving the needle head. Next, we developed an algorithm for prediction of the tip position of the needle head within the target. Before the needle pierces the target, the shape of the needle head is preserved as a reference pattern. After the needle pierces the target, the shape of the needle head within the target is predicted using the reference pattern, and the tip position of the needle head can be detected. Experimental results indicate that the proposed system may be useful in micromanipulation such as microinjection to seeds     

A method for automated digital image-based tracking of delamination fronts in translucent glass fibre-laminated composite materials

A new automated digital image-based method for tracking both the position and shape of the crack front of delaminations in translucent glass fibre-laminated test specimens is proposed. The method is applicable to both fracture toughness tests and fatigue tests. The digital image-based algorithm identifies the newly formed crack area by the change in reflected light and then extracts both the crack front shape and the position. The method is used in a standard double cantilevered beam specimen test setup with the addition of light sources and a camera. The method does not rely on subjective test operator interpretations or calibrations. A reference pattern on the specimen is used to correctly map between the camera coordinate system and the specimen coordinate system, which makes the method insensitive to the camera position and camera or specimen movement during the test. Experimental test examples are provided, which shows that the whole crack front can be tracked with significantly higher accuracy than possible with existing methods.     

Multi-objective sequence optimization of PCB component assembly with GA based on the discrete Fréchet distance

A new mechanism,namely a combination of curve matching method based on the discrete Fréchet distance and evolutionary algorithms,is proposed to solve pick-and-place sequence optimisation problems as a multi-objective optimisation problem. The essence of the mechanism is to accomplish the comparison of objective vectors with curve matching method. The objective vector is mapped into the array of points with a binary mapping operator and the discrete Fréchet distance is utilised to measure the similarity between the reference array of points and the comparison array of points. The genetic algorithm based on the discrete Fréchet distance (FGA) is proposed. To test the new mechanism, together with FGA, three other test algorithms are selected to solve the sequence optimisation problem. The simulation results indicate that FGA outperforms other algorithms. This new mechanism is rational and feasible for multi-objective pick-and-place sequence optimisation problems.     

Correlation processing for correction of phase distortions in subaperture imaging

Ultrasonic subaperture imaging combines synthetic aperture and phased array approaches and permits low-cost systems with improved image quality. In subaperture processing, a large array is synthesized using echo signals collected from a number of receive subapertures by multiple firings of a phased transmit subaperture. Tissue inhomogeneities and displacements in subaperture imaging may cause significant phase distortions on received echo signals. Correlation processing on reference echo signals can be used for correction of the phase distortions, for which the accuracy and robustness are critically limited by the signal correlation. In this study, we explore correlation processing techniques for adaptive subaperture imaging with phase correction for motion and tissue inhomogeneities. The proposed techniques use new subaperture data acquisition schemes to produce reference signal sets with improved signal correlation. The experimental test results were obtained using raw radio frequency (RF) data acquired from two different phantoms with 3.5 MHz, 128-element transducer array. The results show that phase distortions can effectively be compensated by the proposed techniques in real-time adaptive subaperture imaging.     

Direct Three-Dimensional Shape Measurement by Digital Light-in-Flight Holography

A method for direct shape measurement with short laser light pulses and digital holography with a CCD array is proposed. An in-line holographic setup is used in which the reference beam is reflected from a blazed reflection grating, i.e., a Littrow setup. By this method a relatively large optical delay is created between the reference and the object beams even with a small object-reference angle, which is necessary because of the limited resolution of the CCD. The delay varies continuously across one axis of the CCD array. In this way different object sections are reconstructed from different parts of the CCD, which in turn correspond to a certain path length from the object. By putting the sections together, one can evaluate the three-dimensional shape. Theoretical as well as experimental results are presented.     

Optimization of wide-band linear arrays

An optimization method is proposed for linear arrays to be used in ultrasound systems under wide-band operation. A fast algorithm, the threshold accepting, has been utilized to determine the element positions and weight coefficients of a linear array that generates a desired beam pattern. To reduce the computational burden in the optimization procedure, an efficient numerical routine for the beam pattern evaluation has been implemented. We address the optimization problem of both dense and sparse wideband arrays. In the first case, the goal is to minimize the side-lobe energy by varying the element weights; we compare the optimized beam pattern with that obtained with classical shading functions, showing that better results can be achieved with a wide-band optimization. We also consider the optimization of the layout (positions and weights) of a sparse linear array to achieve a desired beam pattern with a fixed or minimum number of array elements. The comparison of the proposed method with a narrow-band optimization algorithm is presented, showing that better performances (about -7 dB further reduction of the side-lobe level) can be achieved with a wide-band sparse array optimization. Further numerical simulations are given, showing that the proposed method yields better results than wideband sparse random arrays and periodic arrays with the same aperture width