Retrodirective arrays for wireless communications

This article reports the recent progress in active and passive retrodirective arrays using phase-conjugation techniques. The arrays presented here are designed for wireless communications in microwave bands and have other features in addition to self-phasing aspects such that they can be applied to practical communication systems. The reliance on purely analog circuitry offers system simplicity and high-speed response. The self-beam-steering feature potentially offers the improvement of communication link gain between an interrogator and a retrodirective array, reducing the burden on transmitting and receiving amplifiers. By implementing a receiving function, it has been demonstrated that retrodirective arrays can also be used in bidirectional communications in either a full or semiduplex manner, initiating a new class of transceiver architecture     

大型非周期相控阵天线协同设计

针对大型非周期相控阵天线的特点,提出一种多学科、多领域协同设计的方法。然后运用该方法指导两个产品天线设计,围绕协同设计的典型流程和几个关键控制点展开论述。在测试阶段实测天线的主要指标,天线1辐射端面平面度≤1.4 mm,栅瓣电平≤-20 dB,天线2辐射端面平面度≤1.1 mm,栅瓣电平≤-18 dB,实测数据与仿真结果吻合,各项指标优于设计输入要求,使用性能良好,验证协同设计方法的有效性。最后指明大型非周期相控阵天线协同设计的进一步研究方向。     

Neural network‐based array synthesis in presence of obstacles

Traditional antenna array synthesis methods are based on the reconstruction of the array factor coefficients or an equivalent current distribution over a surface enclosing the antenna. The coefficients are then used to estimate the amplitude and phase of the feeding voltages that must be applied to the ports of the array in order to generate a radiated field distribution according to a given set of specifications. These approaches consider implicitly that the radiating elements are ideal, without any interaction between them. Coupling effects between the individual radiating elements once inserted in the array might modify their radiation properties and the necessary feeding values for a specified radiated field distribution, affecting significantly to the global behaviour of the array. Neural networks (NN) offer an efficient way to incorporate the real radiating properties and the coupling effects between the elements of an array in the synthesis process without increasing the complexity of the model from the designer's point of view. Once the coupling effects are modelled, they can be used to perform synthesis tasks in presence of any obstacle in a near environment, which can be modelled as a part of the array, with the induced currents established by the coupling effects taken into account in the NN learning procedure. Copyright © 2005 John Wiley & Sons, Ltd.     

基于DSP56F8037的光伏水泵控制系统设计

设计一种基于数字信号处理器DSP56F8037的光伏水泵控制系统。系统主电路DC／DC部分采用结构新颖的推挽正激电路;控制系统采用最大功率点跟踪（TMPPT）技术,提高了光伏阵列的利用率;以具有保护功能的IR2130功率管驱动芯片驱动无刷直流电机,并采用PWM控制技术实现电机高性能运转、全数字控制。实践证明该系统具有体积小、造价低、运行可靠等特点。     

一种基于方向图重构机制的宽带宽视角相控阵天线

本文提出了一款风车形方向图可重构单元及其作为阵元的二维平面宽带宽视角扫描相控阵天线。所提出的单馈方向图可重构单元天线由辐射贴片、直流偏置电路以及宽带人工磁导体(Artificial Magnetic Conductor, AMC)反射面构成。其中,辐射贴片为馈电结构可重构的四个Vivaldi缝隙组成的风车形贴片,它能够通过改变PIN二极管的通断以实现宽带内四个端射方向上的波束切换。此外,将AMC反射面加载于辐射结构的后端,使得最大辐射方向由原来的端射方向调整为准端射方向,这样有利于单元天线组阵后的扫描波束能够覆盖到侧射方向。对该天线单元及其构建的8×8均匀平面相控阵天线进行了仿真与分析。仿真结果显示,所设计的阵列天线同时具备了宽带宽视角二维波束扫描性能,其在5.4 ~ 6.1 GHz的工作频带内可以实现±60°范围内的二维波束扫描。同时,阵列的增益波动小于4.3 dB,并且具有较低的旁瓣电平。     

Wide‐band aperture array using a four‐channel manifold‐type planar multiplexer and digital 2‐D IIR filterbank

Emerging wide‐band communications and spectrum‐sensing systems demand support for multiple electronically scanned beams while maintaining a frequency independent, constant far‐field beam width. Realizing existing phased‐array technology on a digital scale is computationally intensive. Moreover, digitizing wide‐band signals at Nyquist rate requires complex high‐speed analog‐to‐digital converters (ADCs), which is challenging for real developments driven by the current ADC technology. A low‐complexity alternative proposed in this paper is the use of radio‐frequency (RF) channelizers for spectrum division followed by sub‐sampling of the RF sub‐bands, which results in extensive reduction of the necessary ADC operative frequency. The RF‐channelized array signals are directionally filtered using 2‐D digital filterbanks. This mixed‐domain RF/digital aperture array allows sub‐sampling, without utilizing multi‐rate 2‐D systolic arrays, which are difficult to realize in practice. Simulated examples showing 14–19 dB of rejection of wide‐band interference and noise for a processed bandwidth of 1.6 GHz are demonstrated. The sampling rate is 400 MHz. The proposed VLSI hardware uses a single‐phase clock signal of 400 MHz. Prototype hardware realizations and measurement using 65‐nm Xilinx field‐programmable gate arrays, as well as Cadence RTL synthesis results including gate counts, area‐time complexity, and dynamic power consumption for a 45‐nm CMOS circuit operating at B _DC = 1.1 V, are presented. Copyright © 2016 John Wiley & Sons, Ltd.     

基于控制接口芯片的波控系统设计

根据波束控制系统对相控阵雷达天线波束的快速、准确控制要求,提出了一种基于专用可编程T/R控制接口芯片,采用具有地址识别功能的串行分布式波控技术,实现了对某SAR雷达系统的波束控制.介绍了该波控系统的设计原理和具体实现方法,并与常用的几种波控系统进行比较,在满足系统对快速布相要求的同时,有效地减少天线阵面上走线,取得良好...     

Radiation pattern shaping of a mobile base station antenna array using a particle swarm optimization based technique

A new technique of shaping the radiation pattern of an antenna array is presented. The technique aims at finding the appropriate geometry of the antenna array as well as the excitation of the array elements in order to produce a radiation pattern of the desired shape. A suitable optimization procedure is applied using a particle swarm optimization algorithm. The technique has been successfully applied to collinear arrays and seems to be suitable for beam- forming of antenna arrays used by mobile communications base stations.     

A comparison of swarm-based optimization algorithms in linear antenna array synthesis

Today, the design of antenna arrays is very important in providing effective and efficient wireless communication. The purpose of antenna array synthesis is to obtain a radiation pattern with a low side lobe level (SLL) at a desired half power beam width in far-field. The amplitude and position values of the array elements can be optimized to obtain a radiation pattern with suppressed SLLs. In this paper, swarm-based metaheuristic algorithms including particle swarm optimization (PSO), artificial bee colony (ABC), mayfly algorithm (MA) and jellyfish search (JS) are compared to determine the optimal design of linear antenna arrays. Extensive experiments are conducted on designing 10-, 16-, 24- and 32-element linear arrays by determining the amplitude and positions. Experiments are repeated 30 times due to the random nature of swarm-based optimizers, and statistical results show that the performance of the novel algorithms, MA and JS, is better than that of the well-known PSO and ABC methods.

     

2D‐DOA estimation performance using split vertical linear and circular arrays

This paper presents a new approach to reduce the computational complexity in two‐dimensional (2D) matrix pencil (MP) method for direction of arrival (DOA) estimation of plane wave signals using a combination of vertical uniform linear array (VULA) and uniform circular array (UCA). By applying phase mode excitation based beamforming to the UCA, we can apply the matrix pencil (MP) method to the beamspace data using only a single snapshot. The technique is based on the split array, which is composed of two perpendicular arrays. The vertical uniform linear array used to determine the elevation DOA components is located perpendicularly at the center of the uniform circular array in the horizontal plane used to calculate the azimuth angles. Unlike common planar and circular arrays, this antenna array with its particular geometry requires no pair‐matching between the azimuth and the elevation angle estimation and can also remove the drawbacks of estimation failure problems. Using this particular geometry for the 2D MP method leads to an efficient computational methodology for real‐time implementation on a digital signal processor. The obtained simulation results of the MP method applied to both uncorrelated and correlated narrow‐band sources in the presence of white noise show good performance estimation. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于SIW的宽角度波束扫描CPW-CTS天线阵设计

本文基于基片集成波导(substrate integrated waveguide,SIW)提出了一种具有宽扫描角度的连续横向枝节(continuous transverse stub,CTS)频扫天线阵.沿纵向周期排列在共面波导馈线(coplanar waveguide,CPW)上的SIW结构CTS阵列向空间辐射电磁波.提出一种新型宽带CPW慢波结构作为天线阵的馈线,用以增大相邻天线单元之间的相位差,在8.6～13.7 GHz频带内,相位变化范围在89.3°～-83.3°,从而使天线阵主波束随频率实现大范围扫描.为了减少天线阵的后向辐射,在其背面1/4波长处加反射板.设计了一个4元SIW结构CPW CTS天线阵,利用全波仿真软件HFSS进行了分析.结果表明,在8.6～14 GHz频带内天线阵反射系数小于-10 dB,随频率增大实现E面-40°～56°的扫描,在各方向上的最大增益在9.8～12.3 dBi.     

三角格栅排列相控阵天线近场特性研究

为了掌握相控阵天线近场辐射特点,根据波束形成原理,提出了三角格栅相控阵天线辐射近场的数学模型,并进行了仿真验证。计算结果与仿真结果相比,相控阵天线主波束上场强幅度最大偏差约1dB,吻合较好。利用该模型对相控阵天线的电场近场分布特点进行了分析。在近场未形成主波束的区域,波束存在多个波峰和波谷;该区域内法线上场强出现极大值时发射方向在指向各观察点的方向附近徘徊。随着距离增大,波峰和波谷聚拢,波束宽度逐渐收窄;发射方向的徘徊区间慢慢变小,形成主波束后发射方向与实际波束指向一致。所得结论同样适用于矩形格栅相控阵天线。研究结果为相控阵天线的电磁兼容设计、辐射近场测量提供了理论依据和指导。     

A SOFTWARE TOOL FOR ACTIVE ANTENNA ARRAY DYNAMICAL EVALUATION

This paper describes a modelling strategy and a software tool for simulating the dynamical behaviour of an active antenna array. The array consists of active radiating elements placed in a chain, i.e. a collinear array arrangement. To assist modelling of the active antenna array a macro model has been used to represent each of the radiating elements in the array. This simplifies analysis and allows dynamical performance to be efficiently computed, the resulting dynamical behaviour of the array being presented as an animated visualization. A computer program is presented which can simulate the active array in the time domain so that various characteristics, such as mode formation and spacial coupling effects, can be observed. Experimental validation is given in order to justify the mode formation predictions of the simulator. © 1997 John Wiley & Sons, Ltd.     

Surface micromachined segmented mirrors for adaptive optics

This paper presents recent results for aberration correction and beam steering experiments using polysilicon surface micromachined piston micromirror arrays. Microfabricated deformable mirrors offer a substantial cost reduction for adaptive optic systems. In addition to the reduced mirror cost, microfabricated mirrors typically require low control voltages (less than 30 V), thus eliminating high-voltage amplifiers. The greatly reduced cost per channel of adaptive optic systems employing microfabricated deformable mirrors promise high-order aberration correction at low cost. Arrays of piston micromirrors with 128 active elements were tested. Mirror elements are on a 203-μm 12×12 square grid (with 16 inactive elements, four in each corner of the array). The overall array size is 2.4 mm square. The arrays were fabricated in a commercially available surface micromachining process. The cost per mirror array in this prototyping process is less than $200. Experimental results are presented for a hybrid correcting element comprised of a lenslet array and piston micromirror array, and for a piston micromirror array only. Also presented is a novel digital deflection micromirror that requires no digital to analog converters, further reducing the cost of adaptive optics systems     

DBF天线的近场测量与模拟分析

数字波束形成（DBF,Digital Beam Forming）是现代阵列天线系统的关键技术,然而传统的近场天线测量系统与DBF天线的数字接口并不兼容。本文在论述数字波束形成原理的基础上介绍了一种DBF天线近场测量系统。通过对一维DBF天线的近场测量模拟,由近场平面波综合技术得到远场方向图。所得结果与DBF阵列天线远场方向图相比较,可以看出两种方法得到的远场方向图具有良好的一致性。该方法避免了大量探头的使用,克服了探头间的耦合问题。     

基于阵列信号处理的变压器内局部放电源多目标定位方法

提出了一种运用阵列信号处理技术实现变压器内多个放电源同时定位的新方法,该方法在变压器内壁安装两个超声波传感器阵列,通过传感器阵列接收目标空间辐射的超声波信号,应用阵列信号处理技术中的空间谱估计理论分析阵列传感器所接收信号的特征信息(信号源数、传播方向),并完成放电源数的估计、放电源方向的估计和放电源距离的计算,进而实现局部放电的多目标定位。仿真结果表明,该方法具有良好的分辨力和估计精度,能有效估计出变压器内多个放电点的空间位置。     

Shaped patterns synthesis in time-modulated antenna arrays with static uniform amplitude and phase excitations

A novel approach for the synthesis of shaped beam patterns in time-modulated antenna arrays (TMAAs) with static uniform amplitude and phase excitations is proposed in this paper. Based on the sideband radiation in TMAAs, shaped beam patterns can be realized by only controlling the switch-on time sequences of the TMAAs. Differential evolution (DE) algorithm is adopted to optimize the time modulation parameters to obtain the desired flat-top and cosecant-squared beams and to suppress the sidelobe levels (SLLs). Simulation results of a time-modulated linear array (TMLA) and a time-modulated semicircular array (TMSA) demonstrate the effectiveness of the proposed approach for the synthesis of shaped beam patterns from TMAAs.     

基于FPGA的雷达天线方位角信号的模拟系统

为满足天线离线状态下的雷达测试需求,设计开发一种基于 FPGA 的雷达天线方位角信号的模拟系统。雷达天线方位角信号的模拟对雷达信号处理机性能的测试显得尤为重要,设计以伺服控制输出的 PWM信号、电机转动方向控制信号和制动信号作为输入参数,计算出雷达天线的方位角位置,并转换为光电编码传感器的脉冲信号输出给雷达信号处理机。该模拟系统具有输入输出信号属性与雷达天线单元一致、易实现等优点,并已应用于某型雷达测试系统,实践证明效果良好。     

Partial discharge location in power transformers using wideband RF detection

This paper presents a method for partial discharge (PD) source location in power transformers based on detecting electromagnetic (EM) radiation emitted from PD. The key problem of PD location by EM waves is the difficulty in getting the accurate time arrivals of the signals from the source to multiple sensors. Several measures are taken to improve the time arrival resolution. Firstly, a measuring frequency band (1 GHz-5 GHz) within RF band is proposed to accurately pick up the fast rise time of the signals. Secondly, an antenna array with diamond-shaped configuration is designed to improve the correlation coefficient of the waveforms from multiple sensors. Thirdly, two antenna arrays are proposed to eliminate the influences of the EM wave scattering caused by the iron core. Fourthly, an algorithm is proposed to increase the signal to noise ratio and to measure the time arrivals automatically through cross-correlation and averaging operation. Lastly, a hyperboloid-genetic algorithm is developed to search the PD source. Experiments on a single-phase transformer model were conducted in the laboratory. The tested results proved the validity of the proposed method and showed that the location error in 16 cm, mostly is about several cm     

基于智能天线的超高输电塔变形监测技术

提出了一种基于智能天线、扩频技术的超高输电塔变形测量方案,并对系统的工作原理进行了阐述.方案通过在超高输电塔安装多个无线电信标,利用天线阵列对信标的方位、距离信息进行监测,从而得到超高输电塔的变形量.针对多信标的波达方向估计需求,提出了一种基于平面阵的二维多重信号分类的改进算法,并对算法进行了仿真分析.仿真结果表明,提出的算法可以精确估计所有信标的方位信息,可对超高输电塔的变形以毫米级精度进行实时监测.监测到的变形信息将直接用于评估超高输电塔的健康状况.