New Elements Concentrated Planar Fractal Antenna Arrays for Celestial Surveillance and Wireless Communications

This research introduces three new fractal array configurations that have superior performance over the well‐known Sierpinski fractal array. These arrays are based on the fractal shapes Dragon, Twig, and a new shape which will be called Flap fractal. Their superiority comes from the low side lobe level and/or the wide angle between the main lobe and the side lobes, which improves the signal‐to‐intersymbol interference and signal‐to‐noise ratio. Their performance is compared to the known array configurations: uniform, random, and Sierpinski fractal arrays.     

Thinning of 2D and 3D Fractal Antenna Arrays with Bounded and Unbounded Fractal Distribution Functions for Celestial Communications

Fractal antenna arrays are geometry‐based thinned arrays having multiband applications. The major challenge of these arrays is their large number of elements at higher expansion factors. This article presents the thinning of fractal antenna arrays while maintaining an appropriate balance between the side lobe level and beam width by using various quantized fractal distribution functions. A 2D square fractal antenna array and 3DSierpinski gasket antenna array are considered in this article to validate the proposed distribution functions. Nearly one third of the antenna elements are thinned in each successive iteration except in the case of a one‐count distribution function. The proposed technique can simplify practical implementation and exhibits better performance for various parameters such as the side lobe level, side lobe angle, and half power beam width than fully populated fractal antenna arrays.     

Synthesis of satellite footprint patterns from rectangular planar array antenna by using swarm‐based optimization algorithms

A pattern synthesis method based on Firefly Algorithm (FA) and Artificial Bee Colony (ABC) optimization has been presented to generate satellite footprint patterns from a rectangular planar array of isotropic antennas by modifying the amplitude, phase, and the state of the array elements. Three cases comprising three different footprints of rectangular, square, and circular boundary are generated from the same array by using two different swarm‐based optimization algorithms FA and ABC. Both the algorithms, following the proposed procedures are able to generate the three different footprint patterns while maintaining a satisfactory lower peak side lobe level and ripple. A comparative analysis has been carried out between FA, ABC, and Genetic Algorithm (GA) for the presented problem in terms of fitness value for the three different cases. The superiority of FA and ABC over GA has been established in terms of finding better solutions for all the three cases of the proposed problem. Copyright © 2013 John Wiley & Sons, Ltd.     

阵列方向图综合的一些方法

介绍了几种常用的阵列方向图综合方法。切比雪夫阵列在指定的副瓣电平下主瓣宽度最窄,在指定的主瓣宽度下副瓣电平最低;相位控制技术通过控制阵列各单元的相位实现波束的指向变化;最后介绍了遗传算法并利用遗传算法优化了8元线阵,将其相对副瓣电平抑制到了-50dB。     

Phased arrays in communication system based on Taguchi‐neural networks

Phased antenna array design is one of the most important electromagnetic optimization problems. This research combined the Taguchi method and artificial intelligence methods, used them as the prediction tool in designing parameters for the communication system, and then constructed a set of the optimal parameter analysis flow and steps. In this paper, we present an application of artificial neural networks in the electromagnetic domain. We particularly look at the multilayer perceptron network, which has been the most used of artificial neural networks architectures both in the electromagnetic domain and in the Taguchi optimization technique and describes the Taguchi method to optimize the excitations elements of the linear array to produce a radiation pattern with minimum side lobe level and null placement control. This paper investigates how the implementation of the signal processing in hardware affects the performance of the adaptive array antenna. The investigation is confined to uplink or receive antenna array only. Results of a prototype of antenna array with feeding values designed using the proposed techniques are also presented. Copyright © 2013 John Wiley & Sons, Ltd.     

超宽带相控阵天线的低副瓣设计

探讨了在超宽带相控阵列天线上实现低副瓣的工程设计方法,提出了采用多阶量化幅相加权的方法实现发射阵和接收阵的低副瓣设计,并在一维线阵上给出了优化设计结果。结果显示该方法具有较好的低副瓣特性及工程应用参考价值。     

任意位置稀布阵天线的遗传优化

任意位置稀布阵通常具有较高的副瓣。为降低副瓣,本文使用遗传算法,提出了一种新的编码方法表示阵元位置。对于一个孔径为50λ,由25个阵元组成的阵列天线,本文得到了较低的副瓣,满足了工程应用的需要。     

基于子阵重叠结构的子阵划分技术研究

对大型阵列进行子阵划分能减少系统控制的路数,子阵级加入时延控制扩展了瞬时带宽。对子阵划分进行重叠排布,提供了窗函数的效果,有效抑制了由子阵划分所引起的过密栅瓣。子阵单元级和子阵级分别进行加权操作,提供了较低的副瓣。     

阵元排布对线性阵列天线的影响分析

线性阵列作为智能天线的一种阵元排布方式,在第三代移动通信中有着特殊的应用。在相同阵元个数的情况下,采用Matlab软件对均匀线阵、约束最小冗余线阵和最优哥伦布线阵的角度分辨能力和主瓣宽度进行仿真比较。仿真结果表明,最优哥伦布线阵可以获得更佳的角度分辨能力和更窄的主瓣宽度,但是会引起方向图旁瓣电平的升高。     

一种新型和差旁瓣抑制阵列天线

针对传统和差阵列天线旁瓣抑制能力的不足,设计了一种应用于二次雷达的新型和差旁瓣抑制阵列天线.该天线主要由前向阵列、后向单元、波束形成网络和互连的射频电缆构成,其中前向阵列和后向单元共同形成差波束.采用遗传算法对各个天线单元的幅度和相位进行优化,使差波束在工作频带内能够覆盖和波束的旁瓣.仿真和测试结果表明:在13.2％相...     

Performance of Smart Antenna Under Different Fading Conditions

Optimizing the current distribution of an evenly spaced antenna array has shown to be an efficient approach for reducing side lobe levels. In this article, the Tchebyscheff distribution-based antenna array synthesis approach is combined with an adaptive signal processing algorithm for beamforming and side lobe level reduction in smart antennas in various fading situations. The performance of smart antennas in uniformly spaced linear, planar, circular, and semi-circular arrays are evaluated. The presence of Rayleigh and Rician channels is examined in the network. The least mean square (LMS) and normalised least mean square (NLMS) algorithms are applied as adaptive algorithms. In fading environments, the NLMS algorithm with Tchebyscheff distribution outperforms than the LMS algorithm with Tchebyscheff distribution, with a side lobe level decrease of 11.23 dB. The lowest side lobe achieved with the NLMS algorithm with Tchebyscheff distribution is???45.59 dB for uniform planar array.

     

Wide‐Band T‐Shaped Microstrip‐Fed Twin‐Slot Array Antenna

A numerical simulation and an experimental implementation of T‐shaped microstrip‐fed printed slot array antenna are presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the finite‐difference time‐domain (FDTD) method. The dependence of design parameters on the bandwidth characteristics is investigated. The measured bandwidth of twin‐slot array antenna is from 1.37 GHz to 2.388 GHz, which is approximately 53.9 % for return loss less than or equal to ‐10 dB. The bandwidth of twin‐slot is about 1.06 % larger than that of single‐slot antenna. The measured results are in good agreement with the FDTD results.     

基于粒子群优化的宽带同心圆环阵型优化方法

同心圆环传声器阵列广泛应用于声成像阵列系统,能有效地抑制干扰并确定声源位置。在限定阵元数量、阵列最大孔径和最小阵元间距等条件下,提出了一种利用粒子群算法设计宽带低旁瓣同心圆环传声器阵列的方法。该方法通过构造一个反映宽带信号在扫描区域内旁瓣水平的适应度函数,以圆环半径和阵元偏转角作为联合优化参数,基于粒子群优化算法实现了阵型的快速优化求解。仿真实验表明,该方法获得的优化阵型在扫描范围内的整体旁瓣水平低于以最高旁瓣级为适应度函数得到的最优阵型,也低于仅优化圆环半径获得的最优阵型,这说明了该优化方法的可行性和有效性。     

数字波束方向图综合技术

数字波束形成技术充分利用了阵列天线所检测到的空间信息,可以获得超分辨率和低副瓣的性能、实现波束扫描和波束赋形等。提出一种基于线性约束最小方差波束形成算法的方向图综合算法,算法通过迭代运算,能够获得需要的方向图形状。算法仿真以降低由24个天线单元组成的均匀圆阵的方向图副瓣为例,通过3次迭代运算,将副瓣电平降至-40dB左右,满足了工程需要,说明算法是有效、可行的。     

Design and performance analysis of side by side,echelon and H‐shaped multiple printed dipole antennas for wireless local area network application

An array of printed dipole antennas for wireless local area network applications is designed and simulated using ads software. In MIMO system, numbers of antenna elements are used in different configuration. This paper presents the simulated results of printed dipole antennas in side by side 4‐element array, echelon and H‐shaped dipole array configurations. The designed antenna is characterized by measuring return loss, radiation pattern, directivity, and gain and also presented the simulated capacity results of different array configurations. The mutual coupling between the dipoles of different orientations is included to make simulation more realistic. Copyright © 2013 John Wiley & Sons, Ltd.     

低副瓣有源相控阵天馈系统中的一体化设计

该文提出低副瓣有源相控阵天馈系统中的一体化设计方法,从几个主要方面阐述如何进行一体化设计,在248元天线阵上试验,实测波瓣的峰值副瓣电平和差波瓣零深均在-31dB以下,当波瓣扫描至60时,其峰值副瓣电平不高于-26.5dB,表明一体化设计的必要性。     

基于压缩感知的均匀圆阵方向不变波束优化方法

针对现有的方向不变波束形成算法在阵元个数确定以后,其波束的主瓣与旁瓣水平无法进一步改善的情形下.本文基于均匀圆阵在现有方向不变波束形成方法的基础上,通过引入压缩感知理论(Compressed Sens-ing,CS),提出了一种可以进一步改善波束主瓣与旁瓣水平的方法.该方法使用压缩感知理论对信号进行压缩采样和稀疏重构,...     

基于迭代FFT算法的平面稀疏阵列优化方法

提出了一种基于迭代FFT算法的优化方法来实现平面稀疏阵列的峰值旁瓣电平优化,并给出了详细的优化步骤.在给定的旁瓣约束条件下,利用阵列因子与阵元激励之间存在的傅里叶变换关系,对不同的初始随机阵元激励分别进行迭代循环,就可以降低稀疏阵列的旁瓣电平.在迭代过程中,根据稀疏率将阵元激励按幅度大小置1置0来完成阵列稀疏.仿真实验...     

Memristive Logic‐in‐Memory Integrated Circuits for Energy‐Efficient Flexible Electronics

A memristive nonvolatile logic‐in‐memory circuit can provide a novel energy‐efficient computing architecture for battery‐powered flexible electronics. However, the cell‐to‐cell interference existing in the memristor crossbar array impedes both the reading process and parallel computing. Here, it is demonstrated that integration of an amorphous In‐Zn‐Sn‐O (a‐IZTO) semiconductor‐based selector (1S) device and a poly(1,3,5‐trivinyl‐1,3,5‐trimethyl cyclotrisiloxane) (pV3D3)‐based memristor (1M) on a flexible substrate can overcome these problems. The developed a‐IZTO‐based selector device, having a Pd/a‐IZTO/Pd structure, exhibits nonlinear current–voltage (I–V) characteristics with outstanding stability against electrical and mechanical stresses. Its underlying conduction mechanism is systematically determined via the temperature‐dependent I–V characteristics. The flexible one‐selector?one‐memristor (1S–1M) array exhibits reliable electrical characteristics and significant leakage current suppression. Furthermore, single‐instruction multiple‐data (SIMD), the foundation of parallel computing, is successfully implemented by performing NOT and NOR gates over multiple rows within the 1S–1M array. The results presented here will pave the way for development of a flexible nonvolatile logic‐in‐memory circuit for energy‐efficient flexible electronics.     

Quantum‐Dot‐Tagged Bioresponsive Hydrogel Suspension Array for Multiplex Label‐Free DNA Detection

A novel hydrogel suspension array, which possesses the joint advantages of quantum‐dot‐encoded technology, bioresponsive hydrogels, and photonic crystal sensors with full multiplexing label‐free DNA detection capability is developed. The microcarriers of the suspension array are quantum‐dot‐tagged DNA‐responsive hydrogel photonic beads. In the case of label‐free DNA detection, specific hybridization of target DNA and the crosslinked single‐stranded DNA in the hydrogel grid will cause hydrogel shrinking, which can be detected as a corresponding blue shift in the Bragg diffraction peak position of the beads that can be used for quantitatively estimating the amount of target DNA. The results of the label‐free DNA detection show that the suspension array has high selectivity and sensitivity with a detection limit of 10^?9 M . This method has the potential to provide low cost, miniaturization, and simple and real‐time monitoring of hybridization reaction platforms for detecting genetic variations and sequencing genes.