改进型遗传算法在加载天线设计中的运用

遗传算法是一种全新的优化搜索方法，可以用来解决各种复杂的实际问题。针对简单型遗传算法的一些不足之处，介绍了一种改进型的遗传算法，并阐述了其在短波宽带集总加载天线优化设计中的运用。     

Design of multiband microstrip antennas using a genetic algorithm

A genetic algorithm (GA) is used to design patch shapes of microstrip antennas for multiband operations. For dual-band operation, the optimized patches show that arbitrary frequency spacing ranging from 1:1.1 to 1:2 can be achieved. Tri-band and quad-band microstrip shapes are also generated and the resulting designs show good operations at the designated frequencies. All results were verified by laboratory measurements on an FR-4 substrate.     

Circularly polarised printed crossed dipole antennas with broadband axial ratio

A novel printed crossed dipole with broad circular polarisation (CP) is proposed. This dipole is also utilised in 1 times 2 and 2 times 2 array antennas. The proposed dipole can produce CP because of its sequentially rotated configuration. The broadband CP performance is achieved because of a parasitic dipole crossing over the original dipole with a 90deg phase delay line. The experimental results show that single, 1 times 2, and 2 times 2 antennas yield bandwidths of 15.6, 24.5, and 39.2% for 3 dB axial ratio, respectively.     

阵列天线的遗传算法综合

提出了一种基于排序的实数码遗传算法并用于阵列天线的方向图综合。该算法对简单遗传算法的编码方式、选择策略、交叉和变异操作进行了改进,使搜索效率有了很大的提高,有效地避免了早期收敛。在实例设计中体现出优良特性,获得了比有关文献更好的结果。     

基于遗传算法的天线阵方向图零点生成

遗传算法是一种高效的搜索算法.在对遗传算法的发展,基本思想,特点等方面作简要概述的基础上,将该算法应用于唯幅度控制的天线阵方向图零点生成.展示了其广泛的适用性及处理天线阵列综合问题的卓越能力,获得了比已有文献更好的效果.     

混合遗传算法优化设计宽带加载螺旋天线

研究了遗传算法和模拟退火法相结合的方法来快速优化设计宽带加载螺旋天线.采用该算法对加载螺旋天线上的加载集总元件的值、加载位置以及匹配网络参数进行一体化优化设计.采用一种简单有效的方法来快速求解加载元件值和加载位置改变后的阻抗矩阵方程,提高了优化设计的效率.利用该方法成功地设计了两副宽带小型化加载螺旋天线.     

Design of electrically small wire antennas using a pareto genetic algorithm

We report on the use of a genetic algorithm (GA) in the design optimization of electrically small wire antennas, taking into account of bandwidth, efficiency and antenna size. For the antenna configuration, we employ a multisegment wire structure. The Numerical Electromagnetics Code (NEC) is used to predict the performance of each wire structure. To efficiently map out this multiobjective problem, we implement a Pareto GA with the concept of divided range optimization. In our GA implementation, each wire shape is encoded into a binary chromosome. A two-point crossover scheme involving three chromosomes and a geometrical filter are implemented to achieve efficient optimization. An optimal set of designs, trading off bandwidth, efficiency, and antenna size, is generated. Several GA designs are built, measured and compared to the simulation. Physical interpretations of the GA-optimized structures are provided and the results are compared against the well-known fundamental limit for small antennas. Further improvements using other geometrical design freedoms are discussed.     

Design and analysis of planar monopole antennas using a genetic algorithm approach

The application of genetic algorithm (GA) optimization to the design and analysis of planar monopole antennas is presented. GA is first used to optimize the impedance matching bandwidth of two particular planar element shapes, the bow-tie (BT) and reverse bow-tie (RBT). The results of this study indicate that the RBT can achieve a significantly wider bandwidth with a much smaller size than the traditional BT. In a follow-on study, GA is used to generate arbitrarily shaped planar monopole designs, which exhibit improved broadband performance and/or reduced size compared with the RBT. The designs generated by the GA demonstrate a better tradeoff between matching bandwidth and electrical size compared with planar monopole designs previously characterized in the literature. Analysis of results from simulation and measurement are presented, which provide insight into the operation of these antennas as well as the key parameters that lead to improved performance. Finally, a performance bound is generated to relate the bandwidth limitation of planar monopoles to size.     

基于遗传算法的单层宽频带微带天线优化设计

宽带微带天线,尤其是单层宽带天线的设计较为困难.然而U型和E型微带天线提示我们,通过适当去除传统微带天线表面一些特殊位置的金属部分,可以展宽天线带宽.本文阐述了该类天线的工作原理,并详细描述通过采用遗传算法作为优化工具,以及在程序中直接调用IE3D的求解器(MOM)进行计算、提取相关参数进行GA优化的全过程.通过对普通方形贴片微带天线的仿真和实验,我们得到的天线带宽是优化前天线带宽的3倍多,证明了方法的可靠性和高效性.     

用水平天线消除天波干扰的算法研究

天波电台干扰导致探测距离下降是高频地波探海雷达面临的主要问题,虽然用水平天线能够消除天波干扰,但要消除多个干扰需要使用多根水平天线,这在海边有限的场地条件下是不可行的.基于对干扰特性的分析,提出了一种将水平天线的信号两次混频、在时域分段滤波的新算法,可以用较少的水平天线消除多个干扰,理论和仿真证明了算法的有效性,从而为在有限场地条件下,用水平天线消除天波干扰的工程应用提供了实现方案.     

基于一种新的遗传算法的天线方向图综合技术

给出了一种基于实数编码遗传算法的天线方向图综合方法.在遗传算法模型中采用了向下、向上外推和非一致杂交算子等交叉技术,并结合内插、交换等多种技术形成综合交叉方式.该算法克服了已有算法早熟、对初始群体依赖性等缺陷的同时,较大幅度地提高了算法的收敛速度和可靠性;通过在目标函数中加入零陷方差项克服了现有算法零陷不均衡的缺陷.计算机仿真结果表明,与现有算法相比,该方法用于天线方向图综合具有收敛速度快、零陷均衡、可靠等优势.     

Subpicosecond photoconducting dipole antennas

Photoconducting antennas have been demonstrated which are capable of generating and coherently detecting subpicosecond electrical pulses. These antennas, when illuminated with femtosecond optical pulses, radiate electrical pulses which have frequency spectra that extend from <100 GHz to >2 THz. Microscope dipoles measuring 50, 100, and 200 μm have been fabricated and tested. Integrated photoconductors of radiation-damaged silicon-on-sapphire were used both for impulsive current excitation of the transmitting antennas as well as for gating the receiving antennas     

改进遗传算法对高频宽带加载天线的优化设计

按照某高频地波超视距雷达接收天线阵小型化的要求,在4～8MHz频带内,采用一种改进型遗传算法对高频宽带集中加载天线及其宽带匹配网络进行了优化设计.同时根据天线工程与实践,详细分析了集中加载元件值及加载位置扰动对天线电性能的影响,分析表明,优化设计得到的加载参数对优化不十分敏感.     

FDTD/genetic algorithm coupling for antennas optimization

This paper introduces an original theoretical approach for microstrip antennas optimization and design. The purpose method consists in the coupling between a fdtd tool applied to the analysis of antennas and a genetic algorithm for the optimization. A neural network acting as a data base will allow to reduce strongly the computation time. This method will be illustrated on a simple example.     

Accurate modelling of anti-resonant dipole antennas using themethod of moments

The authors demonstrate that the difficulties encountered when modelling anti-resonant antennas are primarily due to the conventional variable gap source model which is commonly employed in thin-wire moment method codes. An alternative source model is introduced, for use in analysing this class of antennas, where the essential feature is that the gap width of the feed region remains fixed. The fixed gap model is compared to the variable gap model for both a half-wave dipole, where the variable gap is still a valid source model, and for a full-wave anti-resonant dipole, where the fixed gap source is shown to be superior to the variable gap model     

Travelling wave microstrip dipole antennas

While it is a common antenna, the unloaded conducting microstrip dipole suffers from a very limited bandwidth because it is a resonant structure supporting a standing wave of current. The authors present the characteristics of a microstrip dipole modified to behave like a travelling wave structure     

Backfire antennas with dipole elements

A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results.     

Broadband calculable dipole reference antennas

A broadband calculable standard dipole antenna has been developed, with an uncertainty in the antenna factor (AF) of better than ±0.15 dB at the resonant frequency, f_res, in the frequency range 30 to 500 MHz and ±0.2 dB in the range 600 MHz to 1 GHz. For broadband operation of the dipole resonant at 60 MHz the uncertainty is ±0.2 dB over a range 0.33 f_res to 1.83 f_res. These uncertainties have been validated by close agreement of the measured insertion loss between dipole antennas above a conducting ground plane, with the loss predicted by analytical and numerical methods. The AF measured by the two-antenna method also agrees with the calculated AF. The technique was applied to reference monopole antennas for which AF was determined to an uncertainty of ±0.2 dB over the frequency range 10-100 MHz. The key achievements are: the construction of a very large and flat ground plane, validation of numerical versus analytical calculations of impedance and effective length of resonant dipoles, excellent agreement between measurements and method-of-moments calculations of the coupling between resonant dipoles, good agreement over a broad bandwidth, careful design of antennas and supports, and precision measurements     

Optimization of log-periodic dipole antennas

It is shown that a log-periodic dipole antenna can be optimized by varying the feed-line characteristic impedance while carrying out swept-frequency far-field and impedance measurements. The minimization of narrow-band anomalies in the measured quantities results in a well-defined optimum characteristic impedance.     

Design of Yagi-Uda antennas using genetic algorithms

A method of using genetic algorithms to optimize the element spacing and lengths of Yagi-Uda antennas is presented. A method of moments code, NEC2, performs the task of evaluating each of the antenna designs generated by the genetic algorithm (GA) during the optimization process. To illustrate the capabilities of the method, the length and spacing of several Yagi-Uda antennas are optimized for various performance characteristics. The results are compared to published results from other optimization techniques and to well-designed equally spaced arrays