This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided.

Genetic algorithms in engineering electromagnetics

Genetic algorithms are on the rise in electromagnetics as design tools and problem solvers because of their versatility and ability to optimize in complex multimodal search spaces. This paper describes the basic genetic algorithm and recounts its history in the electromagnetics literature. Also, the application of advanced genetic operators to the field of electromagnetics is described, and design results are presented for a number of different applications.

Genetic algorithm optimization applied to electromagnetics: a review

Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

This paper focuses on interacting particle systems methods for solving numerically a class of Feynman-Kac formulae arising in the study of certain parabolic differential equations, physics, biology, evolutionary computing, nonlinear filtering and elsewhere. We have tried to give an “expose” of the mathematical theory that is useful for analyzing the convergence of such genetic-type and particle approximating models including law of large numbers, large deviations principles, fluctuations and empirical process theory as well as semigroup techniques and limit theorems for processes.

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Branching and interacting particle systems. Approximations of Feynman-Kac formulae with applications to non-linear filtering

This paper describes a class of linear thinned arrays with predictable and well-behaved sidelobes. The element placement is based on almost difference sets and the array power pattern is forced to pass through N uniformly-spaced values that, although neither equal nor constant as for difference sets, are a-priori known from the knowledge of the aperture size, the number of active array elements K, and the features of the correlation function. Such a property allows one to predict the bounds of the confidence range of the peak sidelobe of the admissible arrays obtainable through simple shift operations on a binary sequence. The expected peak sidelobe performances turn out to be comparable with those from difference sets, even though obtainable in a wider set of array configurations, and improved in comparison with cut-and-try random-placements.

/pdf/linear-array-thinning-exploiting-almost-difference-sets-4gsbk6k7wp.pdf

Linear Array Thinning Exploiting Almost Difference Sets

The application of modern electromagnetic theory in real world radiation and scattering problems often requires or at least benefits from the use of optimization. This paper discusses a relatively new approach to the electromagnetic optimization problem called the genetic algorithm that can handle the common optimization problem characteristics with relative ease yielding near global maxima in cases that cannot be readily handled by any other optimization method.

Genetic algorithms in electromagnetics

The mobile satellite communications arena has received considerable attention as the next step for personal wireless communications systems. The use of satellites to provide world wide coverage will allow for many new market areas. But the additional opportunities being provided by satellite based personal communications systems has brought additional challenges. One of the new challenges facing the antenna engineers is to provide reasonably sized antennas that deliver acceptable electrical performance for the mobile terminal. This paper reports on work at UCLA to develop personal communication antennas for the big low Earth orbit (Big-LEO) satellite system mobile terminal. The radiators for this system require broad radiation patterns with good circular polarization characteristics, for the particular uplink and downlink bands of 1.61-1.6265 GHz and 2.4835-2.5 GHz respectively.

Quadrifilar-curl antenna for the "Big-LEO" mobile satellite service system

An equivalent magnetic current (EMC) approach has been proposed as an alternative method to the classical modal formulation for computing the far-field pattern of a radiating antenna from planar near-field measurements. The attractiveness of this EMC approach includes the possibility of producing the correct far-field pattern in all regions in front of a planar antenna under test (AUT), a drawback of the classical modal formulation due to its dependence on the Fourier transform and assumptions which must be made about the field outside of the measurement zone, and its adaptability to both irregularly sampled and non-canonical near-field measurement surfaces. A drawback of the EMC approach, however, is its significantly larger computational requirements. A comparison of the EMC and classical modal approaches for near-field to far-field transformation is examined in terms of the resultant far-field patterns. Measurement results for a waveguide-fed slot array using the UCLA bi-polar planar near-field measurement scanner are presented. An implementation of the EMC approach for the bi-polar geometry is described and results obtained using different subsets of the measured bi-polar near-field data are presented and compared to that obtained using the classical modal approach.

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Near-field to far-field transformation of bi-polar measurements by equivalent magnetic current approach

The Wireless Adaptive Microwave Information Systems (WAMIS) program is concerned with the development of adaptive, high speed data communications systems and associated supporting technologies for mobile applications. One of the projects under the umbrella of the WAMIS program is the Hardware Technologies for Adaptive High Bit-Rate Wireless Transceivers currently underway at the University of California, Los Angeles. UCLA's project has among its goals the development of enabling technologies that facilitate the implementation of high data rate, portable digital, wireless data links with data rates up to 60 Mbit/s. The end product of UCLA's effort will be a flexible, robust, digital radio testbed enabling multimedia peer to peer, indoor communication between portable notebook style computers. The testbed radio being developed will incorporate channel coding, frequency hopping, fully adaptive antenna arrays for both transmit and receive, adaptive bit and power allocation, adaptive equalization, adaptive bit rate selection, and various custom RF and IF integrated circuits. The project goals call for the development of antenna array with a minimum operational band of 2.4 to 2.48 GHz that can be interfaced with the project hardware. These requirements imply a printed antenna with a bandwidth that is considerably wider than 2.4-2.48 GHz to allow for manufacturing tolerances and future requirements. This paper reports on an antenna array that has been developed for the UCLA WAMIS project that utilizes a newly developed, broadband, printed circuit antenna element called the tab monopole.

Wideband tab monopole antenna array for wireless adaptive and mobile information systems application

Near-field measurements can be used as diagnostic tools to reconstruct the aperture field distribution of planar array antennas and to locate their possible defective elements. A regularized matrix method for obtaining the individual element excitation of an array antenna from measured near-fields is presented. A computer simulation is performed to evaluate the effect of various near-field parameters such as the measurement distance and the sample spacing on the reconstruction of the excitation. The validity of the approach has been verified using both synthetic and actual measurements data. Good results have been obtained.

Y. Rahmat Samii

Papers

Genetic algorithms in electromagnetics

Quadrifilar-curl antenna for the "Big-LEO" mobile satellite service system

Near-field to far-field transformation of bi-polar measurements by equivalent magnetic current approach

Wideband tab monopole antenna array for wireless adaptive and mobile information systems application

Regularized matrix method for near-field diagnostic techniques of phased array antennas