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The growing commercial market of Microwave/ Millimeter wave industry over the past decade has led to the explosion of interests and opportunities for the design and development of microwave components.The design of most microwave components requires the use of commercially available electromagnetic (EM) simulation tools for their analysis. In the design process, the simulations are carried out by varying the design parameters until the desired response is obtained. The optimization of design parameters by manual searching is a cumbersome and time consuming process. Soft computing methods such as Genetic Algorithm (GA), Artificial Neural Network (ANN) and Fuzzy Logic (FL) have been widely used by EM researchers for microwave design since last decade. The aim of these methods is to tolerate imprecision, uncertainty, and approximation to achieve robust and low cost solution in a small time frame. Modeling and optimization are essential parts and powerful tools for the microwave/millimeter wave design. This book deals with the development and use of soft computing methods for tackling challenging design problems in the microwave/millimeter wave domain. The aim in the development of these methods is to obtain the design in small time frame while improving the accuracy of the design for a wide range of applications. To achieve this goal, a few diverse design problems of microwave field, representing varied challenges in the design, such as different microstrip antennas, microwave filters, a microstrip-via and also some critical high power components such as nonlinear tapers and RF-windows are considered as case-study design problems. Different design methodologies are developed for these applications. The presents soft computing methods, their review for microwave/millimeter wave design problems and specific case-study problems to infuse better insight and understanding of the subject.

Inhaltsverzeichnis

Frontmatter

1. Introduction

Engineering Design Optimizations
Since the past few decades, engineering design and optimization problems have proved to be promising and important areas of research [1,2]. Many researchers, engineers, and practitioners in academics and industry face difficulties in understanding the role of optimization in engineering design. The goal of optimization is not only to achieve a feasible solution, but also to meet design objectives. In most engineering design applications, the basic goal is to minimize the cost of products/production or maximize the efficiency of production. The goal of the overall design process is also to address the issues such as modeling the process, handling the constraints, forming the objective, and some times handling multiple objectives which may be conflicting in nature. With the advancements in high speed computing technologies, the optimization process has become a part of Computer-Aided Design (CAD) methodology. In a nutshell, optimization is a very powerful tool but it must be applied judiciously in order to achieve efficient solution in feasible time. The contents in the book deals with soft computing methods for the design applications in microwave and millimeter-wave domain.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

2. Soft Computing Methods

Overview
In this chapter, a brief introduction to different soft computing methods, namely, genetic algorithms, particle swarm optimization, bacterial foraging optimization, neural networks and support vector machine has been presented. The overall presentation is separated into sections like evolutionary algorithms, swarm intelligence based algorithms, and methods of learning. Among these methods, genetic algorithms and neural networks have been well explored by microwave researchers, however rest of the techniques are still not much investigated. The rest of the book chapters focuses much on the investigation of these relatively new techniques and their modifications to microwave and millimeter-wave design problems.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

3. Review of Soft Computing Methods for Microwave and Millimeter-Wave Design

Overview
In this chapter, we present a state-of-the-art review on the present use of soft computing methods for the design applications in microwave and millimeter-wave domain [44]. Since long time, the literature on soft computing was confined to the methods such as genetic algorithms, artificial neural network, fuzzy logic, and their variations and hybridizations. During last decade, few other swarm intelligence based algorithms such as particle swarm optimization, ant colony optimization, and bacterial foraging optimization have emerged. Microwave researchers also observe these techniques and try to adopt them for various microwave design applications. In this chapter, a review of microwave design using five soft computing methods namely Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Bacterial Foraging Optimization (BFO), Artificial Neural Network (ANN), and Support Vector Machine (SVM) has been presented. Out of these methods, ANN and GA have been widely exploited by microwave researchers. Though efforts have been made to review related works of all five methods used for microwave design applications, emphasis is given on recent methods, namely, PSO, SVM and BFO. For BFO and SVM, no much has been reported in literature for microwave design.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

4. Design of Microwave Filters Using Modified PSO

Overview
Since last decade due to development of electromagnetic simulators by different developers, it has become a general practice to design microwave/ millimeter-wave components/systems using EM simulation tools. In this process, an initial design is prepared with coarse and approximate analytical and circuit models. This initial design is farther perfected to obtain a final design by making use of suitable EM simulators. However, this procedure is still semi-automated (where EM analysis is obtained with the help of tools, but the adjustment of parameters according to the response is done manually), tedious, time-consuming and chances of getting local minima are very high.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

5. Design of Microstrip Antennas and Other Components

Overview
Since last few decades, commercial growth in the use of microwave products has created necessity for efficient design of components in a small time frame. A Computer Aided Design (CAD) approach is adopted to minimize the time required to obtain an optimized design. In order to use CAD models, the results predicted by them should be consistent with the actual results [92,93]. Due to very small wavelengths involved in microwave design, it requires high precision during the design. Hence, it is not easy to model components of RF/microwave and millimeter-wave domains.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

6. Design of a Nonlinear Taper Using SI Based Algorithms

Overview
Tapered transmission lines (tapers) are common means of transmitting power from one part/device to another part/device in many microwave and millimeter-wave devices. A taper are required to transform the output of a standard waveguide to oversized waveguide components. The design of taper should be carried out in such a way that the characteristic impedances at both the ends match. Two basic types of cross-section tapers are straight taper and variable (nonlinear) taper. In the straight taper, the taper angle is fixed throughout the length and abrupt discontinuities occur at both the ends, while in variable taper the taper angle is smoothly varied along the length of the taper. The advantage of a nonlinear taper is that the conversion of power to unwanted (spurious) modes is very less compared to straight taper [110]. In this chapter, the design and optimization of a nonlinear taper for use in a specific high power gyrotron is presented.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

7. Multiobjective Optimizations for the Design of RF Windows

Overview
High power microwave and millimeter-wave sources such as gyrotrons, klystrons, and other gyro-devices produce huge amount of output power at wavelengths from microwave to millimeter-wave range [110, 127]. Among many components, RF-window is an important component of the output system of these devices. It serves as a barrier between the vacuum side of the device and the output transmission line.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

8. Concluding Remarks

Abstract
In this chapter, the contents presented in the book are summarized, and further readings and experiments are suggested.
N. C. Chauhan, M. V. Kartikeyan, A. Mittal

Backmatter

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