Design and development of a class of fractal based miniaturized phase shifters

Abstract

Phase shifters are essential components in phased array antennas for wireless and RAdio Detection And Ranging (RADAR) applications. The loaded line, reflective line and switched line phase shifters are the most commonly used phase shifters. Emerging wireless systems have transceivers that require compact and cost effective phase shifters. Physical size and weight of phase shifters are the major issues in mobile and the wireless applications. Hence, miniaturization of phase shifters has become an important objective of Radio Frequency (RF) designer so as to provide portability and affordability in wireless/mobile systems. In the recent past, Defected Ground Structures (DGS), Monolithic Microwave Integrated Circuits (MMIC), Micro Electro Mechanical Systems (MEMS) and fractals have emerged as the possible techniques for miniaturization of RF systems and antennas. The MMIC technology increases the cost and complexity of fabrication while a MEMS based phase shifter is prone to limited life and yield. In this thesis, fractal techniques have been adapted to design and develop miniaturized phase shifters for wireless applications. This thesis presents the design and development of KOCH fractal based single/three bit loaded line phase shifter that can generate small phase shifts. KOCH fractals have lead to reduction in size as well as increase in bandwidth. Tuning of KOCH phase shifter for desired phase shift is easier when compared to the conventional one. Particle Swarm Optimization (PSO) algorithm is one such recently developed evolutionary algorithm which is a population based self-adaptive search based optimization method. In this thesis, particle swarm algorithm is customized for the design of the length of the matching transmission line that are to be altered in a conventional loaded line phase shifter to attain accurate phase convergence in a few iterative tuning. The algorithm and the corresponding simulation results for the single bit loaded line phase shifters are also presented in this thesis. newline newline newline