Contribution to the design of filtering and multiplexing RF devices and structures for wireless and satellite communication applications

Abstract

Many investigations on designing electronic devices such as filters, phase shifters and circulators for telecommunication systems are ongoing due to their inevitable role between the transmitter and the receiver in the telecommunication chain. Therefore, studies that investigate the optimization of design of those electronic elements are of great importance. This Thesis work is devoted to the design of filtering and multiplexing radiofrequency (RF) devices and structures for wireless and satellite communication applications. In this work, a deep state of the art on the filtering and multiplexing technologies has been carried out (chapter 2). It states the background of filters, phase shifters and circulators with the introduction of the technologies of the circuits, their synthesis and design techniques, also introducing optimization procedures, such as the gradient based optimization and the genetic algorithm optimization, that reduce the cost and the time of the design process. The main work of this Thesis is focused on RF filters (chapter 3), RF phase shifters (chapter 4) and circulators (chapter 5). The design of RF filters (chapter 3) is mainly focused on tunable waveguide band pass filter using rectangular pins covered by graphene material, allowing the tuning of the center frequency and even the bandwidth of the filter. The design of phase shifter (chapter 4) proposes a novel technique for phase shifters with their synthesis and design techniques based on reflective radio frequency circuit, optimized for frequencies up to 18 GHz. The design process is accompanied by a new optimization method based on genetic algorithms to match any input characters needed. The last device under study is the microstrip circulator (chapter 5). Its design is based on stripline/microstrip topology and some circulator design techniques are proposed. Optimization techniques are also proposed to provide different circulator designs that fulfil demanding requirements in their performance. This document details the Thesis work, identifying preliminary limits on all those device designs, fulfilling the objectives of the Thesis. GOALS (objetivos) The main objectives of the Thesis can be summarized as follows: Objective 1: Design and validation of the design of radiofrequency filters, with special attention to reconfigurable waveguide devices based on the usage of the graphene material as a tuning material, due to the influence of its variation of the resistance on the performance of the bandpass filters caused by the modification of the external voltage applied. Objective 2: Design and validation of the design of radiofrequency phase shifter, with special attention to reconfigurable microstrip devices based on reflective circuits and electronically controllable varactors. Objective 3: Design and validation of the design of radiofrequency circulators based on ferrite materials and reflective circuits with electronically controllable varactors. Objective 4: Implementation of optimization methods for the electromagnetic simulation process, in order to reduce the time and the cost of designing and improving the performance of the devices.