Time-domain characterization of microwave circuits.

Abstract

Advances in microwave and millimeter-wave circuit technology in parallel to the advances in computer technology have lead to the development of several sophisticated full-wave time and frequency domain techniques to solve Maxwell's equations in order to obtain the electromagnetic fields and propagation characteristics of these circuits. The goal of this research has been to solve Electromagnetic circuit problems in time domain using efficient numerical techniques. In doing so, the Finite Difference Time Domain (FDTD) based numerical methods have been studied. The first part of this research focuses on using the FDTD technique to characterize novel microwave devices and circuits based on the Coplanar Stripline (CPS). CPS circuits have several applications in wireless communication because of advantages such as excellent propagation, small discontinuity parasitics, efficient use of the wafer area, capability to sustain back metalization, and simplified heat sinking and packaging. In this work, several CPS discontinuities have been characterized and based on these studies, novel CPS filters have been designed and characterized. In addition, minor variants of CPS are investigated for potential applications in microwave circuit integration. For the theoretical characterization of all the CPS circuits, the FDTD technique was used successfully---thus demonstrating the versatility of the FDTD technique in characterizing microwave circuits. However, despite its versatility, simplicity and efficiency, the FDTD technique suffers from serious limitations due to the substantial computation resources required in modeling large-scale problems. The uniform-grid adaptation of this technique (the most widely used because of its simplicity) is a dominant factor contributing to this limitation. In view of the aforementioned disadvantages, the second part of this work focuses on developing an FDTD multigrid scheme using Haar wavelet based Multiresolution in Time Domain (MRTD). The general MRTD scheme using Haar scaling and wavelet functions has been developed here and applied to solve for the Electromagnetic fields in several 2D and 3D microwave circuits. The results obtained are compared with those computed using conventional FDTD technique in order to highlight the benefits of using the MRTD scheme. MRTD technique developed here combines all the advantages of the conventional FDTD scheme with additional benefits, such as, economy in memory and multigrid capability that are offered by Multiresolution Analysis. This leads to a robust time domain tool that has the capability to resolve a number of problems that crop up during the characterization of complex electromagnetic circuits.