Efficient modeling of passive electronic devices using the finite-difference time domain method

Abstract

This work pertains to the study of passive electronic devices with fine features, e.g., electronic packages, microstrip antennas and cavity resonators, that are analyzed using the Finite Difference Time Domain (FDTD) algorithm for solving Maxwell's equations. One of the fundamental problems associated with analyzing this class of structures is that accurate modeling of their fine features typically requires a large mesh and an exorbitant amount of computational time. In this thesis, an efficient analysis of such structures is carried out by employing several techniques in conjunction with the conventional FDTD method, which improve its computational efficiency significantly without sacrificing its accuracy. Useful techniques for handling complex structures include non-uniform spacing, subcell modeling, distributed computing and extrapolation.

The advent of high-speed electronic circuits with densely packed interconnects has prompted the need to incorporate high frequency effects into circuit simulators that are capable of accurately modeling transmission delay times and coupling effects. One of the principal advantages of the FDTD scheme is that it can accomplish this task with a single simulation. The time domain response can be processed to extract equivalent circuits that are valid in the high frequency range, up to several gigahertz.

Microstrip antennas are well-suited for use in cellular and mobile satellite applications because of their light weight and small size. However, the conventional patch antenna has a serious degradation of both the axial ratio and the gain as the observation angle moves toward the horizon. Extensive experimentation and numerical modeling have been carried out in this work to obtain wide-angle circular polarization characteristics in microstrip antennas. The highly resonant nature of these devices has been utilized to reduce the computational time. Some of the structures investigated include the dual-band stacked microstrip array and the quarter-wave patch antenna.

Dielectric and cavity resonators find important applications in microwave communication systems. Current trends in the miniaturization of these components place stringent design criteria for the development of compact, high quality, temperature-compensated filters and oscillators. It is demonstrated that the FDTD method can be used to efficiently compute the resonant frequency, quality factor, insertion loss, spurious mode performance and maximum power handling capability in resonators. Furthermore, FDTD enables convenient visualization of the field distribution and provides useful insight into the design of these structures.