IMPROVED VERTICAL COUPLING BETWEEN PRINTED PLANAR TRANSMISSION LINES

Abstract

In microwave devices, an aperture is often used as a radiating antenna element or to direct energy vertically from a feed line on one layer of a circuit to another. Researchers have employed many methods to describe the power transfer between a microstrip feed and a finite slot with little agreement between models. Many of these models are backed with rigorous theory that approach the computational complexity of a full wave solver like the High Frequency Structure Simulator (HFSS) which relies on the computationally intensive finite element method. This thesis proposes a novel approach to analytically model the coupling between a microstrip line feeding a finite slot in a ground plane. It attempts to alleviate the computational intensity of some previous methods of describing coupling between a microstrip and a slot while employing a more rigorous analysis than other simple closed-form analysis approaches. This research analyzes the concept of field reciprocity which has been a common theoretical backing for many existing theories as well as stored energy coupling relations. Beyond this, an equivalent circuit model is developed to describe the coupling at the transition region existing primarily inside the dielectric between a slot aperture in a ground plane and a microstrip feed line. Ultimately, this research provides a fundamental theoretical framework for models of vertical coupling between microstrip lines and finite apertures as well as other types of printed planar feed lines such as strip lines and slot lines.