Narrowband Electromagnetic Coupling Matrix in Coupled-Resonator Microwave Circuits

TL;DR

This paper enhances a novel electromagnetic coupling matrix methodology for coupled-resonator microwave circuits, bridging it with classical theory to provide detailed EM behavior insights for improved circuit design.

Contribution

It introduces a narrowband approximation of the electromagnetic coupling matrix, aligning it with classical coupling matrix theory for better design insights in microwave engineering.

Findings

Reveals electromagnetic coupling among all resonators and ports.

Allows comparison between electromagnetic and classical coupling matrices.

Provides detailed EM behavior including parasitic and leakage couplings.

Abstract

A novel methodology to unleash electromagnetic coupling matrix information in coupled-resonator microwave circuits has been recently proposed [1]. This information is derived from Maxwell's equations and the natural language of electromagnetics is employed. As a result, the coupling matrix coefficients stand only for electromagnetics. In this work, we enhance this approach to reveal valuable design information for microwave engineering, showing the electromagnetic (EM) coupling among all EM resonators and ports. By the same token, the similarities with the well-known classical coupling matrix theory are addressed. We bridge this gap since the classical theory is the preferential language among microwave engineers. Classical coupling matrix theory is a narrowband model for electromagnetics. Thus, we carry out a narrowband approximation in the electromagnetic coupling matrix. This makes it possible to describe the EM coupling coefficients in the same framework as classical circuits. As a result, proper comparison between both coupling matrices is allowed. Finally, both coupling matrix approaches have a common ground, namely, get physical insight and valuable information for design purposes in coupled-resonator microwave circuits. However, only the electromagnetic coupling matrix details all EM behavior, including parasitic and leakage couplings, and the higher-order mode influence in the microwave circuit. Several microwave circuits, such as filters and diplexers, will show the possibilities of this new technique and its relation to classical coupling matrix theory.