Complete S-matrix in a microwave cavity at room temperature

TL;DR

This study experimentally investigates resonance widths in a microwave cavity, distinguishing antenna coupling effects from ohmic losses, and validates a theoretical S-matrix model explaining mode-dependent variations.

Contribution

The paper develops a model to separate antenna coupling effects from ohmic losses and validates it with extensive experimental data in a microwave cavity.

Findings

Identified damping mechanisms: propagation and contour absorption.

Demonstrated mode-dependent resonance width variations.

Validated S-matrix based theory with hundreds of measurements.

Abstract

We experimentally study the widths of resonances in a two-dimensional microwave cavity at room temperature. By developing a model for the coupling antennas, we are able to discriminate their contribution from those of ohmic losses to the broadening of resonances. Concerning ohmic losses, we experimentally put to evidence two mechanisms: damping along propagation and absorption at the contour, the latter being responsible for variations of widths from mode to mode due to its dependence on the spatial distribution of the field at the contour. A theory, based on an S-matrix formalism, is given for these variations. It is successfully validated through measurements of several hundreds of resonances in a rectangular cavity.