Optimizing broadband microwave absorbers for applications in the 70-200 GHz range

TL;DR

This paper uses numerical simulations to analyze and optimize broadband microwave absorbers in the 70-200 GHz range, emphasizing the importance of scale size over material properties for achieving high absorption.

Contribution

It demonstrates that absorber scale size relative to wavelength is crucial and compares different impedance taper designs for broadband performance.

Findings

Achieves 99.5-99.9% average absorption across 70-200 GHz

Scale size of 1-4 mm is optimal for performance

Material properties have a weaker impact than geometry

Abstract

We present results of an extensive suite of numerical simulations that probe square-tiled microwave absorber performance as a function of material properties, frequency, geometry, and unit cell size. The work, which probes both specular reflection and total absorption, highlights the critical importance of the absorber scale size relative to the incidence wavelength while suggesting that material properties have a comparatively weaker impact on overall performance. We show that some absorber designs can achieve 99.5-99.9% frequency-averaged absorption across the 70 to 200 GHz range for normal incidence and that low specular reflectance does not necessarily guarantee optimal absorption performance. Our results indicate that exponential, Klopfenstein, and linear impedance tapers provide comparable performance as long as a unit cell size of 1 to 4 mm is chosen. Simulation results are validated against measurements of specular reflectance.