Broadband time-modulated absorber beyond the Bode-Fano limit by energy trapping

TL;DR

This paper introduces a novel broadband absorber that surpasses the Bode-Fano limit by employing a time-modulated energy trap, demonstrated through circuit modeling and practical PCB prototypes.

Contribution

It presents a new method using time-modulated switches/diodes to exceed the traditional Bode-Fano bandwidth-efficiency trade-off in broadband absorbers.

Findings

Prototype achieves a Bode-Fano integral greater than one.

Demonstrates practical implementation with a PCB design.

Validates concept through circuit modeling and measurements.

Abstract

Wide-band absorption is a popular topic in microwave engineering to protect sensitive devices against broadband sources. However, the Bode-Fano criterion defines the trade-off between bandwidth and efficiency for all passive, linear, time-invariant systems. In this letter, we propose a broadband absorber beyond the Bode-Fano limit by creating an energy trap using time-modulated switch/diodes. This work starts with an ideal circuit model to prove the concept, followed by two EM realizations - a freuqnecy selective surface (FSS) approach for general bandwidth broadening and a low-profile PCB design. The prototype of the latter is built and measured, demonstrating a Bode-Fano integral larger than one. This approach paves a way to many practical ultra-wide band absorber designs.