When Liquid Meets Frequency-Selective Rasorber: Wideband and Switchable 3-D Frequency-Selective Rasorber

TL;DR

This paper introduces a switchable 3-D frequency selective rasorber that uses a liquid microwave absorber within a waveguide to achieve wideband absorption and switchable band-notched functionality, demonstrated through design, fabrication, and measurements.

Contribution

It presents a novel liquid-based switchable FSR with wide absorption bands and reconfigurable functionality without lumped components or magnetic absorbers.

Findings

Achieved a passband at 5.10 GHz with 18.5% bandwidth and less than 3 dB insertion loss.

Demonstrated a broad absorption band from 2.5 to 4.6 GHz and 5.7 to 16.5 GHz.

Validated good agreement between analysis, simulation, and measurements.

Abstract

In this paper, a switchable 3-D frequency selective rasorber (FSR) with wide absorption bands without lumped components or commercial magnetic absorbers is presented and investigated. The absorption path is constructed by embedding a hybrid liquid microwave absorber (MA) inside a parallel plate waveguide (PPW) to create an extra-wide absorption band. A reflection layer based on water is placed behind the FSR to realize the reconstruction from FSR to a band-notched absorber (BNA) by controlling the presence or absence of water. The liquid-based absorber is firstly analyzed by a multimode dielectric resonant circuit and the fundamental operating principle of the FSR is demonstrated with the help of an equivalent circuit model (ECM). A design example is provided, fabricated, and measured and it exhibits a passband at 5.10 GHz with a transmission bandwidth of 18.5% for less than 3 dB insertion loss and fractional bandwidth of 146.8% with reflectivity less than -10 dB in FSR mode. In BNA mode, it has a minimum return loss of 0.72 dB and a good absorption band from 2.5 to 4.6 GHz and 5.7 to 16.5 GHz. Good agreements among circuit analysis, simulation results, and measurement results are finally obtained. The switchable rasorber can be applied in a shared-aperture antennas system to convert a broadband stealth radome into a BNA.