Ultrawide Bandwidth Electromagnetic Wave Absorbers Using a High-capacitive Folded Spiral Frequency Selective Surface in a Multilayer Structure

Tian Liu,Sung-Soo Kim

doi:10.1038/s41598-019-52967-z

Abstract

A high-capacitive frequency selective surface (FSS) with a new structure of folded spiral conductors is proposed as the small-array periodicity and low-frequency resonance FSS for ultra-wide bandwidth absorbers in a multilayer structure. Due to the folded structure with long effective segments and a small gap, a large value of capacitance for the lowest resonating frequency is obtained. Through a combination of the high-capacitive spiral FSS with other conventional FSSs (square loop, square patch) with a medium- and high-frequency resonance, an ultra-wide absorption bandwidth (4.7–50.0 GHz for −10 dB reflection loss) is designed with a small total thickness of 7.0 mm, which is close to the theoretical limit (6.7 mm). Admittance analysis is conducted for better insight into the optimization procedure. The free space measurement with a test sample prepared by the screen printing method also demonstrates a wide-bandwidth absorption result (5.2–44.0 GHz for −10 dB reflection loss, total thickness = 6.5 mm), which is in good agreement with the simulation result. In addition, the angular stability of the proposed wide-bandwidth absorber is discussed for both TE and TM polarizations in association with unit cell periodicity and grating lobes.

Highlights

Rozanov[2] demonstrated a physical bound on the lowest achievable frequency of an absorber, which is given by fL = cΓ0/172d for a multilayered non-magnetic absorber, where c is the velocity of light, Γ0 is the reflection coefficient in dB, and d is the total thickness of the absorber
The minimum possible periodicity with a low resonating frequency as well should be required for the design of ultra-wide bandwidth absorbers, which can be accomplished by using an frequency selective surface (FSS) with large circuit parameters
Through a combination of the high-capacitive spiral FSS with other conventional FSSs with a medium- and high-frequency resonance, we designed an ultra-wide absorption bandwidth (4.7–50.0 GHz for −10 dB reflection loss) with a small total thickness of 7.0 mm, which is close to the theoretical limit

Summary

Introduction

In our previous study[30], through a layer combination of two FSS patterns with different resonating frequencies, an ultra-wide absorption bandwidth (6.3–40.0 GHz (FBW = 145%) for −10 dB reflection loss) was designed with a small total thickness of 5.5 mm (0.11λL).

Results

Conclusion