An X-band meta-structure absorber based on gelated deep eutectic solvent

Abstract

Herein, a meta-structure absorber (MSA) with gelated deep eutectic solvent (DES) is proposed and investigated at X-band (8.2–12.4 GHz). The ionic property of DES gel assists in enhancing absorption. The unit cell of the MSA is designed using a dumbbell-shaped resonating structure of gelated DES enclosed in a flexible silicone rubber substrate. The embedded dumbbell structure makes the MSA robust by promoting fast recovery after bending. The developed absorber is optimized for wideband absorption. The total thickness of the MSA is <3 mm. The measured results showed −40.02 dB reflection loss at 10.55 GHz with a −10 dB bandwidth of 3.34 GHz (9.06–12.4 GHz). Additionally, the proposed absorber shows polarization and incident angle insensitivity up to an angle of ±50° in both transverse electric and transverse magnetic modes. The mechanism involved in absorption is investigated through field analysis at resonating frequency. Possible application of the designed absorber in antenna isolation is studied for co-sited broadband horn antennas operating at the X-band.

RCS reduction using embedded meta-structure absorber in X-band

“…Ethaline is a DES prepared by mixing choline chloride and ethylene glycol in 1 : 2 molar ratio. In the earlier work done by the authors [22], 22 wt.% of gelatin in DES produces a highly viscous gel with good shape retention and elasticity. The gelated DES has a high dielectric loss tangent with values ranging between 0.65 and 1.05 throughout the X-band.…”

“…The permittivity of the gel is 16.39 − j15.044 while that of silicone rubber is 3.16 − j0.12 at the mid-frequency of the Xband. The values are retrieved from the previous work conducted by the authors in [22]. Silicone rubber is found to have a higher tensile strength of ∼ 1.6 MPa and elongation at break of 600% than other metastructure absorber substrates, such as FR4 (tensile strength of ∼ 282 MPa and elongation at break of 1.95% [33]) and acrylonitrile butadiene styrene (tensile strength of ∼ 43.8 MPa and elongation at break of 7.2% [34,35]).…”

“…Conducting ionic gels are found to have high dielectric loss in the microwave range [20][21][22]. An MSA is proposed with deep eutectic solvent-based gel (DES gel) resonating structures embedded and distributed periodically in a silicone rubber matrix.…”

“…DES gels are a neoteric subclass of room-temperature polymerized liquids [20,[23][24][25][26][27][28][29]. Silicone rubber as a substrate has good tensile strength, hydrophobicity and high temperature resistance [22]. Simulation and optimization of the MSA design are done prior to fabrication.…”