A UWB Absorber Based on the TCA Concept in the UHF Band

A type of ultrawideband (UWB) absorber, comprising a tightly coupled array (TCA) in the UHF band, is proposed and designed in this communication. The absorber is based on the TCA concept and antenna reciprocity. Therefore, it inherits the UWB and ultrathin properties from TCAs. The proposed absorber consists of an air layer, a patterned indium-tin-oxide (ITO) film, and two layers of superstrate from an FR4 slab and a Teflon slab. The patterned ITO film is a resistive sheet to dissipate the received electromagnetic energy. The proposed absorber does not require the feed network, which is complicated for bipolarized and balanced TCA antennas. The fabricated absorber presents an absorption rate over 90% within a fractional absorption bandwidth of 135% from 0.23 to 1.183 GHz, and it has a thickness of $0.117\lambda $ at the lowest frequency. Moreover, the proposed absorber is polarization insensitive and angularly stable. The simulation and measurement results show that the TCA concept works well in design of ultrathin UWB absorbers.