Wide-angle, dual-polarized frequency selective rasorber based on the electric field coupled resonator using characteristic mode analysis

A wide-angle, dual-polarized frequency selective rasorber (FSR) with two absorption bands located at both sides of a passband is proposed. The structure comprises a lossy frequency selective surface (FSS), a bandpass FSS, and an air spacer located in between. A modified electric field coupled (ELC) resonator is used as a parallel resonance at the lossy layer to achieve a passband within the absorption band. The characteristic mode theory is utilized to investigate the absorption behavior of the lossy layer. Extensive simulations were carried out to assess the performance of the presented structure. Under the normal incidence, the proposed structure provides an operating bandwidth (|S-11| < -10 dB) from 1.94 to 7.16 GHz, corresponding to a fractional bandwidth (FBW) of 114.7%. The achieved passband is around 4.3 GHz with a minimum insertion loss of 0.81 dB. The absorption bands with an absorption rate higher than 80% are 1.81-3.69 GHz (FBW of 68.4%) in the lower band and 4.95-7.43 GHz (FBW of 40%) in the upper band, respectively. It exhibits quite stable characteristics up to 50 degrees angle of incidence. Furthermore, a prototype was fabricated and measured, which confirms that a good agreement exists between the experimental and simulation results. The proposed FSR is a suitable candidate for lowering the radar cross section (RCS) of the communication equipment or making them stealthy.