2.5D Miniaturized Frequency Selective Rasorber with A Wide High-Transmission Passband

This letter presents a 2.5D frequency-selective rasorber(FSR) with a wide high-transmission(|S21|<1dB) passband and two absorption bands. The proposed FSR consists of a 2.5D lossy layer and a 2D lossless layer, between which is an air gap. At the top layer, a 2.5D convoluted resonator, which introduces large equivalent impedance to generate a wide high-transmission passband, is constructed in the center of lumped-resistor-loaded T-type metallic strips. A triple layer bandpass frequency-selective surface is adopted as the lossless layer. Procedures to develop an accurate equivalent circuit model (ECM), aiming at providing physical insights into the operating mechanism of the proposed 2.5D FSR, are discussed. The simulation results indicate that the proposed FSR has a 1dB transmission band from 7.81-11.78GHz with 40.53% relative bandwidth and 80% absorption bands covering 3.67-6.80GHz and 13.74-15.31GHz. A prototype of 2.5D FSR is fabricated and measured to validate the design.