A Wideband Amplifying Frequency-Selective Rasorber Based on a 2.5-D Antenna-Circuit-Antenna Structure

This article proposes a 2.5-D wideband amplifying frequency-selective rasorber (AFSR). First, a 2.5-D antenna-circuit-antenna frequency-selective surface (FSS) based on the conventional 2-D surface-circuit-surface metasurface design was proposed, whi ch can reduce the design complexity of amplifying FSS (AFSS). To achieve a wideband passband, a patch antenna with a U-shaped slot serves as both a receiving and transmitting antenna. The power amplifier circuit is connected between the receiving and transmitting antennas to provide power amplification. The power amplifier circuit, transmitting antenna, and receiving antenna make up the AFSS. To achieve out-of-band absorption, a lossy layer, which is composed of metal wires with resistors and rectangular spiral resonators, is layered on top of AFSS. The equivalent circuits for the AFSS and AFSR have been derived. The lower absorption band ranges from 3.1 to 5.1 GHz, while the upper absorption band ranges from 7.3 to 9.6 GHz. The amplifying passband ranges from 5.2 to 7.2 GHz, with a maximum gain of 11.2 dB obtained through experimental results. The proposed AFSR can be used as the antenna’s radome to provide power amplification and RCS reduction, improve the detection distance and accuracy, and improve communication quality. The experimental and simulation results agree well. To the best of our knowledge, this is the first realization of an amplifying rasorber.