Absorptive Frequency-Selective Reflector With Switchable Reflection Band and Its Application in RCS Reduction of Antennas

An absorptive frequency-selective reflector (AFSR) with a switchable reflection band is proposed to achieve a switch between absorption-reflection-absorption (A-R-A) mode and wideband absorption (WA) mode. The AFSR is composed of triangular hybrid resonators loaded with lumped resistors at the top layer, hexagonal patches loaded with PIN diodes at the bottom layer and a backed metal layer. The AFSR can be readily deployed as an antennas' ground plane or reflector for RCS reduction, which is verified by a bow-tie antenna. Simulation and measured results show that the AFSR increases the antenna gain by 1.43 dB at 6 GHz compared to a perfect electric conductor ground. Besides, the AFSR significantly reduces the out-of-band RCS in two absorption bands when it operates at A-R-A mode. Both in-band and out-of-band RCS are reduced if it works at WA mode as the reflection band is switched off.