Switchable Broadband Dual-Polarized Frequency-Selective Rasorber/Absorber

This letter presents a switchable dual-polarized frequency-selective rasorber/absorber at low microwave frequency based on double-layered metallic resonant structure array loaded with lumped elements. It consists of an absorbing layer and a bandpass frequency-selective surface layer loaded with PIN diodes, sandwiched with an air-spacer between them. The operating principle is analyzed with the help of an equivalent circuit model. By biasing the PIN diodes on or off, it can be easily switched between the rasorber and absorber modes. When in the rasorber mode, it exhibits a passband at 1.6 GHz with 1.7 dB insertion loss between two neighboring absorption bands. While switched to the absorber mode, it achieves more than 80% absorptivity ranging from 0.8 to 3.4 GHz, corresponding to a fractional bandwidth of 124%. The total thickness is less than 8% of the free-space wavelength at the lowest operating frequency. A prototype of the proposed structure is fabricated and measured, where reasonable agreements between simulations and measurements are observed.