PSO-Assisted Design of a Dual-Polarized Broadband Switchable Rasorber/Absorber

This work presents a dual-polarized broadband switchable rasorber/absorber for applications requiring radar cross-section reduction. The rasorber/absorber is designed in a low-profile configuration using frequency selective surfaces (FSSs) on the both sides of two dielectric layers separated by an air gap. The top layer consists of a lossy square loop FSS loaded with lumped resistors and a bandpass FSS realized by four miniaturized slotted square patches inside the loop. The bottom layer has a square-slot-shaped lossless bandpass FSS. A partial set of initial geometry parameters is synthesized from the equivalent circuit model using particle swarm optimization to ensure rapid optimization of the geometry with good performance. Both the lossy and the lossless FSSs are loaded with p-i-n diodes to enable switching between rasorber and absorber modes. The design exhibits a lower absorption bandwidth from 4.2 to 7.2 GHz [fractional bandwidth (FBW) of 52.63%], an upper absorption bandwidth from 9.69 to 14.1 GHz (FBW of 37.07%), and a transmission band at 8.5 GHz with an insertion loss of 0.38 dB in the rasorber mode. In the absorber mode, the design exhibits a continuous absorption band from 4.6 to 11.1 GHz (FBW of 83%). The simulated results are validated through experimental measurements with good agreement.