Broadband Polarization-Insensitive Tunable Absorber Using Active Frequency Selective Surface

In this letter, a broadband polarization-independent tunable absorber is proposed based on active frequency selective surface (AFSS). The AFSS consists of periodic patterns of four-patch array with four p-i-n diodes loaded among them, and a simple bias network is designed behind the ground plane through metalized via holes, which can effectively reduce the influence on the absorbing performance. By changing the bias voltage applied on the p-i-n diodes, the reflectivity of our absorber can be dynamically adjusted from near-unity reflection to less than −10 dB absorptivity under normal incidence over a wide frequency band ranging from 8.5 to 18.2 GHz. Due to the symmetrical structure of the AFSS, our absorber still has polarization insensitivity. We fabricated this AFSS absorber sample, and its measured results agree well with the simulated ones.