Design of a Tunable Low-Frequency and Broadband Radar Absorber Based on Active Frequency Selective Surface

In this letter, we report on the design, fabrication, measurement, and analysis of a tunable low-frequency and broadband radar absorber applied in the frequency range of 1-12 GHz. Numerical simulations indicate that absorbers based on the resistor-loaded frequency selective surface (FSS) can be resistively tuned to give a broadband absorption of exceeding -10 dB between 1 and 12 GHz. Moreover, superior absorbing performance can be achieved by introducing capacitance paralleled with resistance. Measurement results show that the radar absorber, by way of configuration with active FSS (AFSS) controlled by p-i-n diodes, can be tuned to provide a continuously variable reflectivity level of less than -10 dB from 2 to 11.3 GHz with varied bias voltages. Furthermore, experimental results have good agreement with simulations.