Performance analysis of a tunable absorber based on active frequency selective surface

ZENG Xianliang, ZHANG Linxi, WAN Guobin*

School of Electronics and Information, Northwestern Polytechnical University, Xi'an 710072, China

Abstract: ［Objectives］A periodic absorber can absorb incident electromagnetic waves and effectively reduce the reflectivity of a target. To this end, a novel microwave absorber based on an active frequency selective surface (AFSS) is proposed in this paper. The absorption frequency bandwidth can be dynamically adjusted by adding one PIN diode to the unit cell.［Methods］First, the tunable reflection performance of the proposed absorber is studied by means of a full-wave electromagnetic simulator CST in order to investigate the reflectivity of the absorber diode as the equivalent resistance of the PIN diode changes with different forward current. The propagation and reflection properties of electromagnetic waves in a multi-layer structure is then analyzed using multi-reflection interference theory so as to quantitatively illustrate the magnitude and phase condition with regard to the near unity absorption. Finally, an experiment is conducted on a fabricated absorber to verify its effectiveness in an anechoic chamber.［Results］The results indicate that the reflectivity of the absorber can be effectively controlled within the range of 2.5–9.1 GHz after adding the PIN diode. ［Conclusions］The results of this paper have the potential to be applied in the electromagnetic stealth technology of weapons and equipment. Key words: stealth technology；active frequency selective surface (AFSS)；PIN diode；radar absorbing materials；reflectivity；interference theory