A Broadband Tunable Absorber Based on a PIN diode-loaded frequency selective surface

In this paper, we design and fabricate a novel broadband tunable absorber based on a PIN diode-loaded frequency selective surface (FSS). The absorber is a four- layer structure, and from the top to the bottom are the active FSS (AFSS) layer, the dielectric substrate, the air layer and the metal ground. The AFSS layer is designed as a symmetrical strip with a PIN diode loaded in the middle, which have an adjustable resistance to obtain a tunable and broadband absorption capability. At the same time, a simple bias network is designed to supply an appropriate diode control voltage. The simulations show that the reflectivity can be adjusted below −10dB from 2.3 to 14.5 GHz and the rasorber achieved a broadband absorption. The measurement shows that the frequency range of the rasorber reflectivity less than −10dB is 2.35 to 13.44GHz by adjusting the voltage applied on the PIN diodes. The good agreement between simulations and measurements verifies our design. What's more, the absorber has an overall thickness of 7.524 mm, which is about only 0.059λ of the lowest working frequency and is superior to the conventional passive absorbers. In general, this broadband tunable absorber has great application value in wireless communication, antenna, stealth and radar detection, especially for C-band and X- band radar detection and stealth.