Electronically tunable liquid crystal based Salisbury screen microwave absorber

In this paper we describe the design, manufacture and performance of an electrically thin (0.15 ¿) dynamically adaptive Salisbury screen absorber. The structure is backed by a high impedance surface which is constructed on a 250 ¿m thick liquid crystal substrate. The shift in the resonant frequency of the radar absorber is obtained by exploiting the voltage dependent anisotropic property of nematic state liquid crystals. Simulated results show that the reflection minimum is tunable over a 2.3% bandwidth and the reflectivity is below -10 dB in the frequency range 8.8-10.05 GHz (13%). Numerical predictions for normal incidence operation are shown to be in close agreement with experimental results when bias voltages are applied in the range 0 V to 20 V.