Tunable Frequency Selective Surfaces Characterisation

In this paper a new means for accurate characterisation of active varactor loaded frequency selective surfaces (FSS) is demonstrated. The varactor loaded active doubly periodic wire FSS acts as a variable impedance surface, in which its surface reflectivity and transmitivity can be modified by adjusting by d.c. bias voltage control. The properties of the active FSS are characterised using a specially designed parallel plate waveguide (PPW) simulator. This permits normal incidence excitation of the FSS under test over the frequency range of 2.6 GHz to 3.95 GHz. In addition we present a novel hybrid de-embedding technique to remove the influence the PPW simulator and reveal the true property of active FSS. Typical results are presented and validated against a new 3D EM modelling led de-embedding method for the composite FSS and PPW structure.