Progress in smart microwave materials and structures

Abstract

Smart windows that regulate the transmission of visible light are well known, but with the continuing interest in modifying the radar signature of military hardware, there is a need also for smart microwave windows and surfaces. The paper reviews progress on the fabrication and characterization of poly(aniline)-silver-polymer electrolyte composite materials. Discs and films of this material have been characterized over the frequency range 0.5-18 GHz. The materials demonstrate a rapid and reversible change in their microwave reflectivity when a small dc potential is applied across them. The best samples have exhibited a reflectivity change in excess of 20 dB in a coaxial line test set. Cyclic voltammetry studies of these composite materials are discussed in the light of a poly(aniline)|polymer electrolyte|silver single-cell model. The effect of the poly(aniline) counter ion, the polymer electrolyte and the application of a bias potential on the dc and microwave results is discussed. Geometries of smart surfaces that might utilize these materials are then proposed and their characteristics are evaluated.