Microstrip patch with adaptive conductivity

We are investigating techniques that electrically change the conductivity of microstrip patch antennas. Altering the conductivity of certain areas of a patch antenna can be useful for controlling the weighting of elements in an array or for tuning the antenna to a desirable frequency. Materials that have adjustable conductivity include conductive electoactive polymers and silicon. Conductive electoactive polymers have a conductivity that is proportional to an applied electric potential. Polypyrroles and polyanilines are examples that exhibit changes in conductivity between 10"7 and 103 S/cm. Conducting polymeric materials have controllable conductivity at microwave frequencies. Applying a small dc potential across a poly(aniline)-silver-polymer electrolyte composite quickly changes its conductivity. These materials have been incorporated into a Salisbury screen to dynamically alter the radar cross section of large surfaces. In this paper, we report on modeling and experimental results aimed at creating a reconfigurable patch antenna partly made with high-purity silicon which has a conductivity that can be varied over a wide range using infrared illumination.