Monolithic optically variable capacitors for tunable microwave antennas

Optical fiber links are low loss, light weight, compact, immune against EMI and do not interfere with the radiation patterns of antennas. This makes them attractive for the control of microwave circuits and antenna arrays. In this paper we report a monolithic implementation of an Optically Variable Capacitor. This consists of a photovoltaic array that generates a light dependent reverse bias voltage across a varactor diode. The fabrication of miniature photovoltaic arrays poses some interesting challenges which are addressed in this paper. The DC characteristics of the photovoltaic arrays and RF measurements on the entire Optically Variable Capacitor are presented.