Varactor -based technologies for the tuning and control of microwave circuits and antennas

A monolithic optically variable capacitor (OVC) technology has been developed for the bias free optical control of microwave circuits and antennas. The components of the monolithic OVC, which include a Schottky varactor diode, 10-cell photovoltaic array and passive microwave structures, have been simultaneously fabricated and integrated on the same wafer. The monolithic OVC has been incorporated as the tuning/control element in band-reject filters, X-band analog phase shifters and folded slot antennas. Bias free control of these circuits/antennas has been demonstrated at microwave frequencies using less than 500 muW of optical power. This is the lowest reported optical power requirement for the bias free control of microwave circuits/antennas.;Encouraged by the performance of the optically controlled phase shifters, which utilized the varactor loaded transmission line topology, it was decided to use varactor loaded transmission lines to implement electronically controlled analog phase shifters. An optimum design for analog phase shifters with the lowest possible insertion loss for a given varactor and transmission line technology was developed. As a result of these efforts, an electronically controlled 0--360° phase shifter with only 4.2 dB of loss at 20 GHz was demonstrated. This is best reported performance for electronically controlled analog phase shifters operating in the K-band.