Electronically tunable UHF high-power filter

This report describes a research and development program that established the feasibility of a low-loss, high-power UHF resonator with electronic tuning means based on the 'L-Flauto' principle. This principle provides for changing the resonant frequency of a transmission-line cavity in discrete steps by using arrays of PIN diodes to short out inductances that are in series with the line. In an appropriate design, N switched inductances would provide 2N tuning channels selectable under binary-logic control. This kind of resonator has application to interference reduction in frequency-agile Air Force communication systems, where it would be used as a fast-tuning bandpass filter or as a tank circuit for a transmitter output stage.