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Thesis (M.S.)—University of Nebraska—Lincoln, 1968. Department of Electrical Engineering.


Copyright 1968, the author. Used by permission.


The purpose of this thesis is to describe the design of electronic circuitry for accurately locking the average frequency of a klystron tube to the resonant frequency of a high-Q microwave cavity which contains air and an unknown amount of water vapor.The reflex klystron is frequency modulated with a 10 KHz sine wave which sweeps the klystron frequency over a narrow range in the vicinity of the cavity resonant frequency.Modulating signal and crystal detector signal are compared in a switching detector circuit which accumulates an error signal.Feedback transmission of the error signal to the repeller electrode of the klystron is accomplished by a phototransistor optical coupling.Integrated circuits are used for signal and error amplification.The results show that sensitivity of the control circuit is approximately 1.11 MHz per dc volt of error signal.Frequency bandwidth in which the serve-loop circuit will lock onto the resonant frequency of the cavity is approximately 5 MHz at a center frequency of 11 GHz.The system described requires less equipment and complex circuitry than other methods presently in use.

Advisor:Allen R. Edison