Electronic Frequency Stabilization of Microwave Oscillators

Two circuits for use to control the frequency of a microwave oscillator by an external high Q cavity are described. One of the circuits uses a microwave equivalent of the frequency discriminator, in conjunction with a d.c. amplifier. The other uses the cavity in a special circuit that provides an intermediate-frequency signal that is a measure of the difference between the frequencies of the oscillator and cavity. This allows the use of an intermediate-frequency amplifier. The resulting stability of the oscillators is such that audible beat frequencies can be produced between two oscillators at 10,000 Mc/sec. The resultant signal can be frequency modulated at audiofrequencies, with stabilization acting throughout the modulation cycle. A technique by which the frequency-stabilization systems could be used to investigate, with high resolution, the structure of microwave absorption spectra is suggested.