Electronic Frequency Stabilization of Microwave Oscillators

TLDR

The authors describe two circuits that stabilize a microwave oscillator using an external high‑Q cavity and propose using these systems for high‑resolution microwave absorption spectroscopy. One circuit employs a microwave frequency discriminator with a d.c. amplifier, while the other generates an intermediate‑frequency signal from the cavity to measure the oscillator‑cavity frequency difference and drive an intermediate‑frequency amplifier.

Abstract

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.