A Frequency Stabilization System for Microwave Gas Dielectric Measurements

A system is described for measunng the dielectric constant of a gas at uhf by observing the shift in resonant frequency of a cavity when filled with the gas to be measured. To do this, a klystron oscillator is stabilized with great precision on the cavity resonant frequency by means of a double-loop servo system. One loop is of the Pound type, which is effective against almost all frequency fluctuations. The other is a motor-type control which further reduces any small, steady, frequency error left by the electronic Pound loop. The two combine to give control that is better than one part in 108, and this is sufficient to obtain values of (no-1), where no is the index of refraction, accurate to three places.