A Recording Microwave Refractometer

Abstract

An instrument designed to measure and record a small difference in frequency between two cavity resonators is described. A sweep frequency technique is used to generate the resonance responses of the cavities. These responses are sharpened and made to control the operating time of a trigger circuit, whose average output is metered. A sensitivity equal to 200 c.p.s. is obtained in the measurement of the frequency difference between two high Q cavities, whose resonance frequencies are equal to 9000 Mc. Applications of this instrument are discussed, especially those relating to measuring changes in dielectric constant. A simple extension of the present instrument is suggested for simultaneously recording changes in dielectric constant and loss.