Measurement of the Inner Dimensions of Microwave Cavity Resonators

Abstract

The accurate measurement of the internal dimensions of closed cavities with conducting walls without the access of measuring tools inside the cavities is relevant when measuring the parameters of radio materials and the dimensions of metal vessels with limited access to them, when clarifying the Boltzmann constant, and when conducting gas thermometry and other tasks. This article presents the results of measuring the internal dimensions of cavities, namely, microwave cavity resonators, by considering the range of their resonant frequencies. The differences between the eigenfrequency and resonant frequency in a resonator with perfectly conducting walls and those in a real resonator with impedance walls are clarified. The types of functions suitable for describing the resonant amplitude-frequency characteristics of real resonators are analyzed. This article also presents the results of measuring the inner diameter and length (height) of microwave resonators from the State Primary Standard for the units of complex dielectric permeability (GET 110-2012) with frequencies ranging from 1 to 178.4 GHz.