Method of microwave measurement of dielectric permittivity in a small volume of high loss liquid

Abstract

We propose a new microwave method of dielectric permittivity measurement in a small volume (less than 5 × 10−2 cm3) of a high loss liquid sample. The method is based on the use of the hemispherical dielectric filled resonator, which contains a small hemispherical central cavity filled with the measured liquid. The characteristic equation for eigenfrequencies of electromagnetic oscillations in this resonator has been obtained and analysed. On this basis, the operating mode of oscillations and optimal sizes of the measuring cavity and resonator have been found. We discovered the effect of electromagnetic field extrusion of the small central cavity filled with the liquid at large values of the real and imaginary parts of the dielectric permittivity. The method has been implemented experimentally in the X band. The found theoretical effect of the field extrusion has been confirmed experimentally. The equation for the calculation of the complex dielectric permittivity of a liquid via the measured values of the resonator quality factor and resonant frequency has been found.