MICROWAVE INTERFEROMETER

Abstract

The design and operation of a two-beam microwave interferometer (A =-- 3.2 cm.) using two horns connected to the microwave source by a waveguide is discussed.In order to assess the usefulness of the inter-ferometer, the dielectric constants of some solid insulating materials have been measured. Results obtained using ordinary commercial sheets of materials agree within a few percent. with values obtained by other methods.The effect of diffraction on phase shift and hence dielectric con-stant has been investigated. The minimum size of a sample necessary for minimising the effect of diffraction has been determined. The sizes of the sample required for various angles of incidence compared to that at normal incidence have been determined and the results are in agreement with the values obtained theoretically.The probable error in the measurement of shift for different materials lies between ± 0-008 to ± 0.024 cm. The value of the dielectric con- stant measured at normal incidence agrees within 1.5% with the value obtained at Brewster's angle after necessary correction.