Differential waveguide cuvette for complex permittivity measurement of high loss liquids at microwaves

A differential microwave waveguide cuvette for complex permittivity of high loss liquids measurement with high accuracy has been designed and studied. This cuvette is the main part of a waveguide-differential dielectrometer. The cuvette consists of two circular waveguide cells with central low loss dielectric rod surrounded by high loss liquid under test. These two cells have different lengths to eliminate complex propagation coefficient measurement errors due to diffraction effect on the ends of the layered waveguide cells at the junctions to the waveguide channel. The experimental dependences of the complex wave propagation constant on the operating frequency and on the water-alcohol solution concentration were obtained. The proposed structure can be applied as a measuring cuvette for the determination of the complex permittivity of various high loss liquids in small volume.