ANALYSIS OF DIFFERENT COAXIAL DISCONTINUITIES FOR MICROWAVE PERMITTIVITY MEASUREMENTS

In this paper, a comparative analysis of a coaxial line terminated by a circular waveguide filled with different types of dielectrics is use d for microwave permittivity measurements. The numerical results provi de a clear insight on the different methods of measurement, and on thi s basis the proper choice of the coaxial discontinuities can be made i ncluding the dimensions of the test sample to achieve wide bandwidth a nd enhancement of measurement accuracy at low frequencies. This paper also derives a new expression for calculating the permittivity of a sm all quantity of a material available only in limited quantities as is the case in certain biological materials (such as DNA).