Equivalent circuit for coaxial discontinuities filled with dielectric materials - Frequency extension of the Marcuvitz's circuit

An equivalent circuit for coaxial discontinuities is presented and discusse d. The cell used is a circular waveguide filled with a dielectric material measured in reflection/transmission. The circuit is obtained by using two w ell known methods: the Marcuvitz's circuit for a cell measured in reflectio n and an analytical resolution using the mode-matching method. The interest of the new circuit is that it has wider frequency and geometrical ranges t han the Marcuvitz's circuit and is much simpler than the mode-matching meth od. Using this circuit, complex permittivity can be calculated from measure ments of the S-parameters (S-11 and S-21). Experimental results are present ed up to 18 GHz. Frequency and geometrical ranges of validity are also disc ussed.