Experimental determination of finline post discontinuity parameters: application to stopband and lowpass filters

The shunt reactance of a finline post discontinuity is shown to be of resonant type. By using an experimental transmission procedure, we have determined accurately the parameters R, L and C of its equivalent circuit. These parameters, in the first approximation, can be considered as frequency-independent. Thus the use of the equivalent circuit in CAD is very easy. Applications to stopband and lowpass filters are described.