ON THE NARROW-BAND MICROWAVE FILTER DESIGN USING A DIELECTRIC ROD

A numerical method is presented for designing bandpass or bandstop filters in the microwave region. The procedure is based on an analysis of the discontinuity problem of a circular cylindrical dielectric rod centered in a rectangular waveguide. The authors first determine the zeros of the reflection and the transmission coefficients for a dielectric post with various permittivities and various radii. After a numerical procedure, they use some easy-to-use curves where the resonant frequency of the filter, the dielectric constant, and the radius of the post are related. Experimental results for filter design with the help of plastic and porcelain rods are given.