Investigation of finiine strip discontinuities and its application to millimeter wave filters

Up to now the finlines proposed by Meier as MMW transmission line for fMW integrated circuits have been used by components designers with growing interest and importance. There has been an increasing activity concerning the theoretical foundations of the discontinuities of finlines in order to lead eventually to a more sophisticated CAD program of printed E-plane circuits. But only few research has been carried out for the general case when the fin slot is less than the height of housing.[1,2] The results are emperical or approximate. No rigorous results are available. In this paper the general case of finline strip discontinuities is first investigated rigorously by resonance method and variational technique and a set of design charts are evaluated. Using these results Ka-band band pass filters with unilateral and bilateral finline strips have been realised demonstrating the feasibility of the employed equivalent circuit approach. The measured results agree well with the theoretical predictions. The measured minimum insertion losses at pass band are 0.64 dB and 0. 52 dB respectively.