Double Resonant Stub Bandstop Filter with Pseudo-Elliptic Response

Abstract: A simple wideband bandstop filter that yields equal ripples in both the pass and stop bands, is described. The filter comprises only of two resonant stubs and a connecting transmission line and has a transmission response almost identical to that of a third order elliptic function filter. The practical bandwidth is limited to 130-160%. Introduction: High rates of cutoff for wideband bandstop fitters are achieved if the filter prototype has a transfer function contributing transmission zeros at real frequencies away from the filter centre frequency, such as the elliptic function (Cauer) filters. The design procedures for transmission line filters employing elliptic function prototypes are widely described, and various forms of realizatio