Coplanar Stripline Spurline Stub Resonators With Even-Mode Suppression for Bandpass and Bandstop Filters

Coplanar stripline (CPS) bandpass and bandstop filters may be built using spurline stub resonators. Previous papers have demonstrated these filters, but they had a parasitic resonance that may limit spurline resonators from being used in CPS. This letter explains the parasitic resonance and introduces an alternative circuit model of the stub and a method to suppress it.