Microstrip bandpass filters with attenuation poles due to dual-mode behaviour

This paper proposes microstrip bandpass filters consisting of a half-wavelength resonator and quarter-wavelength stubs set at the center of the resonator. The proposed filter easily and compactly produces the bandpass characteristic due to the dual-mode operation and also bandstop one having attenuation poles in both outside regions of the passband. The usefulness of the present filters are also verified from measuring transmission characteristics of the fabricated filters.