Patent ID: 8115574

Claim:
A microwave filter, comprising: a stepped impedance frequency filter section, having a plurality of resonator sections, arranged in a succession, each resonator section coupled to at least one other resonator section, an inner conductor coupled to at least one of the resonator sections and having a distal end, wherein the plurality of resonator sections are structured to provide a given pass band having a given sharpness of a given transition band, and a notch resonator coupled to the distal end of the inner conductor, said notch resonator comprising a first transmission line having a bore, a dielectric spacer arranged in the bore, the dielectric spacer having a second bore, a projection arranged to have a length LN within the second bore and to space the projection a gap GP from the bore, the projection connecting to a second transmission line, wherein the projection extending the length LN in the bore and the gap GP form an impedance equivalent to a coupling capacitance CC coupling to a resonant circuit comprising a parallel inductance LR and capacitance CR to a ground, and wherein the notch resonator has a notch frequency proximal to said pass band to provide the microwave filter with a transition band sharper than said given sharpness.