Characteristics of short-ended coplanar waveguide resonator with low spurious response and its application to a bandpass filter

Basic characteristics of a short-ended coplanar waveguide (CPW) resonator o f good spurious suppression property is studied. The resonator is loaded wi th open tubs at its middle position and makes a fully planar structure. The length of the resonator is shortened almost by half and the first spurious resonance goes up to more than 3 times of the fundamental resonant frequen cy without degradation of unloaded Q(Q(0)) The origin and property of spuri ous response is thoroughly investigated to show the advantage and the limit of this configuration. The external Q(Q(e)) and fundamental resonant frequ ency of the resonator are also clarified theoretically and experimentally. Using those result, a bandpass filter (BPF) is designed on the basis of the narrow band approximation is realized and its transmission characteristics are examined theoretically and experimentally. The spurious suppression ch aracteristics have been realized by the present filter in accordance with t he expectation.