Characteristics of Short-Ended Coplanar Waveguide Resonator with Low Spurious Response and Its Application to a Bandpass Filter

Kouji WADA

IEICE TRANSACTIONS on Electronics   Vol.E82-C    No.1    pp.126-132
Publication Date: 1999/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwave and Millimeter Wave Technology
coplanar waveguide,  short-ended resonator,  bandpass filter,  low spurious response,  

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Basic characteristics of a short-ended coplanar waveguide (CPW) resonator of good spurious suppression property is studied. The resonator is loaded with 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 frequency without degradation of unloaded Q(Q0). The origin and property of spurious response is thoroughly investigated to show the advantage and the limit of this configuration. The external Q(Qe) and fundamental resonant frequency 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 characteristics have been realized by the present filter in accordance with the expectation.