K. Wada et al., Characteristics of short-ended coplanar waveguide resonator with low spurious response and its application to a bandpass filter, IEICE TR EL, E82C(1), 1999, pp. 126-132
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.