| US 7,573,356 B2 | ||
| Tunable filter | ||
| Kunihiro Kawai, Yokohama (Japan); Hiroshi Okazaki, Yokosuka (Japan); and Shoichi Narahashi, Yokohama (Japan) | ||
| Assigned to NTT DoCoMo, Inc., Tokyo (Japan) | ||
| Filed on Feb. 22, 2007, as Appl. No. 11/677,878. | ||
| Claims priority of application No. 2006-053853 (JP), filed on Feb. 28, 2006. | ||
| Prior Publication US 2007/0200651 A1, Aug. 30, 2007 | ||
| Int. Cl. H01P 3/08 (2006.01) | ||
| U.S. Cl. 333—205 [333/225; 333/235] | 20 Claims |
| 1. A tunable filter, comprising:
an input/output line formed on a dielectric substrate;
at least two coupling sections inserted in series in the input/output line at a distance from each other in the longitudinal
direction of the input/output line, each of the coupling sections including a gap dividing the input/output line in a width
direction thereof, and one or more coupling electrodes arranged in the gap in the longitudinal direction of the input/output
line;
a resonator connected to the input/output line between every adjacent two of said coupling sections and configured to vary
a resonance frequency thereof;
switch means for performing at least one of selective grounding of the coupling electrodes of the coupling sections and selective
short-circuiting among the coupling electrodes or between the coupling electrodes and the input/output line to vary a frequency
bandwidth of each coupling section; and
resonance frequency varying means for varying the resonance frequency of the resonator in association with the switch means.
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