Title:
FILTER CIRCUIT
Document Type and Number:
WIPO Patent Application WO/2005/088832
Kind Code:
A1
Abstract:
A variable frequency filter in which a variation in cut-off characteristics is suppressed when the frequency is varied. The filter comprises two parallel resonance circuits, a coupling inductor coupling them, and a multipath circuit. The parallel resonance circuit comprises, connected in parallel, a resonance inductor and a series circuit of a variable capacitance element and a resonance capacitor. The multipath circuit comprises a coupling capacitor, and a variable capacitance element inserted between the coupling capacitor and each parallel resonance circuit. Since a variation in cut-off characteristics is reversed between the parallel resonance circuit and the multipath circuit when the frequency is varied, variations in cut-off characteristics are canceled when frequencies are varied simultaneously at the two and thereby variations in cut-off characteristics can be reduced when frequencies are varied.
Inventors:
FUJII MASAHIRO (JP)
Application Number:
PCT/JP2005/003616
Publication Date:
September 22, 2005
Filing Date:
March 03, 2005
Export Citation:
Assignee:
NEC CORP (JP)
FUJII MASAHIRO (JP)
FUJII MASAHIRO (JP)
International Classes:
H03H7/01; H03H7/09; H03H7/12; (IPC1-7): H03H7/12; H03H7/09
Foreign References:
| JPH10256809A | 1998-09-25 | |||
| JP2002009573A | 2002-01-11 | |||
| JP2001313580A | 2001-11-09 | |||
| JP2000165172A | 2000-06-16 | |||
| JP2001119257A | 2001-04-27 | |||
| JP2003045748A | 2003-02-14 | |||
| JPH08316767A | 1996-11-29 | |||
| JPS6418841U | 1989-01-30 |
Other References:
KAGEYAMA K. ET AL: "Tunable Active Filters Having Multhilayer Structure Using LTCC", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 49, no. 12, December 2001 (2001-12-01), pages 2421 - 2424, XP001067492
Attorney, Agent or Firm:
Miyazaki, Teruo (16th Kowa Bldg. 9-20, Akasaka 1-chome, Minato-k, Tokyo 52, JP)
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