Patent ID: 7911294
Filing Date: 2011-03-22
Classification: H03H

Abstract:
1. A variable-frequency band-elimination filter comprising: a plurality of series resonance circuits each of which includes an inductor and a capacitor connected in series to each other and a first end as a grounding end; a matching circuit connected between second ends of two of the plurality of series resonance circuits which are adjacent to each other; a switching element disposed between each of the grounding ends of the plurality of series resonance circuits and the ground so that the switching element is directly connected to the ground; a frequency shifting inductor via which a connection point between each of the grounding ends of the plurality of series resonance circuits and the switching element is connected to the ground in a conductive state at high frequency; and an input/output terminal connected to each of the second ends of two end series resonance circuits of the plurality of series resonance circuits which are at both ends of the plurality of series resonance circuits; wherein resonance frequencies of the plurality of series resonance circuits are similar to, but not the same as, one another; and the matching circuit is arranged to perform matching between the two of the plurality of series resonance circuits in a range including the resonance frequencies of the two of the plurality of series resonance circuits.