| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that, when the number of filter stages is reduced, in a conventional filter circuit, a loss can be reduced in a desired band but smoothness of the loss within the band and a great out-of-band attenuation characteristic can not be obtained and that, when the number of stages is increased oppositely, flat loss characteristics within the band and a great out-of-band attenuation amount can be obtained but the loss is increased within the band. SOLUTION: In a filter circuit, a T-type circuit 5 and aπ-type circuit 8 constituted of inductors and capacitors are connected in parallel in such a way that, input impedances of these T-type circuit andπ-type circuit become a double of power supply impedance, respectively, and cut-off frequencies of the T-type circuit and theπ-type circuit become approximately equal. COPYRIGHT: (C)2009,JPO&INPIT
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