| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a branching filter circuit, capable of obtaining an attenuation amount over a wide band and superior insertion loss characteristics for a pass band. <P>SOLUTION: The branching filter circuit is composed of a first filter connected between first and second ports P1, P2 and the pass frequency band of which is a first frequency band; and a second filter connected between first and third ports P1, P3 the pass frequency band of which is a second frequency band. The first filter is provided with a first inductive element L1 located between the P1 and P2; a first series resonance circuit of a second inductive element L2 and a first capacitive element C1 located between the P2 side of the element L1 and ground; and a parallel resonance circuit of a third inductive element L3 and a second capacitive element C2, located on the P2-side of the element L1. The first series resonance circuit has an attenuation pole in the second frequency band, the parallel resonance circuit has an attenuation pole within a frequency band exceeding twice the first frequency band and lower than thrice the first frequency band; and the resonance frequency of the first series resonance circuit is selected lower than the resonance frequency of the parallel resonance circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
