| 摘要 |
PURPOSE:To obtain a band-pass filter which is compact and improves a filter characteristic better by capacitorcoupling plural resonators and connecting one place between the resonators with the serial circuit of a coil and a capacitor. CONSTITUTION:Resonators Q1 and Q2 are capacity-coupled by a capacitor Cs. The resonators Q1 and Q2 are connected by a serial circuit composed of a coil L7 and a capacitor C6. The resonators Q1 and Q2 have an equivalent circuit to connect second capacitors C2(C4) in parallel to an LC serial circuit in which coils L1, L2(L3, L4) are serially connected to both sides of capacitors C1(C3). Then, at both sides of a central frequency and close to the central frequency, a pole is formed and a sharp filter characteristic is obtained. Thus, the band-pass filter, which is compact and improves a filter characteristic better, is obtained.
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