| 摘要 |
PURPOSE:To attain the miniaturization of a branching filter itself and to reduce the cost by reduction in number of components by using a low-pass filter to apply branching operation thereby attenuating the spurious characteristic. CONSTITUTION:Low-pass filters 31, 41 having the same phase characteristic as that of a transmission line are connected between input terminals 1-1, 1-2 and band-pass filters 12, 22 in place of the line. The low-pass filters 31, 41 each consists of an inductance and a capacitance and acts like a branching filter circuit. In using, e.g., dielectric filters for the band-pass filters 12, 22, the spurious radiation produced from said filters is generated at three times or four times the center frequency f0 of the pass band normally, the spurious characteristic is suppressed by the low-pass filters 31, 41, which are miniaturized. Thus, the branching filter itself is miniaturized, number of components is reduced and low cost is attained.
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