| 摘要 |
PURPOSE:To obtain a filter with an excellent characteristic with less number of components by forming a resonance circuit by a lead of a lead capacitor and other inductor or a capacitor. CONSTITUTION:A channel signal from the 2nd mixer 19 is fed to an input terminal 40. A capacitor C1 and an inductor L1 act like the 1st stage resonance circuit. A capacitor C4 acts like a coupling capacitor and an inductor L2 and a capacitor C2 act like the 2nd stage resonance circuit. A lead capacitor is used as the capacitor C6, and the lead of the capacitor C6 and, e.g., the inductor L2 are arranged in the relation of electromagnetic induction coupling to form a characteristic being the addition of a new characteristic to the substantial band characteristic of the dual tuning circuit. That is, the lead of the lead capacitor C6 acts like the electromagnetic induction coupling with the next stage in common and the trap frequency is set.
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