| 摘要 |
PURPOSE:To improve the selectivity of up-and-down tuning frequencies, by capacitive coupling between the primary side of dual tuning circuit and the input side of mixing circuit, and by inductive coupling between the seondary side of dual turning circuit and the input side of mixing circuit. CONSTITUTION:A trap frequency omega1 is set and the selectivity to higher frequency can be improved, by using the inductive coupling between the resonance line L2 and the coupling loop L3 as the coupling circuit to a mixing circuit 4. On the other hand, the trap frequency omega2 is formed at the lower side than the tuning frequency to improve the selectivity of lower frequency, by capacitive coupling between the hot point side of the resonance line L1 and the input side of the mixing circuit 4 with a capacitor CX. |
