| 摘要 |
PURPOSE:To prevent the degradation of a sound quality through the operation of noise elimination regardless of no multipath reception, by avoiding high-frequency attenuation until the AM detection value of an FM intermediate frequency signal exceeds a prescribed value. CONSTITUTION:In a multipath detection circuit 8, a diode D3 is connected between a capacitor C4 and a resistor R3. If an IF output signal ei has an amplitude change due to the change in the rate of change of FM modulation factor, the AM detection is made by diodes D1 and D2, a voltage charged in the capacitor C4 is at a forward voltage VD or below of te diode D3, then the diode D3 is turned off, no charging voltage of the capacitor C4 is applied between resistors R3 and R4, a control signal e0 is zero volt, and a high cut-off circuit 5 does not attenuate high frequencies of the detected signal and an audio output is made from a speaker 7 as it is. |
