| 摘要 |
PURPOSE:To achieve excellent broadcast reception by applying the output of a signal holding circuit to a high-cut control circuit and by increasing high-frequency attenuation according a rise in signal level. CONSTITUTION:In an area where multipath reflection is occurring, an AM component mixes as echo distortion in a demodulated signal front end 2 owing to the time lag between the direct wave and reflected wave of the same broadcast radio wave. This distortion is detected through the AM detection of echo distortion detecting circuit 8 to output a distortion detection signal. The rising part of the distortion detection signal is outputted as it is and the rising part is converted into a waveform which falls slowly with a large time constant; and the output of signal holding circuit 9 is applied to high-cut control circuit 10. Then, the high-frequency attenuation of high-cut filter 11 increases as the signal level rises and when the distrotion reaches its maximum, the high-frequency attenuation of high-cut filer 11 is maximized. Consequently, a noise due to the echo distortion is eliminated to achieve excellent broadcast reception. |
