| 摘要 |
PURPOSE:To reduce the buzz interference by adopting the frequency characteristics at the input state of the intercarrier detection circuit as those not causing phase modulation, in the TV receiver of intercarrier system which can receive audio multiplex broadcast. CONSTITUTION:The intermediate frequency output via the tuner 1, input filter 2 and video intermediate frequency amplifying circuit 3 is fed to the audio trap circuit 4 and the correction filter 8. The frequency characteristics B of the filter 8 is selected higher than the video intermediate frequency fp at the resonance frequency fo, and the slope is selected as opposite slope alpha than the slope -alpha which is the normal Nyquist strobe given to the IF characteristics of the input filter 2 at the specified band DELTAf taking the frequency fp. When DELTAf is taken double or more the horizontal synchronizing signal frequency fH, and when the output signal of the correction filter 8 is made for intercarrier detection via the tuning circuit 9 to the audio carrier, the phase shift of the video carrier is cancelled and phase modulation component is avoided, the equivalent FM component is zeroed to avoid the production of buzz, thereby remarkably improving the buzz interference to the sub-channel. |
