Automatic tuning unit

Abstract

Abstract PURPOSE:To increase the channel selection speed in digital channel selector, by providing the means to pick up the horizontal synchronizing signal or its vicinity for the signal obtained through frequency discrimination. CONSTITUTION:The output of the frequency discrimination circuit 8 is rejected for the video carrier, and the video component in amplitude modulation is fed to the gate circuit 13 via the smoothing circuit 12 having small time constant not filtered. Since this gate circuit 13 takes the horizontal deflection pulse or the synchronizing signal in amplitude separation as the gate signal S, this output is almost a constant amplitude pulse train signal not effected with the degree of modulation of the video signal. Accordingly, the S-shaped voltage waveform not depending on the degree of modulation of the video signal is obtained by passing through this output to the smoothing circuit 14. Further, the time constant of the smoothing circuit 14 can also be set smaller, the lowering in the channel selection speed by the time constant can be avoided and the speed can be increased.

Inventors

• 👤 Takeshi Arai

Bibliographic Details