Wide band automatic frequency control circuit

DETAILED DESCRIPTION An object of the present invention is to provide an enhanced automatic frequency control (AFC) circuit for a signal receiver.
Another object of the invention is to provide an AFC circuit having an improved "pull-in" range.
Still another object of the invention is to provide an AFC circuit utilizing potentials from sync pulse separation means to enhance the "pull-in" range of the system.
A further object of the invention is to utilize discriminator means and sync pulse separation means to improve the "pull-in" range of the system.
A further object of the invention is to utilize discriminator means and sync pulse separation means to improve the "pull-in" range of an AFC system.
These and other objects and advantages are achieved in one aspect of this invention by an automatic frequency control circuit for a television receiver having an intermediate frequency amplifier stage coupled to a tuner stage and by a detector stage to a video amplifier stage connected to a cathode ray tube.
The automatic frequency control circuit includes discriminator means coupled to the intermediate frequency amplifier stage, means coupled to the video amplifier stage for detecting sync pulses, and signal combining means.
The signal combining means is coupled to the discriminator means, the means for detecting sync pulses, and the tuner stage.
The signal combining means effects a given "pull-in" range of the tuner stage in response to error signals from the discriminator means and an increased "pull-in" range in response to a signal from the means for detecting sync pulses indicative of the absence of detected sync pulses.