Frequency synthesizer tuning system with manual fine tuning control

A frequency synthesizer tuning system for a tuner of a television receiver capable of receiving a composite television signal and including automatic fine tuning (AFT) circuit means producing an AFT signal, said system including in combination:

• reference oscillator means providing a reference signal at a predetermined frequency;
• local oscillator means in the tuner providing a variable output frequency in response to the application of a control signal thereto;
• a programmable frequency divider having an input coupled to the output of said reference oscillator means for producing an output signal having a frequency which is a programmable fraction of the frequency of the signal applied to the input thereto from said reference oscillator means;
• means coupled to the output of said programmable frequency divider and said local oscillator means for developing a control signal and applying such control signal to said local oscillator means for controlling the frequency of operation thereof;
• first control means coupled to the output of the AFT circuit means and further coupled to said programmable frequency divider for controlling said frequency divider to change said programmable fraction in response to predetermined signal conditions of the AFT signal;
• and
• manual fine tuning control means coupled to said first control means and to said programmable frequency divider for disabling said first control means and for controlling said frequency divider to change said programmable fraction in response to operation thereof.

A frequency synthesizer tuning system for a tuner of a television receiver capable of receiving a composite television signal having at least carrier signal components and synchronizing signal components, said system including in combination:

• reference oscillator means providing a reference signal at a predetermined frequency;
• local oscillator means in a tuner providing a variable output frequency in response to the application of a control signal thereto;
• programmable frequency divider means having an input coupled to the output of said reference oscillator means for producing an output signal having a frequency which is a programmable fraction of the frequency of the signal applied to the input thereto from such reference oscillator means;
• means coupled to the output of said programmable frequency divider means and said local oscillator means for developing a control signal and applying such control signal to said local oscillator means for controlling the frequency of operation thereof;
• carrier sensing means coupled to receive at least the carrier signal components of the composite signal and providing an output voltage indicative of the tuning of said receiver to a carrier component of said composite signal;
• synchronizing signal components sensing means coupled to receive at least said synchronizing signal components of the composite signal for providing a first predetermined output with synchronizing signal components sensed thereby;
• first control means coupled to the outputs of said carrier sensing means and said synchronizing signal components sensing means and further coupled to said programmable frequency divider means for changing said programmable fraction in response to predetermined signals at the outputs of said carrier sensing means and said synchronizing signal components sensing means;
• and
• manual fine tuning control means coupled to said first control means and to said programmable frequency divider and operable to disable said first control means and to change said programmable fraction of said programmable frequency divider to a predetermined manner.

A frequency synthesizer tuning system for a tuner of a television receiver capable of receiving a composite television signal, said system including in combination:

• reference oscillator means providing a reference signal at a predetermined frequency;
• local oscillator means in the tuner providing a variable output frequency in response to the application of a control signal thereto;
• a programmable frequency divider having an input coupled to said reference oscillator means for producing an output signal having a frequency which is a programmable fraction of the frequency of the signal applied to the input thereto from said reference oscillator means;
• means coupled to the output of said programmable frequency divider and the output of said local oscillator means for developing a control signal and applying such control signal to said local oscillator means for controlling the frequency of operation thereof;
• channel selection means coupled to said programmable frequency divider for establishing a predetermined initial programmable fraction therein each time a new channel is selected by said channel selection means;
• and
• manual fine tuning control means coupled to said programmable frequency divider for controlling said frequency divider to change said programmable fraction thereof according to the operation of said manual fine tuning control means.