Television tuning apparatus
AssigneeThomson Consumer Electronics, Inc.
InventorDavid Mark Badger
Life of this patent
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Abstract
The invention concerns an arrangement including a microprocessor controller, PROM memory, and a digital to analog converter (DAC) arrangement for generating a plurality of control voltages for trimming respective ones of a plurality of varactor controlled tunable filters. The controller couples digital control signals to the respective DACs which generate respective analog control voltages which are applied to the respective tunable filters. A tuning voltage generated by a closed control loop, such as phased locked loop also under the control of the controller, is combined with the output control voltages generated by the respective DAC's in a resistance divider arrangement.
Claims5
In a tuning system including input means for receiving a plurality of RF signals corresponding to respective channels and frequency selection means for selecting one of said plurality of RF signals corresponding to a respective selected channel, apparatus comprising:
- a tunable circuit coupled between said input means and an output and cooperating to control frequency characteristics of apparatus coupled between said input means and said output, said tunable circuit including a reactive element having a reactive value determined by a magnitude of an analog control signal;
- means for selecting a channel;
- means for providing a digital control signal in response to the frequency of said selected channel;
- means for converting said digital control signal to a corresponding pulse control signal;
- means for generating an analog tuning voltage having a magnitude responsive to the frequency of said selected channel;
- means for scaling a version of said analog tuning voltage in response to said pulse control signal to produce a combined control signal with the value of scaling being dependent upon the duty cycle of said pulse control signal, and
- means for coupling said combined control signal to said tunable circuit for adjusting the tuning of said tunable circuit.
In a tuning system including input means for receiving a plurality of RF signals corresponding to respective channels and frequency selection means for selecting one of said plurality of RF signals corresponding to a respective selected channel, apparatus for frequency selection comprising:
- a tunable circuit coupled between said input means and an output and cooperating to control frequency characteristics of apparatus coupled between said input means and said output, said tunable circuit including a reactive element having a reactive value determined by magnitude of an analog control signal;
- means for selecting a channel;
- means for providing a digital control signal in response to the frequencies of said selected channel;
- means for converting said digital control signal to a corresponding pulse control signal;
- means for generating an analog tuning voltage having a magnitude responsive to the frequencies of said selected channel;
- means for scaling a version of said analog tuning voltage in response to said pulse control signal to produce a combined control signal with the value of scaling being determined by the pulse control signal;
- means for coupling said combined control signal to said tunable circuit for adjusting the tuning of said tunable circuit,
- said means for scaling including a voltage divider having a first end and a second end;
- means for coupling said version of said analog tuning voltage to said first end;
- and
- means for coupling said pulse control signal to said second end.
Tuning apparatus, comprising:
- a local oscillator signal having a frequency controlled in response to the magnitude of a tuning signal;
- said local oscillator being included in a closed loop which is responsive to digital data representing a desired channel;
- an RF section having a filter tunable responsive to a magnitude of a tuning signal;
- a memory for storing digital data corresponding to frequencies of selected channels;
- means for providing a digital frequency selection signal corresponding to the stored digital data;
- means for converting said digital digital frequency selection signal to a corresponding pulse signal;
- means for generating an analog tuning voltage having a magnitude responsive to the frequencies of said selected channel;
- a voltage divider having a first end and a second end and a point intermediate of said ends;
- means for coupling said pulse signal to said first end;
- means for coupling said second end to a version of the analog tuning voltage;
- and
- means coupled to said intermediate point for developing said tuning signal for tuning said tunable filter.
Dependencies are inferred from the claim text.