US 4,380,825 AGranted

Automatic sweep digital tuning circuit

AssigneeMitsubishi Denki Kabushiki Kaisha

InventorsHideharu Takebe, Hiroshi Kobayashi

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Abstract

An automatic sweep digital tuning circuit includes an up-down counter, a digital-to-analog converter, an electronic tuner, an automatic sweep control circuit and an automatic frequency fine control circuit. The up-down counter performs a count-up or count down operation under the control of the automatic sweep control circuit and the automatic frequency fine control circuit. The digital-to-analog converter converts the digital output of the up-down counter into a DC voltage. The electronic tuner receives the DC voltage and generates a tuning frequency. The automatic frequency fine control circuit finely controls the tuning frequency of the electronic tuner after the automatic frequency sweep by the automatic sweep control circuit has been stopped. A count down circuit forces the up-down counter to perform a count down operation to compensate for a time delay caused by the digital-to-analog conversion.

Claims8

Dependent claims

An automatic sweep digital tuning circuit operatively connected to receive a switching signal, comprising:

an automatic sweep control circuit for receiving the switching signal and for generating a pulse signal and a fine control start signal;
an up-down counter, operatively connected to said automatic sweep control circuit, for receiving said pulse signal and for performing a count-up operation to generate a digital output signal;
a digital-to-analog converter, operatively connected to said up-down counter, for converting the digital output signal into an analog signal;
an electronic tuner, operatively connected to said digital-to-analog converter and said automatic sweep control circuit, for receiving said analog signal and for providing a tuning frequency, said automatic sweep control circuit stopping the count-up operation of said up-down counter when the tuning frequency of said electronic tuner approaches a predetermined frequency;
an automatic frequency fine control circuit, operatively connected to said electronic tuner, said automatic sweep control circuit and said up-down counter, for finely controlling the tuning frequency of said electronic tuner in dependence upon said fine control start signal, so that the tuning frequency of said electronic tuner becomes coincident with the predetermined frequency;
and
count down means, operatively connected to said automatic frequency fine control circuit and said automatic sweep control circuit, for providing a count down signal to said automatic frequency fine control circuit in dependence upon said fine control start signal, said automatic frequency fine control circuit causing said up-down counter to perform a count down operation, in dependence upon said count down signal, until the tuning frequency of said electronic tuner is an optimum frequency.

4 more elements

An automatic sweep digital tuning circuit comprising:

switching means for generating a switching signal;
sweep means, operatively connected to said switching means, for receiving said switching signal and for generating a pulse signal and a fine control start signal;
counter means, operatively connected to said sweep means, for receiving said pulse signal and for performing a counting operation to generate a digital output signal;
a digital-to-analog converter, operatively connected to said counter means, for converting the digital output signal into an analog signal;
tuner means, operatively connected to said digital to analog converter and said sweep means, for receiving said analog signal and for generating a tuning frequency signal, said sweep means selectively generating said pulse signal in dependence upon said tuning frequency signal;
count down means, operatively connected to said sweep means, for generating a count down signal in dependence upon said fine control start signal;
and
fine control means, operatively connected to said tuner means, said count down means and said counter means, for generating a count decrease signal in dependence upon said count down signal and for generating a count increase signal in dependence upon said tuning frequency signal, said fine control means controlling the tuning frequency of said tuner means so that the tuning frequency of said tuner means becomes coincidental with an optimum frequency.

5 more elements

Dependencies are inferred from the claim text.