Electronic tuning type television receiver

Claim 2

An electronic tuning type television receiver comprising a tuning circuit including a local oscillator whose oscillation frequency is controlled to be variable depending on a voltage applied to a variable capacitance means, signal input means for specifying a selected channel, memory means for storing digital data indicative of tuning voltages corresponding to a plurality of channels respectively so that a tuning voltage corresponding to a selected channel can be applied to said variable capacitance means in said tuning circuit, means for reading out from said memory means the digital data corresponding to the selected channel specified by said signal input means, a D/A converter converting the digital data read out from said memory means to an analog signal which is applied to said variable capacitance means, and a tuning detection circuit for generating a signal when said tuning circuit is tuned to the selected channel, wherein tuning voltage control means are provided for alternately increasing and decreasing, at a predetermined rate, the digital data read out from said memory means to sequentially apply a signal representative of said alternately increased and decreased data to said D/A converter, and for ceasing the increasing and decreasing operation in response to the appearance of an output from said tuning detection circuit.

Claim 3

An electronic tuning type television receiver comprising a tuning circuit including a local oscillator whose oscillation frequency is controlled to be variable depending on a voltage applied to a variable capacitance diode, signal input means for specifying a selected channel, memory means for storing digital data indicative of tuning voltages corresponding to a plurality of channels respectively so that a tuning voltage corresponding to a selected channel can be applied to said variable capacitance diode in said tuning circuit, means for reading out from said memory means the digital data corresponding to the selected channel specified by said signal input means, a D/A converter converting the digital data read out from said memory means to an analog signal which is applied to said variable capacitance diode, and a tuning detection circuit detecting the fact that said tuning circuit is tuned to the selected channel, wherein the improvement comprises tuning voltage control means which functions to sequentially modify, at a predetermined rate, the digital data read out from said memory means to sequentially apply such a signal to said D/A converter, and which ceases its data modifying operation in response to the appearance of an output from said tuning detection circuit, and wherein said tuning voltage control means comprises means for generating a train of clock pulses, counter means starting to count said clock pulses under control of said means for reading out the digital data from said memory means, and arithmetic operation means for adding or subtracting the count of said counter means to or from the digital data read out from said memory means, the output of said arithmetic operation means being applied to said D/A converter.

Claim 4

An electronic tuning type television receiver comprising a tuning circuit including a local oscillator whose oscillation frequency is controlled to be variable depending on a voltage applied to a variable capacitance diode, signal input means for specifying a selected channel, memory means for storing digital data indicative of tuning voltages corresponding to a plurality of channels respectively so that a tuning voltage corresponding to a selected channel can be applied to said variable capacitance diode in said tuning circuit, means for reading out from said memory means the digital data corresponding to the selected channel specified by said signal input means, a D/A converter converting the digital data read out from said memory means to an analog signal which is applied to said variable capacitance diode, and a tuning detection circuit detecting the fact that said tuning circuit is tuned to the selected channel, wherein the improvement comprises tuning voltage control means which functions to sequentially modify, at a predetermined rate, the digital data read out from said memory means to sequentially apply such a signal to said D/A converter, and which ceases its data modifying operation in response to the appearance of an output from said tuning detection circuit, and wherein said tuning voltage control means comprises means for generating a train of clock pulses, counter means starting to count said clock pulses under control of said means for reading out the digital data from said memory means, and arithmetic operation means for adding or subtracting the count of said counter means to or from the digital data read out from said memory means, the output of said arithmetic operation means being applied to said D/A converter.

Claim 5

An electronic tuning type television receiver comprising a tuning circuit including a local oscillator whose oscillation frequency is controlled to be variable depending on a voltage applied to a variable capacitance means, signal input means for specifying a selected channel, memory means for storing digital data indicative of tuning voltages corresponding to a plurality of channels respectively so that a tuning voltage corresponding to a selected channel can be applied to said variable capacitance means in said tuning circuit, means for reading out from said memory means the digital data corresponding to the selected channel specified by said signal input means, a D/A converter converting the digital data read out from said memory means to an analog signal which is applied to said variable capacitance means, a tuning detection circuit generating a signal when said tuning circuit is tuned to the selected channel, means to generate an alternately varying signal to control digital data being read out from said memory to said D/A converter, means to sequentially change the value of said digital data in accordance with said alternately varying signal, and means responsive to said signal at the output of said tuning detection circuit to cease generation of said alternately varying signal.

Claim 6

An electronic tuning type television receiver comprising a tuning circuit including a local oscillator whose oscillation frequency is controlled to be variable depending on a voltage applied to a variable capacitance means, signal input means for specifying a selected channel, memory means for storing digital data indicative of tuning voltages corresponding to a plurality of channels respectively so that a tuning voltage corresponding to a selected channel can be applied to said variable capacitance means in said tuning circuit, means for reading out from said memory means the digital data corresponding to the selected channel specified by said signal input means, a D/A converter converting the digital data read out from said memory means to an analog signal which is applied to said variable capacitance means, a tuning detection circuit generating a signal when said tuning circuit is tuned to the selected channel, means to generate an alternately varying signal to control digital data being read out from said memory to said D/A converter, means to sequentially change the value of said digital data in accordance with said alternately varying signal, and means responsive to said signal at the output of said tuning detection circuit to cease generation of said alternately varying signal.