Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1980-12-31
1983-08-02
Chin, Tommy P.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
455182, 455186, 455165, 3581931, 3581951, H04B 116, H04N 550
Patent
active
043970389
ABSTRACT:
A television tuning system employs a frequency synthesizer system for establishing the tuning of the receiver. A programmable frequency divider counter is connected between the output of a reference oscillator and a phase comparator to which the output of the local oscillator in the tuner also is applied. The phase comparator output provides a tuning voltage for controlling the tuning of the local oscillator. A microprocessor is used to control the count of the programmable frequency divider and initially to set a count corresponding to the selected channel in a counter connected between the output of the local oscillator and the phase comparator. The tuning consists of three discrete time periods. First, a settling time to allow channel change transients to settle; second, a short period of forced search at a relatively rapid rate to insure proper tuning; and third, a slower rate of step-by-step correction to accomodate for station drift and the like during reception. This third time period is initiated either by the passage of a fixed length of time following the start of the forced search period or by sensing a preestablished number of changes of state in the output of the frequency discriminator during the forced/search period.
REFERENCES:
patent: 4025953 (1977-05-01), Sideris
patent: 4038689 (1977-07-01), Rzeszewski
patent: 4041535 (1977-08-01), Rzeszewski
patent: 4279035 (1981-07-01), Skerlos
A Microcomputer Controlled Frequency Synthesizer for TV, by Rzeszewski, IEEE Transactions on Consumer Electronics, vol. CE-24, No. 2, May 1978, pp. 145-154.
Microcomputer Tunes and Holds Frequencies, Electronics, vol. 50, No. 20, pp. 46-50.
One Chip Controlled Voltage Synthesizer TV Tuning System, by Sasaki, IEEE Transactions on Consumer Electronics, vol. CE-24, No. 1, Feb. 1978, pp. 57-66.
Chin Tommy P.
Matsushita Electric Corporation of America
Ptak LaValle D.
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