Vertical drive generator and horizontal rate gate generator for a television receiver
AssigneeZenith Radio Corporation
InventorGopal K. Srivastava
Life of this patent
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Abstract
A vertical drive generator and a horizontal gating generator are described which time-share circuitry common to both generators to provide vertical drive pulses and horizontal gating pulses for use in a television receiver. The vertical drive generator converts variable width vertical rate pulses to constant width vertical drive pulses in a manner such that the duration of each drive pulse is determined by a digital counter. In the interval between the generation of successive vertical drive pulses, the counter is reset to provide timing control for the gating generator. In the preferred embodiment, the latter generator develops AGC gating pulses and burst gating pulses at selected times and for selected durations.
Claims10
In a television receiver which develops flyback pulses and variable width vertical rate pulses, and which includes a clock generator and signal processing circuitry requiring gating at a horizontal line rate, a vertical drive generator for converting the vertical rate pulses to constant width vertical drive pulses, combined with a gate generator for gating the signal processing circuitry at a horizontal line rate, comprising:
- vertical drive means responsive to a variable width vertical rate pulse for initiating a vertical rate drive pulse and for generating a counter-enabling signal;
- a counter receiving clock pulses from the clock generator and responsive to the counter-enabling signal for counting the clock pulses;
- decoding means responsive to said counter reaching a given count for disabling said vertical drive means such that the vertical drive pulse is terminated, whereby the width of the vertical drive pulse corresponds to the interval required for the counter to reach said given count, irrespective of the width of the vertical rate pulse;
- a timing signal generator receiving flyback pulses and responsive to the termination of the vertical drive pulse for causing the counter to begin counting anew from an initial count upon receipt of each flyback pulse which occurs subsequent to the termination of the vertical drive pulse,
- at least one gating means adapted to be enabled subsequent to the termination of the vertical drive pulse and responsive to the counter reaching a first predetermined count above its initial count for initiating a gate pulse, and responsive to the counter reaching a second predetermined count above the first count for terminating the gate pulse so that the gate generator develops a gate pulse of a predetermined duration for each flyback pulse which occurs subsequent to the termination of the vertical drive pulse.
In a television receiver which develops flyback pulses and variable width vertical rate pulses, and which includes a clock generator and signal processing circuitry requiring AGC and burst gates at a horizontal line rate, a vertical drive generator for converting the vertical rate pulses to constant width vertical drive pulses, combined with a gate generator for gating the signal processing circuitry at a horizontal line rate, comprising:
- a counter for counting clock pulses developed by the clock generator;
- vertical drive generating means for enabling the counter in response to a variable width vertical rate pulse, for disabling the counter after it has attained a given count, and for generating a constant width vertical drive pulse whose duration corresponds to the time required for the counter to attain said given count;
- reset timing means for enabling the counter to begin counting anew from an initial count subsequent to the generation of the vertical drive pulse;
- an AGC gate generator adapted to be enabled during flyback pulse intervals which occur subsequent to the vertical drive pulse, and responsive to the counter counting to first and second predetermined counts higher than said initial count for generating an AGC gate pulse whose duration corresponds to the time during which said counter counts from said first to said second predetermined counts;
- a burst gate generator, adapted to be enabled during flyback pulse intervals which occur subsequent to the vertical drive pulse, and responsive to the counter counting to third and fourth predetermined counts higher than said initial count for generating a burst gate pulse whose duration corresponds to the time during which said counter counts from said third to said fourth predetermined counts;
- and
- means responsive to said counter attaining a counter higher than said fourth predetermined count for resetting said timing means such that the counter is reset to its initial count.
Dependencies are inferred from the claim text.