Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1988-09-09
1990-05-29
Groody, James J.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 17, H04N 946
Patent
active
049300032
ABSTRACT:
A color synchronizing circuit (120) of a color television receiver includes a PLL circuit having a phase detector circuit (12b), an LPF (12c), a VCO (12d) and a 1/4 frequency divider (12f). Color bursts extracted from a composite chrominance signal by a burst gate circuit (12a) are directly applied to an input of the above described PLL circuit through an adder (12g) in a burst period while being circulated through a loop including a delay circuit (12h) by a switch (12i). The delay circuit has a delay time which is equal to a period of the back porch of a horizontal synchronizing signal having the color burst inserted thereinto and is equal to integer multiples of a cycle of a chrominance subcarrier. Thus, the repetition frequency of the color burst sequentially supplied to the PLL circuit while being circulated through the above described loop becomes 16 times a horizontal frequency f.sub.H. As a result, the sidebands which appear at the intervals of f.sub.H in the frequency spectrum of the color bursts is decreased, so that the capture range of the PLL circuit becomes wide.
REFERENCES:
patent: 4212027 (1980-07-01), Lemoine
Groody James J.
Harvey David E.
Sanyo Electric Co,. Ltd.
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