Line sync detector for digital television receiver

Details Line sync detector for digital television receiver Line sync detector for digital television receiver

1995-09-26

1997-01-14

Lee, Michael H.

Television

Synchronization

Sync separation

348495, 375366, 375368, H04N 704, H04N 1106, H04N 510

Patent

active

055945066

ABSTRACT:
A line sync detector for a digital television receiver receives digital television data including line synchronization code groups of four symbols having successive values of +S, -S, -S and +S at the beginning of each data line, S being a prescribed sample level. A first delay line has an input tap to which the digital television data are supplied, an output tap, first and second intermediate taps, a first symbol latch having an input connection from the input tap and having an output connection to the first intermediate tap, a second symbol latch having an input connection from the first intermediate tap and having an output connection to the second intermediate tap, and a third symbol latch having an input connection from the second intermediate tap and having an output connection to the output tap. The signals at the input tap, the first and second intermediate taps and the output tap of the first delay line are combined in 1:(-1):(-1):1 ratio to generate a combined response. A window detector receives the combined response and generates a response to the combined response whenever successive values of +S, -S, -S and +S occur in the digital television data supplied to the input tap of the first tapped delay line. A correlation filter responds to the response of the window detector for generating a re-inforced response to groups of successive values of +S, -S, -S and +S in the digital television data supplied to the input tap of the first delay line that recur at data line intervals. The reinforced response exhibits peaks when line synchronization code groups occur or are predicted to occur but in fact do not because of noise interference. A threshold detector detects when the reinforced response exceeds a prescribed threshold value in a prescribed polarity, for generating indications of when each line synchronization code group occurs.

REFERENCES:
patent: 4697277 (1987-09-01), van Rassel
patent: 4833694 (1989-05-01), Young et al.
patent: 5416524 (1995-05-01), Citta et al.

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