Ghost cancellation reference signal with bessel chirps and PN sequences, and TV receiver using such signal

Abstract

Composite ghost cancellation reference (GCR) signals that make available both a chirp and a PN sequence during the same vertical-blanking-interval (VBI) scan line in each successive field facilitate more rapid and efficient calculations of ghost cancellation and of equalization, on a continuing basis. A television receiver for use with such composite GCR signals includes circuitry for separating the chirp and PN sequence portions of the GCR signals from the remainder of the composite video signal, a ghost cancellation filter and an equalization filter connected in cascade to respond to the composite video signal and provided each with adjustable filtering weights, and a computer. Random-acess memory addressed during writing snatches the vertical-blanking-interval scan lines selected to include GCR signals. Sets of four successive ones of the selected scan lines are then additively and subtractively combined to separate the chirp portions of the GCR signals from a remainder of the composite video signal. The sets of selected scan lines are additively and subtractively combined in another way to separate the PN sequence portions of the GCR signals from a remainder of the composite video signal. The computer responds to the separated chirp portions of the GCR signals to calculate a discrete Fourier transform (DFT) therefrom. The computer proceeds from that DFT to determine the adjustable filtering weights of the ghost cancellation filter. The computer thereafter responds to the separated PN sequences to determine the adjustable filtering weights of the equalization filter.

1 . A ghost-cancellation reference signal included within a composite video signal, said ghost-cancellation reference signal including within an active portion of each of selected scan lines both a chirp signal and a pseudo noise sequence.  
   
   
       2 . A ghost-cancellation reference signal included within a composite video signal, said ghost-cancellation reference signal including within an active portion of a single scan line in each vertical blanking interval both a chirp signal and a pseudo noise sequence, wherein within each said single scan line in each vertical blanking interval said chirp signal precedes said pseudo noise sequence.  
   
   
       3 . (canceled)  
   
   
       4 . A ghost-cancellation reference signal as set forth in  claim 1 , wherein within each said selected scan line said chirp signal precedes said pseudo noise sequence.  
   
   
       5 . A ghost-cancellation reference signal as set forth in  claim 4 , wherein in each pair of successive pairs of said selected scan lines both scan lines have respective chirp signals of the same sense as each other, and wherein within each said pair of selected scan lines the two scan lines have respective pseudo noise sequences of opposite sense to each other.  
   
   
       6 . A ghost-cancellation reference signal as set forth in  claim 5 , wherein within each said pair of selected scan lines the two scan lines have respective color bursts of opposite sense to each other.  
   
   
       7 . A ghost-cancellation reference signal as set forth in  claim 6 , wherein the two selected scan lines in each succeeding said pair of selected scan lines have respective chirp signals of opposite sense to the respective chirp signals in the preceding said pair of selected scan lines.  
   
   
       8 . A ghost-cancellation reference signal as set forth in  claim 5 , wherein successive ones of said selected scan lines occur in respective vertical blanking intervals of said composite video signal.  
   
   
       9 . A ghost-cancellation reference signal as set forth in  claim 8 , wherein successive ones of said selected scan lines occur in successive vertical blanking intervals of said composite video signal.  
   
   
       10 . A ghost-cancellation reference signal as set forth in  claim 8 , wherein within each said pair of selected scan lines the two scan lines have respective color bursts of opposite sense to each other.  
   
   
       11 . A ghost-cancellation reference signal as set forth in  claim 10 , wherein the two selected scan lines in each succeeding said pair of selected scan lines have respective chirp signals of opposite sense to the respective chirp signals in the preceding said pair of selected scan lines.  
   
   
       12 . A ghost-cancellation reference signal as set forth in  claim 9 , wherein the two selected scan lines in each succeeding said pair of selected scan lines have respective chirp signals of opposite sense to the respective chirp signals in the preceding said pair of selected scan lines.  
   
   
       13 . (canceled)  
   
   
       14 . A ghost-cancellation reference signal as set forth in  claim 1  wherein a prescribed scan line in each vertical blanking interval corresponds to a respective one of said selected scan lines.  
   
   
       15 . A ghost-cancellation reference signal as set forth in  claim 14 , wherein within each said selected scan line said chirp signal precedes said pseudo noise sequence, wherein in each pair of successive pairs of said selected scan lines both scan lines have respective chirp signals of the same sense as each other, and wherein within each said pair of selected scan lines the two scan lines have respective pseudo noise sequences of opposite sense to each other.  
   
   
       16 . A ghost-cancellation reference signal as set forth in  claim 15 , wherein within each said pair of selected scan lines the two scan lines have respective color bursts of opposite sense to each other.  
   
   
       17 . A ghost-cancellation reference signal as set forth in  claim 16 , wherein the two selected scan lines in each succeeding said pair of selected scan lines have respective chirp signals of opposite sense to the respective chirp signals in the preceding said pair of selected scan lines.  
   
   
       18 . A ghost-cancellation reference signal as set forth in  claim 1 , wherein in each pair of successive pairs of said selected scan lines both scan lines have respective pseudo noise sequences of the same sense as each other, and wherein within each said pair of selected scan lines the two scan lines have chirp signals of opposite sense to each other.  
   
   
       19 - 28 . (canceled)  
   
   
       29 . A ghost-cancellation reference signal included within a composite video signal, said ghost-cancellation reference signal including within an active portion of a single scan line in each vertical blanking interval both a chirp signal and a pseudo noise sequence.  
   
   
       30 - 32 . (canceled)  
   
   
       33 . A composite ghost-cancellation reference signal included within a single scan line of a television signal, said composite ghost cancellation reference signal comprising a first ghost-cancellation reference signal having a first time duration and a second ghost-cancellation reference signal having a second time duration shorter than said first time duration, wherein said second ghost-cancellation signal comprises a pseudo-noise sequence.  
   
   
       34 . A composite ghost-cancellation reference signal included within a single scan line of a television signal, said composite ghost cancellation reference signal comprising a first ghost-cancellation reference signal having a first time duration and a second ghost-cancellation reference signal having a second time duration shorter than said first time duration.  
   
   
       35 . The composite ghost-cancellation reference signal of  claim 34  wherein said second ghost-cancellation reference signal comprises a pseudo-noise sequence.  
   
   
       36 . The composite ghost-cancellation reference signal of  claim 35  wherein said first ghost-cancellation reference signal comprises a chirp signal.