Ghost cancellation reference signal with bessel chirps & PN sequences, & 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-access 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 form 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.

What is claimed is:  
     
         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 signal scan line in each vertical blanking interval said chirp signal precedes said pseudo noise sequence.  
     
     
         3 . A television receiver for use with ghost-cancellation-reference (GCR) signals of a type that include both a chirp and a PN sequence in a selected scan line of the vertical blanking interval of each field, said television receiver comprising: 
 means 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;    means responding to the separated chirp portions of the GCR signals to calculate a discrete Fourier transform (DFT) therefrom;    means responding to that DFT to determine the adjustable filtering weights of the ghost cancellation filter; and    means responding to the separated PN sequences to determine the adjustable filtering weights of the equalization filter.    
     
     
         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 . A television receiver for receiving television signals of a type wherein a composite video signal including a ghost-cancellation reference signal therewithin is transmitted, said ghost-cancellation reference signal including within an active portion of each of selected scan both a chirp signal and a subsequent 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, wherein within each said pair of selected scan lines the two scan lines have respective pseudo noise sequences of opposite sense to each other, wherein successive ones of said selected scan lines occur in successive vertical blanking intervals of said composite video signal, and 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, said television receiver comprising: 
 means for responding to a television signal to supply said composite video signal;    means for additively and subtractively combining selected scan lines in sets of four successive ones of said selected scan lines so as to separate the chirp portions of the GCR signals from a remainder of said composite video signal;    means for additively and subtractively combining selected scan lines in sets of four successive ones of said selected scan lines so as to separate the PN sequence portions of the GCR signals from a 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;    means responding to the separated chirp portions of the GCR signals to calculate a discrete Fourier transform (DFT) therefrom;    means responding to that DFT to determine the adjustable filtering weights of the ghost cancellation filter; and    means responding to the separated PN sequences to determine the adjustable filtering weights of the equalization filter.    
     
     
         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 chirp signals 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 . A television receiver as set forth in  claim 3  wherein said means for separating the chirp and PN sequence portions of the GCR signals from the remainder of the composite video signal comprises: 
 means for selecting scan lines with said GCR signals from the vertical blanking interval of each field;  
 means for additively and subtractively combining selected scan lines in sets of four successive ones of said selected scan lines, so as to separate the chirp portions of the GCR signals from a remainder of the composite video signal; and  
 means for additively and subtractively combining selected scan lines in sets of four successive ones of said selected scan lines, so as to separate the PN sequence portions of the GCR signals from a remainder of the composite video signal.  
 
     
     
         20 . A television receiver for television signals including ghost-cancellation-reference (GCR) signals, said GCR signals being of a type that include a single chirp with pedestal in a selected scan line of the vertical blanking interval of each field, consecutive ones of which chirps alternate being first and second senses in a prescribed pattern, said television receiver comprising: 
 means for responding to a television signal to supply a composite video signal;    means for separating the chirp information from the remainder of said composite video signal, including    means for selecting an even-numbered plurality of said scan lines with chirps from respective ones of said vertical blanking intervals; and    means for combining corresponding samples of said even-numbered plurality of said selected scan lines to generate respective samples of said chirp information without accompanying pedestal;    a ghost cancellation filter; and    means responding to the separated chirp information for computing the adjustable filtering weights of the ghost cancellation filter.    
     
     
         21 . A television receiver as set forth in  claim 20  wherein said means responding to the separated chirp information for computing the adjustable filtering weights of the ghost cancellation filter comprises: 
 means responding to the separated chirp portions of the GCR signals to calculate a discrete Fourier transform (DFT) therefrom; and  
 means responding to that DFT to determine the adjustable filtering weights of the ghost cancellation filter.  
 
     
     
         22 . A television receiver as set forth in  claim 21  wherein said even-numbered plurality of said selected scan lines includes four scan lines.  
     
     
         23 . A television receiver as set forth in  claim 21  wherein said even-numbered plurality of said selected scan lines includes a multiple of four scan lines.  
     
     
         24 . A television receiver as set forth in  claim 20  wherein said even-numbered plurality of said selected scan lines includes four scan lines.  
     
     
         25 . A television receiver as set forth in  claim 20  wherein said even-numbered plurality of said selected scan lines includes a multiple of four scan lines.  
     
     
         26 . A television receiver as set forth in  claim 20  including means for separating information concerning the pedestals of said chirp information, separated from said chirp information, which means comprises: 
 said means for selecting an even-numbered plurality of said scan lines with chirps from respective ones of said vertical blanking intervals, and  
 means for combining corresponding samples of said even-numbered plurality of said selected scan lines to generate respective samples of said information concerning the pedestals of said chirp information, separated from said chirp information.  
 
     
     
         27 . A television receiver for television signals including ghost-cancellation-reference (GCR) signals, said GCR signals being of a type that include a single chirp with pedestal in a selected scan line of the vertical blanking interval of each field, consecutive ones of which chirps alternate being first and second senses in a prescribed pattern, said television receiver including: 
 means for responding to a television signal to supply a composite video signal;    means for separating information concerning the pedestals of said chirp information, separated from said chirp information, which means comprises:    said means for selecting an even-numbered plurality of said scan lines with chirps form respective ones of said vertical blanking intervals, and    means for combining corresponding samples of said even-numbered plurality of said selected scan lines to generate respective samples of said information concerning the pedestals of said chirp information, separated from said chirp information.    
     
     
         28 . A television receiver for television signals including ghost-cancellation-reference (GCR) signals, said GCR signals being of a type that include a single chirp with pedestal in a selected scan line of the vertical blanking interval of each field, consecutive ones of which chirps alternate being first and second senses in a prescribed pattern, said television receiver comprising: 
 means for responding to a television signal to supply a composite video signal;    means for separating the chirp information from the remainder of the composite video signal, including    means for selecting an even-numbered plurality of said scan lines with chirps from respective ones of said vertical blanking intervals, said even-numbered plurality being a multiple of four, each of which selected scan lines includes front porch, horizontal synchronizing pulse, back porch, color burst and a pedestal for the chirp therewithin;    means for combining corresponding samples of said even-numbered plurality of said selected scan lines to generate respective samples of said chirp information without accompanying front porch, horizontal synchronizing pulse, back porch, color burst or pedestal;    a ghost cancellation filter; and    means responding to the separated chirp information for computing the adjustable filtering weights of the ghost cancellation filter.    
     
     
         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 . A ghost-cancellation reference signal included within a composite video signal, said composite video signal having a number of successive scan lines within each field which successive scan lines for purposes of claiming are considered to be consecutively numbered in order of their occurrence, wherein in each vertical blanking interval similar respective portions of said ghost-cancellation reference signal occur within respective active portions of an odd-numbered scan line and an even-numbered scan line.  
     
     
         31 . A ghost-cancellation reference signal as set forth in claim  30  wherein said similar respective portions of said ghost-cancellation reference signal occurring within respective active portions of an odd-numbered scan line and an even-numbered scan line in each vertical blanking interval comprise respective chirp signals.  
     
     
         32 . A ghost-cancellation reference signal as set forth in claim  30  wherein said similar respective portions of said ghost-cancellation reference signal occurring within respective active portions of an odd-numbered scan line and an even-numbered scan line in each vertical blanking interval comprise respective pseudo noise sequences.