US 6,480,239 B1 · 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-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.

Claims21

Dependent claims

An apparatus for transmitting a television signal divided into a plurality of successive fields for reception by a television receiver including adaptive ghost suppression filtering, each said field consisting of a prescribed number of lines of information, said lines being of uniform respective duration, said apparatus characterized by including:

a reference signal generator for transmitting during a prescribed single line of each of said fields a first ghost-cancellation reference signal and a second ghost-cancellation reference signal different than said first ghost-cancellation reference signal, each of said first and said second ghost-cancellation reference signals being transmitted with a modulation swing less than the maximum modulation swing available but more than half said maximum modulation swing, the relative phases of said first and said second ghost-cancellation reference signals varying from field to field in prescribed pattern to facilitate their separation at said television receiver, said first ghost-cancellation reference signal having a prescribed first duration longer than half a line duration to provide said television receiver sufficient energy for detecting ghosts with long differential delay and low energy to furnish a basis for calculation of adjustments of said adaptive ghost suppression filtering to suppress said ghosts with long differential delay and low energy, and said second ghost-cancellation reference signal having a prescribed second duration shorter than half a line duration to facilitate more rapid calculation of adjustments of said adaptive ghost suppression filtering in said television receiver to suppress ghosts with substantial energy and less differential delay.

A receiver, including adaptive ghost suppression filtering, for receiving a signal transmission over a reception channel, said signal transmission divided into a plurality of successive fields having a prescribed number of lines of information and being of uniform respective duration, said receiver including:

an input for receiving in a prescribed single line of each of said fields a first ghost-cancellation reference signal and a second ghost-cancellation reference signal different than said first ghost-cancellation reference signal, each of said first and said second ghost-cancellation reference signals having a modulation swing less than the maximum modulation swing available but more than half said maximum modulation swing, the relative phases of said first and said second ghost-cancellation reference signals varying from field to field in prescribed pattern to facilitate their separation by said receiver, said first ghost-cancellation reference signal having a prescribed first duration longer than half a line duration to provide said receiver sufficient energy for detecting ghosts with long differential delay and low energy to furnish a basis for calculation of adjustments of said adaptive ghost suppression filtering to suppress said ghosts with long differential delay and low energy, and said second ghost-cancellation reference signal having a prescribed second duration shorter than half a line duration to facilitate more rapid calculation of adjustments of said adaptive ghost suppression filtering in said receiver to suppress ghosts with substantial energy and less differential delay.

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims21