Method and apparatus for communication channel identification and signal restoration

• US 5,111,298 A
• Filed: 04/30/1991
• Issued: 05/05/1992
• Est. Priority Date: 10/09/1990
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Inventors: Koo, David
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US07/693,737
• Time in Patent Office: 371 Days
• Field of Search: 358/187, 358/139, 358/167, 358/905, 375/13, 375/15, 375/19, 455/65, 455/67
• US Class Current: 348/614
• CPC Class Codes: H04L 1/242 by comparing a transmitted test signal with a locally generated replica
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0244 with inversion
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence

Abstract

A method and apparatus for improved ghost cancellation for use in particular in television receivers. The sequence of coefficients derived from a received GCR (Ghost Cancellation Reference) signal, is further processed to effect a transfer of energy from minor echo coefficients to major echo coefficients thereby improving the overall performance of the ghost cancellation device.

Claims

1. A method for removing channel induced distortion from signals, comprising the steps of:

a) receiving a test signal after it has passed through and been distorted by a communication channel;

b) deriving from said received test signal a sequence of coefficients to be used with at least one filter;

c) subjecting said sequence of coefficients to a transformation process so as to transform it from its time domain state to its frequency domain state;

d) widening the bond width of said sequence of coefficients in said frequency domain state; and

e) subjecting said widened bandwidth frequency domain state to an inverse transform process so as to transform it into its time domain state.

2. The method of claim 1 wherein said widening step comprises duplicating a plurality of non-zero values within said frequency domain state so as to replace values within said frequency domain state which are equal to zero.

3. An apparatus for removing channel induced distortion from signals, comprising:

a) means for receiving a test signal after it is passed through and been distorted by a communication channel;

b) means for deriving from said received test signal a sequence of coefficients to be used with at least one filter;

c) means for processing said sequence of coefficients so as to transform it from its time domain state to its frequency domain state;

d) means for widening the bandwidth of said sequence of coefficients in said frequency domain state; and

e) means for processing said widened bandwidth frequency domain state into its time domain state.

4. A television receiver comprising the apparatus as claimed in claim 3.

5. An apparatus for substantially eliminating ghosts occurring during the transmission of a television signal, wherein said television signal comprises a ghost cancellation reference signal, said apparatus comprising:

a) means for receiving said television signal and for separating therefrom said ghost cancellation reference signal as distorted by said transmission;

b) means for deriving from said received ghost cancellation reference signal a sequence of coefficients to be used with at least one filter, said sequence of coefficients having at least one first selected component and at least one second selected component;

c) means for transferring energy from said second selected component to said first selected component.