Mitigation of multipath using ultra wideband DTV overlay signal

• US 6,437,832 B1
• Filed: 10/21/1999
• Issued: 08/20/2002
• Est. Priority Date: 10/21/1999
• Status: Expired due to Term

• Current Assignee: NBC Universal Media LLC (Comcast Corporation)
• Original Assignee: General Electric Company
• Inventors: Hershey, John Erik, Grabb, Mark Lewis, Welles, Kenneth Brakeley II
• Primary Examiner(s): Miller, John
• Assistant Examiner(s): Yenke, Brian P.
• Application Number:
  US09/422,449
• Time in Patent Office: 1,034 Days
• Field of Search: H04/N 1.700, H04/N.521, 348/180, 348/181, 348/607, 348/608, 348/611, 348/614, 348/723, 348/725, 348/729, 348/618, 348/735, 348/192, 348/193, 375/343, 375/346, 375/348, 375/349, 375/350
• US Class Current: 348/614
• CPC Class Codes: H04N 5/211 Ghost signal cancellation H04N23/81 takes precedence

Abstract

DTV broadcast transmission is provided with a ultra wideband overlay signal which is used by suitably equipped DTV receivers to dynamically estimate the channel and allow expeditious and effective mitigation of changing multipath conditions. Periodic correlation peaks are detected in the received overlay signal, and the timing and magnitude of other peaks in the received overlay signal are used to mitigate multipath in the received signal. A DTV receiver that is not equipped to process the overlay transmission will not be significantly affected by the overlay signal.

Claims

1. A method of mitigating multipath in a digital television (DTV) signal comprising the steps of:

adding an ultra wideband overlay signal to an DTV signal at a predetermined power ratio of DTV signal to overlay signal before broadcasting the DTV signal, the ultra wideband overlay signal being centered on a channel of interest and using the spectrum of many adjacent channels;

receiving a transmitted DTV signal;

detecting a periodic correlation peak in the ultra wideband overlay signal;

detecting other peaks in the ultra wideband overlay signal; and

using timing and magnitude of the detected other peaks to mitigate multipath in the received signal.

2. The method of mitigating multipath in a DTV signal recited in claim 1, further comprising the step of generating the ultra wideband overlay signal from a sequence generator.

3. The method of mitigating multipath in a DTV signal recited in claim 2, wherein the sequence generator is adapted to generate a sequence that can be sequentially synchronized.

4. The method of mitigating multipath in a DTV signal recited in claim 1, further comprising the step of subtracting the overlay signal and its multipath components from the received signal.

5. A digital television (DTV) system for mitigating multipath in a DTV signal comprising:

a transmitter;

an adder connected to the transmitter for adding an ultra wideband overlay signal to the DTV signal at a predetermined power ratio of DTV signal to overlay signal before providing the DTV signal with the overlay signal to said transmitter for broadcast, the ultra wideband overlay signal being centered on a channel of interest and using the spectrum of a plurality of adjacent channels; and

a receiver for receiving the DTV signal with the ultra wideband overlay signal, the receiver comprising;

a detector receiving the DTV signal with the ultra wideband overlay signal and detecting periodic correlation peaks in the ultra wideband overlay signal and other peaks in the ultra wideband overlay signal representing multipath, and

an equalizer connected to the detector and responsive to the detector and adapted to use timing and magnitude of detected other peaks to mitigate multipath in the received signal.

6. The DTV system for mitigating multipath in a DTV signal recited in claim 5, further comprising a sequence generator connected to the adder for generating the ultra wideband overlay signal for provision to said adder.

7. The DTV system for mitigating multipath in a DTV signal recited in claim 6, wherein the sequence generator is adapted to generate a sequence that can be sequentially synchronized.

8. The DTV system for mitigating multipath in a DTV signal recited in claim 5, further comprising a summer connected to said receiver for subtracting the overlay signal and its multipath components from the signal received by said receiver.

9. Digital television (DTV) receiving apparatus for mitigating multipath in a DTV signal, comprising:

a receiver receiving a broadcast DTV signal to which has been added an ultra wideband overlay signal at a predetermined power ratio of DTV signal to overlay signal before broadcast, the ultra wideband overlay signal being centered on a channel of interest and using the spectrum of many adjacent channels;

a detector connected to said receiver and detecting periodic correlation peaks in the ultra wideband overlay signal and other peaks in the ultra wideband overlay signal representing multipath; and

an equalizer connected to said detector and responsive to said detector and adapted to employ timing and magnitude of detected other peaks to mitigate multipath in the received broadcast signal.

10. The DTV receiving apparatus for mitigating multipath in a DTV signal recited in claim 9, further comprising a summer connected to said receiver for subtracting the overlay signal and its multipath components from the received broadcast signal.

11. A method of mitigating multipath in a digital television (DTV) signal comprising the steps of:

generating an ultra wideband overlay signal from a sequence generator;

adding the ultra wideband overlay signal to an DTV signal at a predetermined power ratio of DTV signal to overlay signal before broadcasting the DTV signal, the ultra wideband overlay signal being centered on a channel of interest and using the spectrum of many adjacent channels;

receiving a transmitted DTV signal;

detecting a periodic correlation peak in the ultra wideband overlay signal;

detecting other peaks in the ultra wideband overlay signal;

using timing and magnitude of the detected other peaks to mitigate multipath in the received signal; and

subtracting the ultra wideband overlay signal and its multipath components from the received signal.