Frequency drift compensation across multiple broadband signals in a digital receiver system

• US 7,382,838 B2
• Filed: 09/17/2001
• Issued: 06/03/2008
• Est. Priority Date: 09/17/2001
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: Digeo Incorporated (CommScope Holding Company, Inc.)
• Inventors: Peting, Mark
• Primary Examiner(s): Ahn; Sam K
• Application Number:
  US09/955,529
• Publication Number:
  US 20030133530A1
• Time in Patent Office: 2,451 Days
• Field of Search: 375/354, 375/373, 375/375, 375/376, 375/240.16, 375/242, 375/260, 375/262, 375/265, 375/340, 375/341, 325/240.1, 348/699, 348/416.1, 348/725, 348/726, 348/729, 708/445, 714/794, 714/795, 714/796, 360/51
• US Class Current: 375/327
• CPC Class Codes: H04N 21/426 Internal components of the client ; Characteristics thereof H04N5/44 takes precedence
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/6143 involving transmission via a satellite
• CPC Class Codes: H04N 5/455 Demodulation-circuits
• CPC Class Codes: H04N 5/52 Automatic gain control

Abstract

A system and method are described for providing drift compensation for a multimedia receiver which processes multimedia streams from a plurality of satellite transponders and/or cable/broadcast carriers. In one embodiment, the average drift amount for all multimedia signals in a first group of multimedia signals is calculated and, based on the calculation, the drift of the entire group is corrected. This drift is referred to as system drift. In addition, the difference in drift between each individual multimedia signal and the system drift amount is used to correct the individual drift for each multimedia signal.

Claims

1. A multimedia receiver system which provides drift compensation for a plurality of different satellite transponder signals or cable/broadcast signals (multimedia signals) received over a common low-noise block downconverter (LNB) comprising:

a system-level drift calculation logic to calculate an average drift amount among said multimedia signals in a first group of multimedia signals received over a common LNB; and

a system-level drift correction logic to correct drift of each of said first group of multimedia signals based on said average drift amount, wherein said system-level drift calculation logic comprises;

a carrier detection module to measure a carrier frequency of each of said first group of multimedia signals; and

an averager module to calculate said average drift amount difference between each of said measured carrier frequencies and corresponding desired carrier frequencies associated with said multimedia signals.

2. The system as in claim 1 further comprising:

a signal-level drift calculation logic to calculate a difference in drift between each individual multimedia signal and said average drift amount; and

a signal-level drift correction logic to correct drift for said each individual multimedia signal based on said difference.

3. The system as in claim 2 wherein said signal-level drift correction logic is comprised of a numerically controlled oscillator (NCO) to correct drift for each individual multimedia signal based on said difference.

4. The system as in claim 1 further comprising:

additional system-level drift calculation logic to calculate a second average drift amount for a second group of multimedia signals received over a second LNB; and

second system-level drift correction logic to correct drift of each of said multimedia signals in said second group by said second average drift amount.

5. The system as in claim 4 wherein the receiver system includes a front end having a plurality of tuners to provide said first group of multimedia signals, and said system-level drift correction logic comprises a phase-locked loop to perform a system-level frequency adjustment based on said average drift amount, by adjusting a center frequency of each of the tuners at the front end of the receiver.

6. The system as in claim 1 wherein said system-level drift calculation logic comprises:

difference logic to calculate the difference between a desired frequency value and an actual frequency value for each individual multimedia stream; and

an averager to calculate the average difference between said desired frequency values and said actual frequency values.

7. The system as in claim 6 wherein said system-level drift correction logic comprises:

a phase locked loop (PLL) to perform a system-level frequency adjustment based on said average drift amount, said system-level frequency adjustment affecting each of said multimedia signals in said first group.

8. The system as in claim 1 wherein said system-level drift correction logic comprises:

a phase locked loop (PLL) to perform a system-level frequency adjustment based on said average drift amount, said system-level frequency adjustment affecting each of said multimedia signals in said first group.

9. The system as in claim 8 wherein said PLL is comprised of a divide-by-N module for precisely adjusting said system-level frequency responsive to said calculated average drift amount.

10. The system as in claim 9 wherein said PLL further comprises:

a sigma-delta A/D module for removing jitter from an output of said divide-by-N module.

11. An apparatus comprising:

a carrier analysis module to measure a signal characteristic of each of a plurality of satellite transponder signals or cable/broadcast signals (carrier signals) provided by a common LNB;

an averager module to calculate an average difference between each of said measured signal characteristics and respective desired signal characteristics; and

signal correction logic to adjust said signal characteristic for all of said carrier signals responsive to said calculated average difference,

wherein said signal characteristic is a measured frequency of each of said carrier signals and said desired signal characteristic is a specified frequency for each of said carrier signals.

12. The apparatus as in claim 11 further comprising:

individual carrier signal correction logic for correcting said signal characteristic for an individual signal carrier based on a difference between said signal characteristic for said signal carrier and said average difference.

13. The apparatus as in claim 12 further comprising:

individual carrier signal detection logic to measure said difference between said signal characteristic of each of said signal carriers and said average difference.

14. An apparatus comprising:

a carrier analysis module to measure a signal characteristic of each of a plurality of satellite transponder signals or cable/broadcast signals (carrier signals) provided by a common LNB;

an averager module to calculate an average difference between each of said measured signal characteristics and respective desired signal characteristics; and

signal correction logic to adjust said signal characteristic for all of said carrier signals responsive to said calculated average difference, wherein said signal carriers are satellite transponder signals and wherein all of said signal carriers adjusted by said signal correction logic are from the same low noise block downconverter (“

LNB”

).