Apparatus for demodulating and decoding video signals encoded in different formats

• US 5,671,253 A
• Filed: 07/12/1995
• Issued: 09/23/1997
• Est. Priority Date: 07/12/1995
• Status: Expired due to Term

• Current Assignee: Thomson Consumer Electronics Incorporated (Vantiva SA)
• Original Assignee: Thomson Consumer Electronics Incorporated (Vantiva SA)
• Inventors: Stewart, John Sidney
• Primary Examiner(s): BOCURE, TESFALDET
• Application Number:
  US08/501,361
• Time in Patent Office: 804 Days
• Field of Search: 375/261, 375/262, 375/265, 375/266, 375/233, 375/281, 375/326, 375/355, 375/329, 375/330, 375/331, 375/340, 375/341, 375/345, 375/316, 375/332, 348/426, 348/475, 348/724, 348/736, 348/555, 329/304, 455/234.1
• US Class Current: 375/316
• CPC Class Codes: H04L 1/0046 Code rate detection or code type detection H04L1/0038 takes precedence; detection of the data rate H04L25/0262; for packet format H04L1/0091
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2332 using a non-coherent carrier
• CPC Class Codes: H04L 27/3809 Amplitude regulation arrangements
• CPC Class Codes: H04L 27/3854 using a non - coherent carrier, including systems with baseband correction for phase or frequency offset
• CPC Class Codes: H04L 7/0334 Processing of samples having at least three levels, e.g. soft decisions
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• 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 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence

Abstract

An adaptive receiver includes an adaptive demodulator and an adaptive decoder for providing demodulated and decoded output data from a video signal encoded for satellite, terrestrial or cable transmission. The demodulator recovers demodulated output data by using an adaptive timing recovery network and an adaptive carrier recovery network that incorporates a selectable slicer network. In addition, an Automatic Gain Control network within the demodulator provides a gain control output as a function of a difference between signals produced both prior to and following the slicer. The demodulator may also incorporate a signal quality detector that uses carrier recovery network signals to provide an estimate of the error in the demodulated output data. The decoder produces a Viterbi decoded output from the demodulated output data by using a selectable code rate Viterbi decoder.

Claims

1. In a system for receiving and adaptively processing a carrier modulated with video information in one of a plurality of different modulation formats suitable for satellite, terrestrial or cable transmission, an adaptive demodulator network comprising:

a timing recovery network for recovering timing data from said modulated carrier;

an adaptive carrier recovery network responsive to said timing data for recovering said video information from said carrier in said different modulation formats; and

a selectable slicer network, included in said carrier recovery network, for applying a set of decision thresholds to data provided by said carrier recovery network to recover said video information, said set of decision thresholds being selected from a plurality of sets of decision thresholds suitable for said different modulation formats.

2. A system according to claim 1, further including

an Automatic Gain Control (AGC) network providing a gain control output as a function of a difference between a signal produced before said slicer network and a signal produced after said slicer network.

3. A system according to claim 1, further including

a selectable differential decoder for differentially decoding a signal produced by said carrier recovery network.

4. A system according to claim 1, wherein

said selectable slicer network applies decision thresholds appropriate for PAM, QPSK or QAM symbol constellations.

5. A system according to claim 1, wherein

the modulation format of said video information uses a symbol constellation containing a plurality of symbol points.

6. A system according to claim 1, wherein

said carrier recovery network further includes a selectable equalizer network for compensating for errors associated with a transmission channel, wherein the configuration of said equalizer filter network is selected in accordance with the modulation format of said modulated carrier.

7. A system according to claim 6, wherein

said selectable equalizer network includes a Feed Forward Equalizer filter and a Decision Feedback Equalizer.

8. A system according to claim 1, further including

a differential decoder for differentially decoding a signal produced by said carrier recovery network.

9. A system according to claim 1, wherein

said carrier recovery network is capable of operating at different clock rates.

10. A system according to claim 1, further including

a signal quality detector providing as an output an estimate of error occurring in said recovered video information obtained from said different modulation formats.

11. A system according to claim 10, wherein

said adaptive carrier recovery network is automatically configured to be compatible with the modulation format of said video modulated carrier in response to said error estimate.

12. Apparatus according to claim 10, wherein

said estimate of error is a function of the sum of the squares of quadrature components of a signal processed by said carrier recovery network.

13. A system according to claim 10, wherein

said estimate of error is a function of the difference between a first and a second value, wherein

said first value represents the sum of the squares of quadrature components of a signal input to said slicer network and

said second value represents the sum of the squares of quadrature components of an output signal from said slicer network.

14. In a receiver for adaptively processing an input signal containing data in one of a plurality of different input formats and wherein said data is encoded in one of a plurality of different coding formats, apparatus comprising:

an adaptive timing recovery network for recovering timing information from said input signal as a function of a received input signal format;

an adaptive data recovery network responsive to said timing information for recovering said data;

a selectable slicer network, included in said data recovery network, for applying a set of decision thresholds to data provided by said carrier recovery network to recover said data, said set of decision thresholds being selected from a plurality of sets of decision thresholds suitable for said different input formats; and

an adaptive decoder for selectively decoding said recovered data as a function of a received data coding format to produce recovered and decoded output data.

15. Apparatus according to claim 14, further including

a signal quality detector providing as an output an estimate of error occurring in said recovered and decoded output data.

16. Apparatus according to claim 15, wherein

said adaptive receiver is automatically configured to be compatible with said input format in response to said error estimate.

17. Apparatus according to claim 14, wherein

said data is carrier modulation data;

and

said data recovery network is a carrier recovery network for recovering said modulation data.

18. In a receiver for adaptively processing a carrier modulated with data in one of a plurality of different formats suitable for satellite, terrestrial or cable transmission and wherein said modulating data is encoded in one of a plurality of different formats suitable for satellite, terrestrial or cable transmission, apparatus comprising:

an adaptive timing recovery network for recovering timing data from said modulated carrier as a function of a received carrier modulation format;

an adaptive carrier recovery network responsive to said timing data for recovering modulating data from said modulated carrier;

a selectable slicer network, included in said carrier recovery network, for applying a set of decision thresholds to data provided by said carrier recovery network to recover said modulating data, said set of decision thresholds being selected from a plurality of sets of decision thresholds suitable for said different modulation formats; and

an adaptive decoder for selectively decoding said recovered modulating data as a function of a received data encoding format to produce demodulated and decoded output data.

19. Apparatus according to claim 18, further including

a signal quality detector providing as an output an estimate of error occurring in said demodulated and decoded output data.

20. Apparatus according to claim 19, wherein

said adaptive receiver is automatically configured to be compatible with said received carrier modulation format in response to said error estimate.

21. A receiver for adaptively processing a carrier modulated with video data in one of a plurality of different modulation formats and wherein said modulating video data is encoded in one of a plurality of different formats, comprising:

an adaptive timing recovery network for recovering timing data from said modulated carrier as a function of a received carrier modulation format;

an adaptive carrier recovery network responsive to said timing data for recovering modulating data from said modulated carrier;

a selectable slicer network, included in said carrier recovery network, for applying a set of decision thresholds to data provided by said carrier recovery network to recover said modulating data, said set of decision thresholds being selected from a plurality of sets of decision thresholds suitable for said different modulation formats;

an adaptive Viterbi decoder for Viterbi decoding said recovered modulating data and providing a Viterbi decoded output as a function of a received data encoding format;

an adaptive deinterleaver for deinterleaving said Viterbi decoded output and providing an output in accordance with a deinterleaving function selected from a plurality of deinterleaving functions;

an adaptive error processor for error correcting said deinterleaved output to provide an error corrected output; and

a descrambler for descrambling said error corrected output.