Opposite polarization interference cancellation in satellite communication

• US 6,597,750 B1
• Filed: 11/15/1999
• Issued: 07/22/2003
• Est. Priority Date: 06/19/1998
• Status: Expired due to Term

• Current Assignee: Thomson Licensing Dtv
• Original Assignee: Thomson Licensing SA (Vantiva SA)
• Inventors: McNeely, David Lowell, Ramaswamy, Kumar, Knutson, Paul Gothard
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Lugo, David B.
• Application Number:
  US09/423,868
• Time in Patent Office: 1,345 Days
• Field of Search: 375/347, 375/346, 375/349, 375/350
• US Class Current: 375/347
• CPC Class Codes: H04B 7/002 Reducing depolarization effects
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18523 Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service arrangements specially adapted for satellite broadcast receiving H04H40/90; picture transmission via satellite H04N1/00103; television transmission via satellite H04N7/20
• CPC Class Codes: H04L 1/02 by diversity reception
• CPC Class Codes: H04L 5/04 the signals being represented by different amplitudes or polarities, e.g. quadriplex

Abstract

A system for receiving a plurality of broadcast channels transmitted with different polarizations includes a first demodulator for demodulating a first channel having a first polarization to produce a first demodulated channel signal, and a second demodulator for demodulating a second channel having a second polarization, opposite to the first polarization, to produce a second demodulated channel signal. An adaptive interference cancellation network, coupled to the first and second demodulators, cancels interference, derived from the second channel, in the first demodulated channel signal to produce a received signal.

Claims

1. A system for receiving a plurality of broadcast channels, said broadcast channels being transmitted having different polarizations, comprising:

a first demodulator for demodulating a first channel having a first polarization to produce a first demodulated channel signal;

a second demodulator for demodulating a second channel having a second polarization opposite to the first polarization to produce a second demodulated channel signal; and

an adaptive interference cancellation network, coupled to the first and second demodulators, for canceling interference in one of said first and second demodulated channel signals by means of a decoder for generating decoded symbol data from the other of said demodulated channel signals and an encoder for re-encoding said symbol data for generating an ideal signal for use in interference cancellation of a received signal.

2. The system of claim 1 wherein:

the plurality of broadcast channels are transmitted on respective frequencies in a block of frequencies in which two channels are broadcast on every frequency oppositely polarized with respect to each other; and

the first and second channels are transmitted at the same frequency.

3. The system of claim 2 wherein each broadcast channel is encoded to comprise sequential symbols and the adaptive interference cancellation network comprises:

a decoder, coupled to the second demodulator, to generate a signal representing decoded sequential symbols in the second channel;

an encoder, coupled to the decoder, to generate an ideal signal representing the decoded sequential symbols in the second channel; and

an adaptive combiner, coupled to the first demodulator, and the encoder, for estimating an interference component from the ideal signal representing the second channel in the first channel and canceling the interference component from the first channel.

4. The system of claim 3 wherein the adaptive combiner comprises:

an adaptive filter coupled to the encoder, and responsive to a control signal; and

a summer, coupled to the first demodulator and the adaptive filter for generating the control signal.

5. The system of claim 3 further comprising a second decoder, coupled to the first demodulator, to generate a signal representing decoded sequential signals in the first channel.

6. The system of claim 1 wherein:

the plurality of broadcast channels are transmitted on respective frequencies in a block of frequencies in which channels at adjacent frequencies are oppositely polarized with respect to each other; and

the first channel and the second channel are transmitted at adjacent frequencies.

7. The system of claim 6 further comprising:

a third demodulator for demodulating a third channel frequency adjacent to the first channel and having the second polarization, oppositely polarized with respect to the first polarization, to produce a third demodulated channel signal; and

the adaptive interference cancellation network, is further coupled to the third demodulator, for canceling interference in said first demodulated channel signal to produce a received signal, said interference being derived from said second and third channels.

8. The system of claim 7 wherein each broadcast channel is encoded to comprise sequential symbols and the adaptive interference cancellation network comprises:

a first decoder, coupled to the second demodulator, to generate a signal representing decoded sequential symbols in the second channel;

an first encoder, coupled to the first decoder, to generate an ideal signal representing the decoded sequential symbols in the second channel;

a second decoder, coupled to the third demodulator, to generate a signal representing decoded sequential symbols in the third channel;

an second encoder, coupled to the second decoder, to generate an ideal signal representing the decoded sequential symbols in the third channel; and

an adaptive combiner, coupled to the first demodulator, and the first and second encoders, for estimating an interference component from the respective ideal signals representing the second and third channels in the first channel and canceling the interference component from the first channel.

9. The system of claim 8 wherein the adaptive combiner comprises:

a first adaptive filter, coupled to the first encoder, and responsive to a control signal;

a second adaptive filter, coupled to the second encoder, and responsive to the control signal; and

a summer, coupled to the first demodulator, and the first and second adaptive filters, for generating the control signal.

10. The system of claim 8 further comprising a third decoder, coupled to the first demodulator, to generate a signal representing decoded sequential signals in the first channel.