Carrier phase synchronization system for improved amplitude modulation and television broadcast reception

• US 7,881,416 B2
• Filed: 07/23/2009
• Issued: 02/01/2011
• Est. Priority Date: 05/17/2001
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Smith, Stephen F., Moore, James A.
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US12/508,330
• Publication Number:
  US 20090296856A1
• Time in Patent Office: 558 Days
• Field of Search: 375/145, 375/149, 375/268, 375/320, 375/327, 375/356, 375/376
• US Class Current: 375/354
• CPC Class Codes: H03D 3/248 with means for eliminating interfering signals, e.g. by multiple phase locked loops multiple loops in general H03L7/07, H03L7/22
• CPC Class Codes: H04H 20/12 Arrangements for observation, testing or troubleshooting
• CPC Class Codes: H04H 20/49 for AM stereophonic broadcast systems
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/06 Demodulator circuits; Receiver circuits

Abstract

Systems and methods are described for carrier phase synchronization for improved AM and TV broadcast reception. A method includes synchronizing the phase of a carrier frequency of a broadcast signal with the phase of a remote reference frequency. An apparatus includes a receiver to detect the phase of a reference signal; a phase comparator coupled to the reference signal-phase receiver; a voltage controlled oscillator coupled to the phase comparator; and a phase-controlled radio frequency output coupled to the voltage controlled oscillator.

Claims

1. A method for synchronizing carrier phases of a group of co-channel amplitude-modulated broadcast signals, the method comprising:

feeding a reference phase output from a multichannel receiver to a phase lock loop;

substantially eliminating audible and sub-audible beats between a local desired station'"'"'s carrier signal and one or more distant interfering stations'"'"' carriers; and

maintaining a predetermined phase relationship between a local desired station'"'"'s carrier signal and one or more distant interfering stations'"'"' carriers.

2. The method of claim 1, wherein synchronizing comprises repetitively synchronizing.

3. The method of claim 2, wherein repetitively synchronizing comprises continuously synchronizing.

4. The method of claim 1, wherein the group of co-channel amplitude-modulated broadcast signals comprises amplitude-modulated analog audio broadcast signals, amplitude-modulated stereo audio broadcast signals, digital audio broadcast signals, amplitude-modulated analog television broadcast signals, amplitude-modulated digital television broadcast signals, or combinations thereof.

5. The method of claim 1, wherein synchronizing the phase of carrier frequencies of the group of co-channel amplitude-modulated broadcast signals comprises synchronizing the phase of carrier frequencies of the group of co-channel amplitude-modulated broadcast signals to the phase of a remote reference frequency.

6. The method of claim 5, wherein synchronizing the phase of carrier frequencies of the group of co-channel amplitude-modulated broadcast signals to the phase of a remote reference frequency includes synchronizing the phase of carrier frequencies of the group of co-channel amplitude-modulated broadcast signals to the phase of a common remote source.

7. The method of claim 5, wherein the remote reference phase includes the phase of a demodulated reference signal.

8. The method of claim 5, wherein synchronizing includes dividing the remote reference frequency, comparing the divided remote reference frequency to a divided carrier-frequency signal and adjusting a phase of the divided carrier-frequency signal to approach a phase of the divided remote reference frequency.

9. The method of claim 5, wherein synchronizing includes comparing the remote reference frequency to a local reference frequency, adjusting a phase of the local reference frequency to approach a phase of the remote reference frequency, dividing the local reference frequency, comparing the divided local reference frequency to a divided carrier -frequency signal and adjusting a phase of the divided carrier-frequency signal to approach a phase of the divided local reference frequency.

10. The method of claim 5, wherein synchronizing includes comparing the remote reference frequency to a local reference frequency, adjusting a phase of the local reference frequency to approach a phase of the remote reference frequency, multiplying the local reference frequency and controlling a numerically controlled oscillator with the multiplied local reference frequency.

11. The method of claim 5, further comprising deriving the remote reference signal phase from at least one source selected from the group consisting of GPS satellites, GOES satellites, LORAN-C, OMEGA, WWVB, WWV, WWVH, CHU, and CDMA cell-phone base stations.

12. The method of claim 5, further comprising deriving the remote reference signal phase from a digital data network.

13. The method of claim 5, further comprising synchronizing the phase of another carrier frequency of another broadcast signal with the phase of the remote reference frequency, wherein both the carrier frequency and the another carrier frequency are of a same nominal frequency.

14. The method of claim 13, further comprising modulating both the carrier of the broadcast signal and the another carrier of the another broadcast signal with a common audio program feed.

15. The method of claim 14, further comprising equalizing the control of the carrier average phase of the broadcast signal and the control of the another carrier average phase of the another broadcast signal.

16. The method of claim 15, wherein the modulation of the carrier of the broadcast signal and the modulation of the another carrier of the another broadcast signal are substantially equally delayed from a central network source.

17. The method of claim 16, further comprising augmenting at least one member selected from the group consisting of the broadcast signal and the another broadcast signal with a repeater of the same nominal frequency and a predetermined phase.

18. In a computer readable storage medium having stored therein data representing instructions executable by a computer system processor, the storage medium comprising instructions operative for:

synchronizing the phase of a carrier frequency of a broadcast signal with the phase of a remote reference frequency;

synchronizing the phase of another carrier frequency of another broadcast signal with the phase of the remote reference frequency, wherein both the carrier frequency and the another carrier frequency are of a same nominal frequency;

modulating both the carrier of the broadcast signal and the another carrier of the another broadcast signal with a common audio program feed, wherein the modulation of the carrier of the broadcast signal and the modulation of the another carrier of the another broadcast signal are substantially equally delayed from a central network source;

augmenting at least one of the broadcast signal or the another broadcast signal, with a repeater of the same nominal frequency; and

monitoring a master skywave signal from the central network source.

19. The method of claim 18, wherein monitoring the master skywave signal includes monitoring an average phase, an average amplitude, an average delay of the master skywave signal, or combinations thereof.

20. The method of claim 18, wherein monitoring the master skywave signal includes using at least one diversity reception technique, selected from the group consisting of spatial diversity, polarization diversity, and time diversity.

21. A method comprising:

detecting the phase of a first reference signal with a first multichannel receiver;

outputting a first amplitude-modulated radio-frequency output with a first voltage-controlled oscillator;

detecting the phase of a second reference signal with a second multichannel receiver;

outputting a second amplitude-modulated radio-frequency output with a second voltage-controlled oscillator,

providing a group of co-channel signals from the first amplitude-modulated radio-frequency output and the second amplitude-modulated radio-frequency output; and

synchronizing carrier frequencies and phases of the group of co-channel signals to;

(a) substantially eliminate audible and sub-audible beats between a local desired station'"'"'s carrier signal and one or more interfering stations'"'"' carriers; and

(b) substantially reduce distortion effects in the signals as received in the coverage area overlapped by the two or more signals.

22. The method of claim 21, wherein a first phase comparator is coupled to the first multichannel reference signal receiver, and the first voltage-controlled oscillator is coupled to the first phase comparator.

23. The method of claim 22, wherein a second phase comparator is coupled to the second multichannel reference signal receiver, and the second voltage-controlled oscillator is coupled to the second phase comparator.