System and Method For Protecting Transmissions of Wireless Microphones Operating in Television Band White Space

• US 20110280413A1
• Filed: 05/13/2010
• Published: 11/17/2011
• Est. Priority Date: 05/13/2010
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Wu, Shiquan, Samarasooriya, Vajira
• Granted Patent: US 8,792,589 B2
• Time in Patent Office: Days
• US Class Current: 381/77
• CPC Class Codes: H03J 1/0091 provided with means for scanning over a band of frequencies H03J1/0058 takes precedence
• CPC Class Codes: H04B 1/76 Pilot transmitters or receivers for control of transmission or for equalising
• CPC Class Codes: H04H 60/41 for identifying broadcast space, i.e. broadcast channels, broadcast stations or broadcast areas
• CPC Class Codes: H04H 60/43 for identifying broadcast channels
• CPC Class Codes: H04N 17/004 for digital television systems
• CPC Class Codes: H04N 5/50 Tuning indicators; Automatic tuning control

Abstract

A wireless microphone system broadcasts a pilot tone at the designated ATSC pilot position in the TV Band channel being used by the wireless microphone system. The pilot tone is a readily detectable waveform transmitted in the ATSC pilot position. The pilot tone can be generated by any one of: a standalone pilot tone generator; a pilot tone generator incorporated into a wireless microphone receiver; or, a pilot tone generator incorporated into a wireless microphone.

Claims

1. A method of protecting transmissions of a wireless microphone system operating in a television (TV) band channel, the method comprising:

broadcasting a pilot tone from the wireless microphone system, the pilot tone being broadcast within a frequency band of the TV Band channel used by the wireless microphone system at a location in the frequency band mandated for an Advanced Television Systems Committee (ATSC) pilot for a DTV broadcast, to permit a TV Band device to detect the pilot tone in order to determine that the TV Band channel is in use by the wireless microphone system.

2. The method as claimed in claim 1 wherein the pilot tone is broadcast by a pilot tone generator of the wireless microphone system.

3. The method as claimed in claim 1 wherein the pilot tone is broadcast by a wireless microphone receiver of the wireless microphone system.

4. The method as claimed in claim 1 wherein the pilot tone is broadcast by a wireless microphone of the wireless microphone system.

5. The method as claimed in claim 1 wherein the pilot tone is a single tone modulated by a modulating sequence {b}={+M, −

M, +M, −

M, +M, −

M, +M . . . } with a predetermined signal period assigned such that a bandwidth of the modulated pilot tone is maintained within a narrowband centered on the location of an Advanced Television Systems Committee (ATSC) pilot for a DTV broadcast.

6. The method as claimed in claim 5 wherein the pilot tone is generated by a vestigial side band (VSB) modulator.

7. The method as claimed in claim 5 wherein the pilot tone is generated by a digital waveform generator.

9. The method as claimed in claim 7 further comprising:

if an energy spike is not present in any one of the selected FFT bins, declaring the TV Band channel available for use by the TV Band device;

else

further down-converting the radio frequency signal to a baseband signal and analyzing the baseband signal in the time domain to determine if the baseband signal contains a DTV field-sync or a DTV segment-sync;

else

correlating the baseband signal with a predetermined waveform known to be broadcast by wireless microphone sites, and if there is a good level of correlation, declaring the TV Band channel in use by a wireless microphone;

else

declaring the TV Band channel available for use by the TV Band device.

10. The method as claimed in claim 9 wherein the predetermined waveform is defined at baseband by the following modulating sequence:

{b}={+M, −

M, +M, −

M, +M, −

M, +M . . . }.

8. A method of determining whether a TV Band channel is available for use by a TV Band device, comprising:

tuning to the TV Band channel;

down-converting a radio frequency signal received on the TV Band channel to yield a down-converted signal;

performing a predetermined number of Fast Fourier Transforms (FFTs) of the down-converted signal and accumulating an energy of respective bins associated with the respective FFTs;

selecting a predetermined number of FFT bins centered at a mandated location of an Advanced Television Systems Committee (ATSC) pilot in the TV Band channel; and

analyzing the selected FFT bins to determine if an energy spike is present in any one of the selected FFT bins.

11. A wireless microphone system, comprising:

a pilot tone generator that generates a pilot tone and broadcasts the pilot tone within a frequency band of a TV Band channel used by the wireless microphone system;

wherein the pilot tone is broadcast at a location in a frequency band designated for an Advanced Television Systems Committee (ATSC) pilot in the TV Band channel, to permit a TV Band device to detect the pilot tone in order to determine whether the TV Band channel is in use by the wireless microphone system.

12. The wireless microphone system as claimed in claim 11 wherein the pilot tone generator is a standalone component of the wireless microphone system.

13. The wireless microphone system as claimed in claim 11 wherein a wireless microphone receiver of the wireless microphone system comprises a band pass filter that removes the pilot tone from a radio frequency signal received by the wireless microphone receiver.

14. The wireless microphone system as claimed in claim 13 wherein the pilot tone generator is a component of the wireless microphone receiver and the wireless microphone receiver further comprises an antenna for broadcasting the pilot tone, and an antenna for receiving the radio frequency signal.

15. The wireless microphone system as claimed in claim 14 wherein the pilot tone generator comprises a vestigial sideband modulator.

16. The wireless microphone system as claimed in claim 14 wherein the pilot tone generator comprises a digital waveform generator.

17. The wireless microphone system as claimed in claim 11 wherein the pilot tone generator is a component of the wireless microphone and the wireless microphone further comprises a signal combiner for combining the pilot tone with an FM signal to provide a combined signal broadcast by the wireless microphone.

18. The wireless microphone system as claimed in claim 17 wherein the pilot tone generator comprises a vestigial sideband (VSB) modulator.

19. The wireless microphone system as claimed in claim 17 wherein the pilot tone generator comprises a digital waveform generator.

20. A wireless microphone receiver, comprising a pilot tone generator adapted to generate a pilot tone modulated with a predetermined waveform and to broadcast the pilot tone at a frequency location designated for an Advanced Television Systems Committee (ATSC) pilot in a TV Band channel used by a wireless microphone system with which the wireless microphone receiver is associated.

21. The wireless microphone receiver as claimed in claim 20 wherein the predetermined waveform is defined at baseband by a modulating sequence {b} wherein:

{b}={+M, −

M, +M, −

M, +M, −

M, +M . . . }.

22. The wireless microphone receiver as claimed in claim 20 further comprising an antenna for broadcasting the pilot tone, and an antenna for receiving frequency modulation (FM) signals generated by a wireless microphone of the wireless microphone system.

23. The wireless microphone receiver as claimed in claim 22 further comprising a pilot tone reject mechanism associated with the antenna for receiving the FM signals generated by the wireless microphone of the wireless microphone system.

24. The wireless microphone receiver as claimed in claim 23 wherein the pilot tone reject mechanism comprises a band pass filter.

25. The wireless microphone system as claimed in claim 20 wherein the pilot tone generator comprises a vestigial sideband (VSB) modulator.

26. The wireless microphone system as claimed in claim 20 wherein the pilot tone generator comprises a digital waveform generator.

27. A pilot tone generator for a wireless microphone system that generates a pilot tone of a predetermined waveform and broadcasts the pilot tone at a frequency location mandated for an Advanced Television Systems Committee (ATSC) pilot in a TV Band channel used by the wireless microphone system.

28. The pilot tone generator as claimed in claim 27 wherein the predetermined waveform is defined at baseband by a modulating sequence {b} wherein:

{b}={+M, −

M, +M, −

M, +M, −

M, +M . . . }.

29. The pilot tone generator as claimed in claim 27 wherein the pilot tone is generated by a vestigial sideband (VSB) modulator.

30. The pilot tone generator as claimed in claim 27 wherein the pilot tone is generated by a digital waveform generator.

34. The wireless microphone as claimed in claim 27 wherein the pilot tone generator comprises a digital waveform generator.

31. A wireless microphone of a wireless microphone system, comprising:

a pilot tone generator adapted to generate a pilot tone modulated by a predetermined waveform at a frequency designated for an Advanced Television Systems Committee (ATSC) pilot in a TV Band channel used by the wireless microphone system;

a signal combiner that combines the pilot tone with a frequency modulation (FM) signal generated by the wireless microphone to create a combined signal; and

a combined signal transmitter that broadcasts the combined signal received by a wireless microphone receiver of the wireless microphone system.

32. The wireless microphone as claimed in claim 31 wherein the predetermined waveform is defined at baseband by a modulating sequence {b} wherein:

{b}={+M, −

M, +M, −

M, +M, −

M, +M . . . }.

33. The wireless microphone as claimed in claim 31 wherein the pilot tone generator comprises a vestigial sideband (VSB) modulator.

35. A TV Band device, comprising a pilot sensor adapted to detect a predetermined waveform broadcast by a wireless microphone system at a frequency location designated for an Advanced Television Systems Committee (ATSC) pilot in a TV Band channel used by the wireless microphone system.

36. The TV Band device as claimed in claim 35 further comprising:

a tuner controlled by the pilot sensor to tune to a particular TV Band channel;

a downconverter that down-converts a signal received on the particular TV Band channel to an intermediate frequency signal;

a digitizer that digitizes the intermediate frequency signal to produce a digitized intermediate frequency signal;

a further downconverter that further down-converts the digitized intermediate frequency signal to produce a second digitized intermediate frequency signal;

a Fast Fourier Transform that transforms the second digitized intermediate frequency signal to determine if the second digitized intermediate frequency signal contains an energy spike that exceeds a predetermined threshold.

37. The TV Band device as claimed in claim 36 further comprising a further downconverter to further down-convert the second intermediate frequency signal to a baseband signal, and an analyzer that analyzes the baseband signal to determine if the baseband signal indicates the presence of an ATSC field-sync or an ATSC segment-sync.

38. The TV Band device as claimed in claim 37 further comprising a correlator that correlates the second digitized intermediate frequency signal with the predetermined waveform to determine whether the particular TV Band channel is in use by the wireless microphone system if the ATSC field-sync and the ATSC segment-sync were not identified.

39. The TV Band device as claimed in claim 38 further comprising a white space manager that receives information from the analyzer and the correlator and determines whether the particular TV Band channel is available for use by the TV Band device.