Digital wireless speaker system

• US 5,832,024 A
• Filed: 03/26/1997
• Issued: 11/03/1998
• Est. Priority Date: 11/22/1994
• Status: Expired due to Fees

• Current Assignee: LS Research, LLC (Laird Limited)
• Original Assignee: L.S. Research, Inc.
• Inventors: Steinike, William R., Wolski, Mark R., Schotz, Larry
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Liu, Shuwang
• Application Number:
  US08/826,360
• Time in Patent Office: 587 Days
• Field of Search: 375/200, 375/206, 375/209, 375/367, 370/324, 370/209, 381/14, 381/3, 348/525, 340/825
• US Class Current: 375/134
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04H 20/61 for local area broadcast, e.g. instore broadcast
• CPC Class Codes: H04H 20/63 to plural spots in a confined site, e.g. MATV [Master Antenna Television]
• CPC Class Codes: H04H 20/71 Wireless systems
• CPC Class Codes: H04H 60/13 Arrangements for device control affected by the broadcast information
• CPC Class Codes: H04H 60/92 for local area
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04M 1/6066 including a wireless connection
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 5/04 Circuit arrangements, e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments combinations of amplifiers H03F3/68; stereophonic systems H04S

Abstract

This invention discloses a digital wireless speaker system for use in consumer audio applications. A digital radio frequency transmitter is connected to an analog or digital audio source and a digital radio frequency receiver provides for reception of the transmitted audio information in remote locations. In addition, the digital receiver will be able to receive control information to implement such things as volume, tone controls, or other auxiliary information. This allows the user to listen to high quality audio in a variety of locations without the need of independent stereos or external wires. The system is based on digital circuitry to improve the performance of the system and provide for compact disc quality sound. The digital circuitry incorporates forward error correction techniques and interleaving to enable the system to account for errors in transmission and thus improve the overall performance of the system.

Claims

1. A high fidelity, wireless transmission, stereo audio system for use with at least one audio source which provides an audio input signal, said audio system arranged for wirelessly transmitting over the air an electrical signal, susceptible to RF dropout, representing said audio input signal, said stereo audio system comprising:

a transmitter arranged to be coupled to said at least one audio source and comprising;

input means for converting said audio input signal into a first digital serial bit stream signal at a high digital audio bit rate, said first digital serial bit stream signal comprising a first embedded synchronization signal for distinguishing left and right audio data in said audio input signal;

forward error correction encoding means for encoding error correction into said first digital serial bit stream signal to produce an encoded digital serial bit stream signal at the high digital audio bit rate, said encoded digital serial bit stream signal comprising a second embedded synchronization signal detectable by a receiver decoder for initiating decoding;

convolutional interleaving means for interleaving said encoded digital serial bit stream signal and for introducing a third embedded synchronization signal therein to form a second digital serial bit stream signal at the high digital audio bit rate, said third embedded synchronization signal being detectable by a receiver deinterleaver for initiating deinterleaving;

carrier signal producing means for producing a carrier signal of a predetermined frequency of at least 2.4 GHz;

modulation means for modulating said carrier signal with said second digital serial bit stream signal to produce a modulated carrier signal;

first antenna means for emitting over the air said modulated carrier signal at a power level not exceeding approximately 1 milliwatt; and

a receiver located within a range of approximately 10 to 300 feet (3 to 90 meters) of said transmitter and being coupled to an audio transducing device, said receiver receiving and demodulating said modulated carrier signal into an audio output signal.

2. The system of claim 1 wherein said receiver comprises:

a second antenna means for receiving said modulated carrier signal radiated from said first antenna;

demodulation means for demodulating said modulated carrier signal into a demodulated digital signal;

data clock recovery means for recovering a clock from said demodulated digital signal;

convolutional deinterleaving means for deinterleaving said demodulated digital signal in accordance with said third embedded synchronization signal to form a deinterleaved digital serial bit stream signal, said demodulated digital signal being inputted to said deinterleaving means in accordance with said clock;

forward error correction decoding means for correcting errors in said deinterleaved digital serial bit stream signal to form a digital audio signal, said forward error correction decoding means operating upon detection of said second embedded synchronization signal;

output means for converting said digital audio signal into said audio output signal having a format compatible with the audio transducing device, said output means outputting the left and right audio data to the audio transducing device upon detection of said first embedded synchronization signal.

3. The system of claim 1 wherein said input means comprises a digital interface transmitter, said digital interface transmitter receiving a digital audio interface input and converting said digital audio interface input into said first digital serial bit stream signal, said digital interface transmitter inserting said first embedded synchronization signal into said first digital serial bit stream signal.

4. The system of claim 3 wherein said input means further comprises a microprocessor, said microprocessor transmitting subcode information to said digital interface transmitter for introducing said subcode information into said digital serial bit stream signal.

5. The system of claim 4 further comprising a plurality of audio sources coupled to said transmitter, each source providing a respective audio input signal, and wherein said input means further comprises switching means for selecting one of said respective audio input signals to be processed by said digital interface transmitter.

6. The system of claim 5 wherein said one of said respective audio input signals comprises an analog left audio channel signal and an analog right audio channel signal.

7. The system of claim 5 wherein said one of said respective audio input signals comprises an optical audio signal.

8. The system of claim 5 wherein said one of said respective audio input signals comprises a digital audio signal from an RCA connector.

9. The system of claim 1 wherein said carrier signal producing means comprises:

an oscillator;

a phase-locked loop;

a manually-adjustable house code select switch; and

a microprocessor having means for storing digital information representing a plurality of available carrier frequencies, said house code select switch directing said microprocessor to a portion of said digital information representing a particular carrier frequency of at least 2.4 GHz and said microprocessor transmitting said portion to said phase-locked loop for controlling said oscillator.

10. The system of claim 9 wherein said phase-locked loop comprises a synthesizer, said synthesizer being connected to said oscillator, and having means for varying the frequency of said oscillator to produce said carrier signal of a predetermined frequency of at least 2.4 GHz.

11. The system of claim 5 wherein said input means further comprises an adjustable transmitter clock, said clock being adjustable to correspond to said one of said respective audio input signals.

12. The system of claim 7 or claim 8 wherein said input means further comprises a clock synchronization circuit for converting said optical audio signal or said digital audio signal from said RCA connector into a digital audio interface signal.

13. The system of claim 2 wherein said demodulation means generates a first intermediate frequency signal and a second intermediate frequency signal.

14. The system of claim 13 wherein said demodulation means comprises:

a first oscillator;

a phase-locked loop;

a manually-adjustable house code select switch; and

a microprocessor having means for storing digital information representing a plurality of available carrier frequencies, said house code select switch directing said microprocessor to a portion of said digital information representing a particular carrier frequency of at least 2.4 GHz and said microprocessor transmitting said portion to said phase-locked loop for controlling said first oscillator.

15. The system of claim 14 wherein said phase-locked loop comprises a synthesizer, said synthesizer being connected to and having a means for varying the frequency of said first oscillator to produce a first local oscillator signal.

16. The system of claim 15 wherein said demodulation means further comprises a first mixer for mixing said first local oscillator signal with said modulated carrier signal to generate said first intermediate frequency signal.

17. The system of claim 16 wherein said digital demodulation means further comprises:

a second oscillator of a constant frequency which produces a second local oscillator signal; and

a second mixer for mixing said second local oscillator signal with said first intermediate frequency signal to generate said second intermediate frequency signal.

18. The system of claim 1 wherein said modulation means further comprises a quadrature-phase shift keying modulation means for modulating said carrier signal with said second digital serial bit stream signal.

19. The system of claim 1 wherein said modulation means further comprises a binary-phase shift keying modulation means for modulating said carrier signal with said second digital serial bit stream signal.

20. The system of claim 2 wherein said forward error correction decoding means comprises means for muting said deinterleaved digital serial bit stream signal whenever said signal is invalid.

21. The system of claim 20 wherein said forward error correcting decoding means further comprises means for transmitting error information to said output means.

22. The system of claim 21 wherein said output means comprises a digital interface receiver, said digital interface receiver receiving said digital audio signal containing subcode information and converting said digital audio signal into a digital audio interface signal, said digital interface receiver converting said digital audio interface signal into left and right audio data upon detection of said first embedded signal.

23. The system of claim 22 wherein said output means further comprises a microprocessor, said microprocessor receiving said error information for controlling said digital interface transmitter to either interpolate or mute said digital audio interface signal.

24. The system of claim 22 wherein said microprocessor receives said subcode information from said digital interface transmitter and controls said digital interface transmitter to implement said subcode information into said digital audio signal.

25. A high fidelity, wireless transmission, stereo audio system for use with at least one audio source which provides an audio input signal, said audio system arranged for wirelessly transmitting over the air an electrical signal, susceptible to RF dropout, representing said audio input signal, said stereo audio system comprising:

a transmitter arranged to be coupled to said at least one audio source and comprising;

input means for converting and compressing said audio input signal into a digital serial bit stream signal at a high digital audio bit rate, said first digital serial bit stream signal comprising a first embedded synchronization signal for distinguishing left and right audio data;

forward error correction encoding means for encoding error correction into said first digital serial bit stream to produce an encoded signal at the high digital audio bit rate, said encoded signal comprising a second embedded synchronization signal detectable by a receiver decoder for initiating decoding;

convolutional interleaving means for interleaving said encoded signal and for introducing a third embedded synchronization signal therein to form said digital serial bit stream signal at the high digital audio bit rate, said third embedded synchronization signal being detectable by a receiver deinterleaver for initiating deinterleaving;

carrier signal producing means for producing a carrier signal of at least 2.4 GHz;

frequency hopping modulation means for modulating said carrier signal with said digital serial bit stream signal to produce a modulated carrier signal;

first antenna means for emitting over the air said modulated carrier signal at a power level not exceeding approximately 1 watt; and

a receiver located within a range of approximately 10 to 300 feet (3 to 90 meters) of said transmitter and being coupled to an audio transducing device, said receiver receiving and demodulating said modulated carrier signal into an audio output signal.

26. The system of claim 25 wherein said receiver further comprises:

convolutional deinterleaving means for deinterleaving said demodulated digital signal in accordance with said third embedded synchronization signal to form a deinterleaved digital serial bit stream signal, said demodulated digital signal being inputted to said deinterleaving means in accordance with said clock; and

forward error correction decoding means for correcting errors in said deinterleaved digital serial bit stream signal to form said audio output signal, said forward error correction decoding means operating upon detection of said second embedded synchronization signal.

27. The system of claim 26 further comprising a plurality of audio sources coupled to said transmitter, each source providing a respective audio input signal, and wherein said input means further comprises switching means for selecting one of said respective audio input signals to be converted into said digital serial bit stream.

28. The system of claim 27 wherein said one of said respective audio input signals comprises an analog left audio channel signal and an analog right audio channel signal.

29. The system of claim 27 wherein said one of said respective audio input signals comprises an optical audio signal.

30. The system of claim 27 wherein said one of said respective audio input signals comprises a digital audio signal from an RCA connector.