Apparatus and method for providing digital audio in the FM broadcast band
First Claim
1. A method of broadcasting audio signals, comprising the steps of:
- digitizing a channel of audio source material to produce a compressed digital data stream;
modulating a carrier with said data stream using multilevel modulation to produce an RF channel signal having a bandwidth of no more than about 400KHz and a frequency within the FM radio broadcast band; and
transmitting the RF channel signal in a channel allocation of no more than 400KHz within said FM radio broadcast band.
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0 Petitions
Accused Products
Abstract
Method and apparatus are provided for transmitting, receiving, and reproducing digital audio signals as discrete carriers similar to standard FM broadcast signals. An audio signal is digitized using, for example, adaptive delta modulation techniques. Several channels of audio information, such as left and right stereo channels and a second audio program ("SAP") channel can all be digitized and incorporated onto the digital broadcast signal carrier. The digitized audio signal may be modulated using multiphase modulation of the carrier of an FM broadcast band signal. A plurality of audio channels may be digitized and transmitted over the airwaves, or over a cable transmission network. Channels of nondigitized audio channels may be interspersed with the digitized audio channels. Source material for the digitized audio channels may be provided to a cable headend over the cable transmission network outside the FM band, and rebroadcast over the cable transmission network in the FM band. Advantageously, an "extended" FM band between 72-120 MHz is employed to provide more channels than the "standard" FM band of 88-108 MHz.
170 Citations
35 Claims
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1. A method of broadcasting audio signals, comprising the steps of:
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digitizing a channel of audio source material to produce a compressed digital data stream; modulating a carrier with said data stream using multilevel modulation to produce an RF channel signal having a bandwidth of no more than about 400KHz and a frequency within the FM radio broadcast band; and transmitting the RF channel signal in a channel allocation of no more than 400KHz within said FM radio broadcast band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of rebroadcasting audio signals received from a program source via a cable television transmission line, comprising the steps of:
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receiving audio source material via a cable television transmission line in a band outside of the FM radio broadcast band; processing said audio source material to produce a compressed digital data stream; modulating a carrier with said data stream using multilevel modulation to produce an RF channel signal having a bandwidth of no more than about 400KHz and a frequency within the FM radio broadcast band; and transmitting the RF channel signal in said FM radio broadcast band over said cable television transmission line. - View Dependent Claims (15, 16, 17, 18, 19)
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20. Apparatus for receiving digital and analog audio signals comprising:
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tuner means for tuning to signals in the FM radio broadcast band; digital demodulator means for demodulating a multilevel modulated, compressed digitized audio signal transmitted in a channel allocation of no more than 400KHz in the FM radio broadcast band and output from said tuner; decoder means for processing the demodulated compressed digitized audio signal to provide an audio output signal; and analog demodulator means for demodulating a nondigitized audio signal transmitted in a different channel allocation of about 400KHz in the FM radio broadcast band and output from said tuner to provide an audio output signal. - View Dependent Claims (21, 22, 23)
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24. A radio receiver for providing reproduction of audio signals transmitted as digital data in the FM radio broadcast band comprising:
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a tuner for receiving compressed digital audio signals in channel allocations of no more than 400KHz in the FM band; digital demodulator means coupled to an output of said tuner for demodulating a multilevel modulated, compressed digital audio signal received in the FM band; and decoder means, coupled to receive demodulated compressed digital audio data from said digital demodulator means, for converting the data to an analog audio signal. - View Dependent Claims (25, 26)
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27. Apparatus for broadcasting audio signals, comprising:
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means for digitizing a plurality of channels of audio source material to produce a plurality of compressed digital data streams; means, coupled to said digitizing means, for modulating a plurality of RF carriers with said data streams using multilevel modulation to produce a plurality of digital RF channel signals, each having a bandwidth of no more than about 400KHz and a frequency within the FM radio broadcast band; and means, coupled to said modulating means, for transmitting the digital RF channel signals in said FM radio broadcast band. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34)
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35. A radio receiver for providing reproduction of audio signals transmitted as digital data in the FM radio broadcast band comprising:
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a tuner for receiving compressed digital audio signals transmitted over a cable television transmission line in channel allocations of no more than 400KHz in an expanded FM band from about 72MHz to about 120MHz; digital demodulator means coupled to an output of said tuner for demodulating a multilevel modulated, compressed digital audio signal received in said expanded FM band; and decoder means, coupled to receive demodulated compressed digital audio data from said digital demodulator means, for converting the data to an analog audio signal.
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Specification