Multi-frequency differentially encoded digital communication for high data rate transmission through unequalized channels
First Claim
1. Apparatus for encoding a data signal on a plurality of carrier frequencies for transmission over a transmission channel, said apparatus comprising:
- encoding means for differentially encoding a plurality of first digital words into a plurality of second digital words, each of said second digital words being a modulation value corresponding to one of said plurality of first digital words, each said modulation value being a predetermined function of said corresponding first digital word and a different one of said first digital words;
transform means coupled to said encoding means for transforming said plurality of modulation values into a digital signal representative of a plurality of predetermined digital carrier frequencies, each of said plurality of predetermined digital carrier frequencies modulated by a corresponding one of said plurality of modulation values; and
data transfer means coupled to said transform means for coupling said digital signal to a transmission channel and for converting said digital signal to an analog signal for transmission over a transmission channel, said analog signal being a sum of a plurality of modulated predetermined analog carrier frequencies corresponding to said plurality of predetermined digital carrier frequencies.
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Abstract
A differentially encoded digital signal waveform is generated as a discrete time representation of a desired analog signal utilizing multi-frequency modulation techniques. The computational capability of present day, industry-standard microcomputers equipped with a floating point array processor or digital signal processor chip is utilized to perform digital frequency encoding and compute both discrete Fourier transforms and inverse discrete Fourier transforms to provide a transmitter and receiver system utilizing suitably programmed microcomputers coupled by a communications channel.
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Citations
30 Claims
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1. Apparatus for encoding a data signal on a plurality of carrier frequencies for transmission over a transmission channel, said apparatus comprising:
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encoding means for differentially encoding a plurality of first digital words into a plurality of second digital words, each of said second digital words being a modulation value corresponding to one of said plurality of first digital words, each said modulation value being a predetermined function of said corresponding first digital word and a different one of said first digital words; transform means coupled to said encoding means for transforming said plurality of modulation values into a digital signal representative of a plurality of predetermined digital carrier frequencies, each of said plurality of predetermined digital carrier frequencies modulated by a corresponding one of said plurality of modulation values; and data transfer means coupled to said transform means for coupling said digital signal to a transmission channel and for converting said digital signal to an analog signal for transmission over a transmission channel, said analog signal being a sum of a plurality of modulated predetermined analog carrier frequencies corresponding to said plurality of predetermined digital carrier frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Apparatus for encoding a signal for transmission over a transmission channel comprising:
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receiving means for receiving a first signal representing digital information, said first signal comprising a plurality of first digital words of equal length; differential encoding means coupled to said receiving means for forming a plurality of modulation states, each of said modulation states associated with a different one of said first digital words, each of said modulation states being a predetermined function of the difference between its associated first digital word and a preceding one of said first digital words; modulating means coupled to said differential encoding means for generating a plurality of modulation values, each of said modulation values corresponding to a different one of said plurality of modulation states, each of said modulation values for modulating a corresponding different one of a plurality of predetermined digital carrier frequencies, said plurality of predetermined digital carrier frequencies being a set of orthogonal carrier frequencies; transform means coupled to said modulating means for transforming said plurality of modulation values into a digital signal representative of said plurality of predetermined digital carrier frequencies, each of said predetermined digital carrier frequencies being modulated by a corresponding modulation value; and data transfer means coupled to said transform means for coupling said digital signal to a transmission channel and for converting said digital signal to an analog signal for transmission over a transmission channel, said analog signal being a sum of a plurality of modulated predetermined analog frequencies corresponding to said plurality of predetermined digital carrier frequencies. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method for encoding a signal for transmission over a transmission channel comprising the steps of:
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receiving a signal representative of digital information, said signal comprising a plurality of first digital words of equal word length; differentially encoding each of said first digital words into a plurality of second digital words, each of said second digital words being a modulation value corresponding to a different one of said plurality of first digital words, each said modulation value being a predetermined function of said corresponding first digital word and a different one of said first digital words; transforming said plurality of second digital words into a digital signal representative of a plurality of predetermined digital carrier frequencies, each of said plurality of predetermined digital carrier frequencies being modulated by a corresponding modulation value; and converting said digital signal to an analog signal for transmission over a transmission signal, said analog signal being a sum of a plurality of modulated analog carrier frequencies corresponding to said plurality of predetermined digital carrier frequencies. - View Dependent Claims (18, 19, 20, 21)
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22. A communications system for transmitting an analog encoded signal utilizing multi-frequency modulation techniques, comprising:
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transmitter means for generating and transmitting a modulated, multi-frequency carrier signal including means for receiving an information signal and converting said information signal to a first digital signal comprising a plurality of first digital words of equal length, differential encoding means for differentially encoding said first digital signal into a plurality of modulation states, each of said modulation states associated with a different word of said first digital words, each of said modulation states being a predetermined function of said associated first digital word and a preceding first digital word, modulation means coupled to said differential encoding means for generating a plurality of modulation values, each of said modulation values corresponding to a different one of said plurality of modulation states, each of said modulation values for modulating a corresponding different one of a plurality of predetermined digital carrier frequencies, said plurality of modulation values forming a set of second digital words, first transform means coupled to said modulating means for transforming said set of second digital words into a second digital signal representative of said plurality of predetermined digital carrier frequencies, each of said predetermined digital carrier frequencies being modulated by a corresponding modulation value; data transfer means coupled between said transmitter means and a transmission means for converting said second digital signal to an analog signal and for transferring said analog signal to said transmission means, said analog signal being a sum of a plurality of modulated predetermined analog carrier frequencies corresponding to said plurality of predetermined digital carrier frequencies, said analog signal transmitted by said transmission means; signal acquisition means coupled to said transmission means for acquiring said transmitted analog signal and converting said transmitted analog signal to a third digital signal; and receiver means coupled to said signal acquisition means for receiving said third digital signal, said receiver means including decoding means for decoding said third digital signal to a digital information signal representative of the information represented by said first digital signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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Specification