High speed binary data communication system
First Claim
1. A high speed data transmission system for transmitting a binary data signal over a communications path, said binary data signal clocked at a given period, comprising:
- encoding means responsive to a binary NRZ input data signal to provide at an output an encoded digital signal having time periods greater than multiples of said clock period and at a given bit rate whereby said encoded signal occupies a lesser effective bandwidth than said NRZ signal alone, said lesser effective bandwidth being 1/2 to 1/3 that of said NRZ signal;
balanced modulator means having an input responsive to said encoded signal and another input adapted to receive a carrier frequency signal to provide at an output a double sideband suppressed carrier signal shifting in phase 180 degrees with changes in said encoded signal;
filtering means coupled to said output of said balanced modulator to provide a narrow bandwidth less than 1/2 the maximum bandwidth of said sideband signal and by which said carrier frequency and low frequencies are prevented from propagating to reject all sideband frequency components which are lower than 1/4 the bit rate and which are higher than 1/2 the bit rate of said encoded signal to provide at an output a narrow sideband signal for transmission characterized in that transitions between binary levels in said encoded signal are manifested by distinct phase changes in said single sideband signal, said filtering means operative to minimize phase distortion within the sideband signal, while passing only a part of one of said sidebands.
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Abstract
There is disclosed a high speed data transmission system for transmitting a binary data signal over a communications path. The binary data signal is clocked at a given period. The system comprises encoded means responsive to a binary NRZ input data signal to provide at an output an encoded digital signal having time periods greater than multiples of the clock period, whereby the encoded signal occupies a lesser effective bandwidth than the NRZ signal would occupy. There are balanced modulator means having an input responsive to the encoded signal and another input adapted to receive a carrier frequency to provide at an output a double sideband suppressed carrier signal. Coupled to the output of the balanced modulator are narrow bandwidth filtering means including first low pass and second high pass parallel filter paths each having a common input terminal coupled to the output of the modulator. The ouputs of the low and high pass filters are symmetrically combined to provide a narrow single sideband signal for transmission characterized in that transitions between binary levels in said encoded signal are manifested by distinct phase changes in said single sideband signal.
143 Citations
19 Claims
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1. A high speed data transmission system for transmitting a binary data signal over a communications path, said binary data signal clocked at a given period, comprising:
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encoding means responsive to a binary NRZ input data signal to provide at an output an encoded digital signal having time periods greater than multiples of said clock period and at a given bit rate whereby said encoded signal occupies a lesser effective bandwidth than said NRZ signal alone, said lesser effective bandwidth being 1/2 to 1/3 that of said NRZ signal; balanced modulator means having an input responsive to said encoded signal and another input adapted to receive a carrier frequency signal to provide at an output a double sideband suppressed carrier signal shifting in phase 180 degrees with changes in said encoded signal; filtering means coupled to said output of said balanced modulator to provide a narrow bandwidth less than 1/2 the maximum bandwidth of said sideband signal and by which said carrier frequency and low frequencies are prevented from propagating to reject all sideband frequency components which are lower than 1/4 the bit rate and which are higher than 1/2 the bit rate of said encoded signal to provide at an output a narrow sideband signal for transmission characterized in that transitions between binary levels in said encoded signal are manifested by distinct phase changes in said single sideband signal, said filtering means operative to minimize phase distortion within the sideband signal, while passing only a part of one of said sidebands. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In a high speed data transmission system for transmitting a binary NRZ data signal over a communications path, said signal transmitted as a narrow single sideband signal characterized in that there are distinct phase angle changes in said signal indicative of binary data transitions as from a zero to a one or a one to a zero, said sideband signal as transmitted being completely devoid of a carrier frequency and having only a portion of a sideband containing NRZ information in combination therewith, decoding means for such a single sideband signal, comprising:
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a limiter having an input adapted to receive said single sideband signal for providing at an output a limited version of said signal; a phase change detector means having an input coupled to said output of said limiter and having a voltage controlled oscillator tuned to the approximate center frequency of said sideband signal for providing a signal consisting of pulses at the output indicative of said distinct phase angle changes, and decoding means coupled to the output of said phase change detector means for restoring a binary NRZ data signal from said pulses.
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17. A method of encoding a binary NRZ data signal at a given clock rate to a binary data output signal of a lesser bandwidth comprising the steps of:
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(a) detecting when a bit of said NRZ signal is at a given binary state; (b) determining whether said bit at said state is to be repeated; (c) providing a crossover in said data output signal 4/4 bit periods later after first detecting said bit if said bit is to be repeated; (d) detecting a change of said state in said NRZ signal; (e) providing a crossover in said data output signal 5/4 bit periods later after detecting said change in state indicative of said change, (f) counting the change of state in said NRZ to determine 4 changes in state; (g) providing an indication of 4 changes indicative of a missing bit in said output signal, (h) determining the binary state of said missing bit to provide a 6/4 bit period delay in said output signal for one binary state and no delay for said other binary state, and restoring said missing bit. - View Dependent Claims (18, 19)
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Specification