Single sideband suppressed carrier digital communications method and system
First Claim
1. A method of modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said method comprising the steps of:
- identifying select ones of said input data bits which repeat the data state of a respectively preceding one of said input data bits;
identifying select ones of said pulses which correspond to said select bits; and
, alternately shortening and lengthening said periods associated with said select ones of said pulses.
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Abstract
A method of modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing. The method includes the steps of: identifying select ones of the input data bits which repeat the data state of a respectively preceding one of the input data bits; identifying select ones of the pulses which correspond to the select bits; and, alternately shortening and lengthening the periods associated with the select ones of the pulses.
129 Citations
34 Claims
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1. A method of modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said method comprising the steps of:
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identifying select ones of said input data bits which repeat the data state of a respectively preceding one of said input data bits;
identifying select ones of said pulses which correspond to said select bits; and
,alternately shortening and lengthening said periods associated with said select ones of said pulses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
selecting a first and a second number of said apertures;
reversing a phase associated with each select pulse after said first number of apertures in a first mode; and
,reversing said phase associated with each select pulse after said second number of apertures in a second mode.
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4. The method of claim 1, wherein said alternately shortening and lengthening said period further comprises, alternating between said first and second modes each time it a select bit is identified.
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5. The method of claim 4, further comprising:
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selecting a third number of said plurality of apertures;
reversing said phase of each other of said pulses after said third number of apertures in a third mode.
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6. The method of claim 5, wherein each said preceding bit immediately precedes one of said select bits, respectively.
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7. The method of claim 5, wherein:
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said third number is greater than said first number; and
,said second number is greater than said third number.
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8. The method of claim 7, wherein said third number of apertures corresponds to said associated temporal duration.
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9. The method of claim 1, wherein positive and negative excursions for each of said pulses are one bit width wide, plus or minus a small fraction of said bit width so as to keep the bit widths continuously changing plus or minus by equal amounts during long periods of transmitted marks or spaces.
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10. The method of claim 1, wherein a start of a string of ones or zeros as said input bits is indicated by a shortened or lengthened pulse width, followed immediately by a width change in an opposite direction.
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11. The method of claim 1, wherein a frequency spectrum resulting from said modulation is a substantially single frequency line at ½
- the bit rate without visible frequency or phase modulation, but which is detectable from bipolar phase reversals.
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12. The method of claim 11, further comprising:
- doubling the single frequency spectral line to yield a data clock signal.
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13. The method of claim 1, further comprising introducing strings of ones or zeros to reset the clock repeatedly on only one time boundary edge, to prevent a shift in clock timing.
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14. The method of claim 1, further comprising:
- filtering off Fourier products without loss of phase change magnitude.
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15. The method of claim 1, further comprising single sideband suppressed carrier modulating a carrier signal to produce a single spectral frequency alternating in phase at a desired frequency.
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16. The method of claim 15, wherein the encoded single sideband frequency is added to analog TV signals on a cable distribution system to add digital channels between analog channels without substantially interfering with the analog channels.
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17. A modulator for modulating a bipolar signal including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said modulator comprising:
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means for identifying select ones of said input data bits which repeat the data state of a respectively preceding one of said input data bits;
means for identifying select ones of said pulses which correspond to said select bits; and
,means for shortening and lengthening said periods associated with said select ones of said pulses.
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18. A filter suitable for use in modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said filter comprising:
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a transformer including first and second secondary nodes;
a first capacitor coupled to said first node;
a crystal oscillator coupled to said second node; and
,a second capacitor coupled to said second node;
wherein, when the crystal oscillator is excited by a narrow band rapidly phase reversing signal frequency acts as a reference element only.
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19. A filter suitable for use in modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said filter comprising:
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a reference resonator having a group delay; and
,a signal path that bypasses the resonator, such that the group delay of the resonator does not factor in transmission of said modulated pulses, but determines a bandwidth of the filter by virtue of said resonator being used as an impedance reference only. - View Dependent Claims (20, 21, 22)
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23. A method of digital data encoding a multiplicity of data bits, each having a data state, to cause a phase or polarity reversal each bit period while changing the temporal duration of each bit period to encode the data, the said method comprising the steps of:
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identifying the data state of the last incoming bit;
alternately shortening and lengthening duration of the phase reversal period if the bit is repeated;
reversing phase or polarity at exactly one bit period if the data state changes from a one to a zero or vice versa. - View Dependent Claims (24, 25, 26, 27, 28)
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29. A filter suitable for use in modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said filter comprising:
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a reference resonator having a group delay independent of a group delay of the filter operated in a parallel mode having a high impedance at a frequency associated with said temporal duration such that said pulses do not pass through it, and provides negative feedback at frequencies off resonance; and
,a signal path that bypasses the resonator, such that the group delay of the resonator does not factor in transmission of said modulated pulses, but determines a bandwidth of the filter by virtue of said resonator being used as an impedance reference only.
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30. A filter suitable for use in modulating a phase reversing pulse train including a plurality of signal pulses each having an associated period of a given temporal duration to encode a multiplicity of input data bits each having a data state, and prevent losses of clock timing, said filter comprising:
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a reference resonator having a group delay having a group delay independent of a group delay of the filter operated in a series mode, providing positive feedback that accentuates the gain of the filter at a resonant frequency, and is not in a signal of said modulated pulses; and
a signal path that bypasses the resonator, such that the group delay of the resonator does not factor in transmission of said modulated pulses, but determines a bandwidth of the filter by virtue of said resonator being used as an impedance reference only.
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31. A digital communication system comprising:
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a means for modulating a pulse train wherein a Fourier frequency components bearing abrupt changes of phase, each of said Fourier frequency components being a single frequency; and
a filtering means operable to pass a selected one of said Fourier frequency components. - View Dependent Claims (32, 33, 34)
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Specification