Discrete time chaos dithering
First Claim
1. A method for reducing cyclostationary content in a chaotic spread spectrum data communication channel, comprising:
- digitally generating a first transmit-side chaotic sequence of values to form a spreading code;
using said spreading code to form a digital intermediate frequency (IF) spread spectrum signal having a uniform sampling interval;
selectively varying a duration of said sampling interval in accordance with a first pseudo-random sequence to introduce a known dither in said digital IF spread spectrum signal;
subsequent to introducing said known dither, converting said digital IF spread spectrum signal to an analog RF spread spectrum signal at a conversion rate that exceeds said sampling interval.
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Abstract
The invention concerns a chaotic communications system, method and apparatus having a transmitter configured to spread an input data signal over a wide intermediate frequency band, by digitally generating a first chaotic sequence of values to form a spreading code. The spreading code is then used to form a digital IF chaotic spread spectrum signal having a uniform sampling interval. The duration of the sampling interval is then selectively varied in accordance with a first pseudo-random sequence, thereby introducing a known dither in the digital IF chaotic spread spectrum signal. After introducing the known dither, the digital IF chaotic spread spectrum signal is converted to an analog RF spread spectrum signal at a conversion rate that exceeds the sampling interval of the chaotic spread spectrum signal. A corresponding receiver recovers the input data from the spread transmitted signal. This spreading may utilize a chaotic sequence employing discrete time chaos dithering.
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Citations
19 Claims
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1. A method for reducing cyclostationary content in a chaotic spread spectrum data communication channel, comprising:
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digitally generating a first transmit-side chaotic sequence of values to form a spreading code; using said spreading code to form a digital intermediate frequency (IF) spread spectrum signal having a uniform sampling interval; selectively varying a duration of said sampling interval in accordance with a first pseudo-random sequence to introduce a known dither in said digital IF spread spectrum signal; subsequent to introducing said known dither, converting said digital IF spread spectrum signal to an analog RF spread spectrum signal at a conversion rate that exceeds said sampling interval. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for reducing cyclostationarity in a chaotic spread spectrum data communication channel, comprising:
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a first digital generator configured for producing a first transmit-side chaotic sequence of values to form a spreading code; a modulator configured for using said spreading code to form a digital intermediate frequency (IF) spread spectrum signal having a uniform sampling interval; a timing variation apparatus configured for selectively varying a duration of said sampling interval in accordance with a first pseudo-random sequence to introduce a known dither in said digital IF spread spectrum signal; a digital-to-analog converter accepting said digital IF spread spectrum signal incorporating said known dither, and producing an analog IF spread spectrum signal at a conversion rate that exceeds said sampling interval of said digital IF spread spectrum signal. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An apparatus for reducing cyclostationarity in a chaotic spread spectrum data communication channel, comprising:
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a first digital generator configured for producing a first chaotic sequence of values to form a spreading code; a modulator configured for using said spreading code to form a digital intermediate frequency (IF) spread spectrum signal having a uniform sampling interval; a timing variation apparatus configured for selectively varying a duration of said sampling interval in accordance with a second chaotic sequence to introduce a known dither in said digital IF spread spectrum signal; a digital-to-analog converter accepting said digital IF spread spectrum signal incorporating said known dither, and producing an analog IF spread spectrum signal at a conversion rate that exceeds said sampling interval of said chaotic spread spectrum signal.
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16. A receiver, comprising:
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an antenna configured to receive an RF spread spectrum signal having a duration of sampling intervals selectively varied in accordance with a first chaotic sequence to introduce a known dither in said RF spread spectrum signal; a converter configured to convert said RF spread spectrum signal to a received digital IF spread spectrum signal; a generator configured to produce a second chaotic sequence which is identical to said first chaotic sequence; and a dither removal circuit configured to use said second chaotic sequence to remove said known dither in said received digital IF spread spectrum signal, and thereby generate a uniform received digital IF spread spectrum signal having a uniform sampling interval. - View Dependent Claims (17)
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18. A receiver for receiving an RF spread spectrum signal, the signal having a duration of sampling intervals selectively varied in accordance with a first pseudo-random sequence to introduce a known dither in said RF spread spectrum signal, comprising:
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a converter configured to convert said RF spread spectrum signal to a received digital IF spread spectrum signal; a generator configured to produce a second pseudo-random sequence which is identical to said first pseudo-random sequence; a dither removal circuit configured to use said second pseudo-random sequence to remove said known dither in said received digital IF spread spectrum signal and thereby generate a uniform received digital IF spread spectrum signal having a uniform sampling interval; a de-spreader configured to despread said digital IF spread spectrum signal using a despreading sequence; and a digital chaos generator configured to generate said de-spreading sequence.
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19. A receiver for receiving an RF spread spectrum signal, the signal having a duration of sampling intervals selectively varied in accordance with a first pseudo-random sequence to introduce a known dither in said RF spread spectrum signal, comprising:
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a converter configured to convert said RF spread spectrum signal to a received digital IF spread spectrum signal; a generator configured to produce a second pseudo-random sequence which is identical to said first pseudo-random sequence; and a dither removal circuit configured to use said second pseudo-random sequence to remove said known dither in said received digital IF spread spectrum signal and thereby generate a uniform received digital IF spread spectrum signal having a uniform sampling interval; wherein said first and second pseudo-random number sequences comprise chaotic sequences.
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Specification