CONTINUOUS TIME CHAOS DITHERING

• US 20130128930A1
• Filed: 01/09/2013
• Published: 05/23/2013
• Est. Priority Date: 06/08/2009
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Chester, David B., Michaels, Alan J.
• Granted Patent: US 8,542,716 B2
• Time in Patent Office: Days
• US Class Current: 375/152
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/0018 Chaotic
• CPC Class Codes: H04J 13/102 Combining codes

Abstract

Embodiments of the present invention provide a system and method for further reducing cyclostationarity and correspondingly energy density in a chaotic spread spectrum data communication channel, 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 spread spectrum signal having a uniform sampling interval. The digital IF spread spectrum signal is converted to a sampled analog IF spread spectrum signal at a conversion rate substantially equal to the 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 analog IF spread spectrum signal. After introducing the known dither, the analog IF spread spectrum signal is upconverted to an analog RF spread spectrum signal. The first pseudo-random sequences may be designed to be a chaotic sequence.

Claims

1. A receiver apparatus for receiving an RF spread spectrum 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:

a down-converter configured for converting said RF spread spectrum signal to a received analog IF spread spectrum signal;

a dither removal circuit configured for using a second pseudo-random sequence to remove said known dither in said received analog IF spread spectrum signal and thereby generate a uniform received sampled analog IF spread spectrum signal having a uniform sampling interval; and

an analog to digital converter configured for converting said received analog IF spread spectrum signal to a received digital IF spread spectrum signal.

2. The receiver apparatus according to claim 1, wherein said second pseudo-random sequence is a chaotic sequence.

3. The receiver apparatus according to claim 1, further comprising a demodulator configured for using a de-spreading code to de-spread said RF spread spectrum signal.

4. The receiver apparatus according to claim 3, wherein said de-spreading code is a chaotic sequence.