Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2000-06-27
2004-05-25
Chin, Stephen (Department: 2734)
Pulse or digital communications
Spread spectrum
Direct sequence
C380S270000
Reexamination Certificate
active
06741636
ABSTRACT:
BACKGROUND
Field of the Invention
This invention is related to secure data transmission systems. In the prior art, digital data transmission systems were based on independent symbols and minimization of intersymbol interference (ISI). There is a universal use of direct sequence pseudo noise spread spectrum (DS-PN SS) techniques creating white spectral density. This approach is insufficient to create a waveform with the desired white and gaussian characteristics of noise in the natural environment. Such attributes assure the highest possible degree of privacy in communication transmissions.
Thus, it is desirable to create a communication system that achieves a higher degree of private transmissions than is presently available today.
SUMMARY OF THE INVENTION
This invention relates to secure data transmissions. Specifically, it is related to digital data communication systems that communicate digital data in a manner that makes nearly indistinguishable from noise, by giving the transmitted data white noise and gaussian characteristics. Noise-like signal generation is achieved by merging white noise characteristics of DS-PN SS techniques and a unique gaussian distribution technique in the time domain.
The basis for achieving the white noise and gaussian characteristics is the application of correlative techniques to the spread spectrum output. In the prior art, correlative techniques have been applied to high speed commercial transmissions and to magnetic disks for memory storage. The unique use of correlative techniques in this application allows for limited amounts of ISI, whereas the prior art teaches to drive the ISI to null. By effectively using correlative techniques, memory is built into the symbols, the symbols are dependent and have patterns that can be interpreted.
The system and method for converting digital data into a noise-like waveform utilizes a unique method of modulation that results in a system that makes it very hard or impossible to detect the information contained within the transmitted signal, or even detect the transmitted signal itself.
One object of the invention is to utilize spread spectrum technology in order to create output that is essentially white.
Another object of the invention is to provide additional security by randomizing the data and carrier.
A further object of the invention is to provide an output signal that combines white noise and a gaussian distribution to closely approximate actual noise; such a signal will have continuous spectrum and no discrete features.
Yet a further object of the invention is to lower the spectral density of the output signal by up to 3dB.
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Chin Stephen
Lockheed Martin Corporation
McDermott & Will & Emery
Perilla Jason M.
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