Pulse or digital communications – Repeaters – Testing
Patent
1991-03-14
1992-10-20
Tarcza, Thomas H.
Pulse or digital communications
Repeaters
Testing
H04L 900
Patent
active
051576880
ABSTRACT:
A spread spectrum transmitter uses simultaneous pseudorandom shifts of the transmitted carrier phase and receive local oscillator phases by 90 or 45 degrees and/or pseudorandom time shifts of the transmitted and receiver chip timing by half a chip duration to limit the coherent integration of carrier and chip rate detectors at an intercept receiver attempting to detect the transmissions. Direct sequence spread spectrum signals are intercepted and identified using an intercept receiver by recovering a spectral line corresponding to their carrier frequency or to their direct pseudo-noise chip rate. The conventional use of a phase shift with a fixed carrier frequency and/or a chip time shift with a fixed chip rate simplifies the design of the intercept receiver because the receiver is optimized to a single carrier frequency and chip rate. However, in accordance with the present invention, changing the frequency of the carrier and the chip rate demands complex changes in the intercept receiver design to implement carrier line recovery and chip linear recovery. This strategy accomplishes the desired reduction in the efficiency of the intercept receiver, and hence provides for low probability of detection.
REFERENCES:
patent: 5029180 (1991-07-01), Cowart
patent: 5029181 (1991-07-01), Endo et al.
Cain David
Denson-Low W. K.
Hughes Aircraft Company
Tarcza Thomas H.
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