The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 20, 1992
Filed:
Mar. 14, 1991
Robert A Dell-Imagine, Orange, CA (US);
Hughes Aircraft Company, Los Angeles, CA (US);
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.