Robert E Pierson

US Patent:

6476758, Nov 5, 2002

Filed:

Mar 6, 2001

Appl. No.:

09/799890

Inventors:

Christopher Chaput - Palo Alto CA
Kenneth Ehlers - Mountain View CA
Robert Pierson - Sunnyvale CA
David Rowe - San Jose CA
Jackson Ma - San Francisco CA

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

G01S 1308

US Classification:

342118, 342125, 342135, 342137, 342145

Abstract:

Systems and methods that may be used to determine the distance between an orbiting satellite and a ground station. A master clock divider circuit generates clock signals derived from a master clock. A transmit code generation circuit generates pseudo-random number codes and processes the pseudo-random number codes to produce a composite signal having positive and negative correlation peaks that is transmitted to the satellite as an analog signal. A digitizing circuit receives the analog signal transmitted from the satellite, and digitizes the analog signal. A frequency domain matched filter match filters the digitized analog signal to produce correlation peaks contained in the digitized analog signal. A central processing unit comprises a middle code software matched filter that generates an outer code bit, and computes the distance from the ground station to the satellite by calculating the difference between the time that the composite signal was received compared to the time that the composite signal was transmitted and dividing the difference value by the speed of light, and comprises an outer code software matched filter that produces a bit error rate signal indicative of the validity of the computed range value.