05126748 is referenced by 95 patents and cites 37 patents.

A system and method for determining the position of an airborne object, using a fixed station and a pair of earth orbit satellites whose positions are known. Separate periodic signals are transmitted from the fixed station via the first and second satellites to the object whose position is to be determined. The phase offset in periodic characteristics of the periodic signals as received from the first and second satellites is measured at the object. The phase offset corresponds to a realtive time difference in propagation of the signals traveling two different paths to the object. The object transmits via the first satellite a return signal indicative of the measured relative time difference. This return signal is activated some time in the future according to the object local time, which is slaved to receipt of the periodic signal sent through the first satellite. This future time is the start of the particular time period as decided by the fixed station's schedule. At the fixed station, an instantaneous round trip delay, determined by the time offset of the current transmission clock time relative to the receive clock time of reception of the return signal, along with the measured relative time difference sent back on the return signal, is used to calculate the distances between the first and second satellites to the object. From these distances, along with the combined altitude of the object with the distance from the surface of the earth to the center of the earth, the position of the object is calculated.

Title
Dual satellite navigation system and method
Application Number
446979
Publication Number
5126748
Application Date
May 20, 1991
Publication Date
June 30, 1992
Inventor
Klein S Gilhousen
San Diego
CA, US
Lindsay A Weaver Jr
San Diego
CA, US
Irwin M Jacobs
La Jolla
CA, US
William G Ames
Poway
CA, US
Agent
Russell B Miller
Assignee
Qualcomm Incorporated
CA, US
IPC
G01S 3/02
G01S 5/02
H04B 7/185
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