US6020847A
Expired / Lapsed
US
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Geolocation method and apparatus for satellite based telecommunications system
Assignee: Northrop Grumman Systems Corp
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Filing: 1996-04-25
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Granted: 2000-02-01
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Expires: 2016-04-25
Abstract
Abstract A method for determining the geolocation of a user terminal within a telecommunications system having a constellation of satellites which relay communications signals between earth stations and user terminals over preassigned channels. The method performs synchronization upon the telecommunications signals to calculate timing and frequency update information for the user terminals. The timing and frequency update information is also used within the earth station to calculate the geoposition of the user terminal. To do so, the earth station calculates a distance between the satellite and a user terminal based on the corresponding propagation time therebetween which is obtained from the timing information. Once the satellite to user terminal distance is obtained, a range solution line may be calculated therefrom. In addition, the frequency update information is used to calculate a Doppler solution line upon which the user terminal is positioned. Thereafter, the range and Doppler solution lines are combined to obtain points of intersection therebetween. These points of intersection represent potential geolocations of the user terminal. The earth station discriminates between these intersection points in one of several manners, such as the coverage beam spot or geographic cell assigned to the user terminal. Upon obtaining a single intersection point, the longitude and latitude of this point or output is the geolocation of the user terminal.
Inventors
- 👤 Eric L. Upton
- 👤 Scott A. Stephens
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:09
CPC Classifications
G; G01; G01S; G01S19/00; G01S5/00; G01S5/02; G01S5/12; H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/185; H04B7/1853; H04B7/18545; H04B7/18547; H04B7/1855
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
202 words
A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of: receiving a telecommunications signal over an assigned channel from a user terminal at an earth station; determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said telecommunications signal; combining said timing error offset with a round trip propagation delay representing round trip propagation time of an RF signal through said user terminal, a satellite, and said earth station to obtain an updated round trip propagation delay through said user terminal, said satellite, and said earth station; removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay; determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay; determining a Doppler solution line based on said telecommunications signal; determining geographic points of intersection of said range and Doppler solution lines; and outputting one of said geographic points of intersection as a geolocation of the user terminal.
Claim 2
Independent Claim
202 words
A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of: receiving a telecommunications signal over an assigned channel from a user terminal at an earth station; determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said telecommunications signal; combining said timing error offset with a round trip propagation delay representing round trip propagation time of an RF signal through said user terminal, a satellite, and said earth station to obtain an updated round trip propagation delay through said user terminal, said satellite, and said earth station; removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay; determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay; determining a Doppler solution line based on said telecommunications signal; determining geographic points of intersection of said range and Doppler solution lines; and outputting one of said geographic points of intersection as a geolocation of the user terminal.
Claim 3
Dependent Claim
38 words
The method of claim 1, wherein said step of outputting a geolocation comprises determining a geolocation for said user terminal based on said range solution line, said Doppler solution line, and a beam spot covering said user terminal.
Claim 4
Dependent Claim
42 words
The method of claim 1, wherein said step of outputting a geolocation comprises determining a geolocation for said user terminal based on said range solution line, said Doppler solution line, and a predefined geographic cell to which said user terminal is assigned.
Claim 5
Dependent Claim
25 words
The method of claim 1, wherein said step of determining a timing error offset comprises correlating said second telecommunications signal with a reference sync signal.
Claim 6
Independent Claim
231 words
A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of: transmitting a first telecommunications signal over an assigned channel to a user terminal; receiving a second telecommunications signal over an assigned channel from said user terminal at an earth station; determining a round trip propagation delay through said user terminal, a satellite, and said earth station based on said first and second telecommunications signals; receiving a subsequent telecommunications signal over the assigned channel from said user terminal at said earth station; determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said subsequent telecommunications signal; combining said timing error offset with said round trip propagation delay to obtain an updated round trip propagation delay; removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay; determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay; determining a Doppler solution line based on said subsequent telecommunications signal; and determining geographic points of intersection of said range and Doppler solution lines; and outputting one of said geographic points of intersection as a geolocation of the user terminal.
Claim 7
Independent Claim
231 words
A method for determining a geolocation of a user terminal in a satellite based telecommunications system which passes communications signals along assigned channels between a user terminal, a satellite, and an associated earth station, said method comprising the steps of: transmitting a first telecommunications signal over an assigned channel to a user terminal; receiving a second telecommunications signal over an assigned channel from said user terminal at an earth station; determining a round trip propagation delay through said user terminal, a satellite, and said earth station based on said first and second telecommunications signals; receiving a subsequent telecommunications signal over the assigned channel from said user terminal at said earth station; determining a timing error offset representative of motion of said user terminal relative to said earth station and based on said subsequent telecommunications signal; combining said timing error offset with said round trip propagation delay to obtain an updated round trip propagation delay; removing an earth station-to-satellite round trip delay from said updated round trip propagation delay, thereby determining a satellite-to-mobile terminal round trip propagation delay; determining a range solution line based on said satellite-to-mobile terminal round trip propagation delay; determining a Doppler solution line based on said subsequent telecommunications signal; and determining geographic points of intersection of said range and Doppler solution lines; and outputting one of said geographic points of intersection as a geolocation of the user terminal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-01-31 | 2003-08-02 | 2004-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-01-31 | 2007-08-02 | 2008-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-01-31 | 2011-08-02 | 2012-02-01 | $7700.00 | Window Closed / Lapsed |