EP0635728A1
Expired / Lapsed
EP
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Satellite search methods for improving time to first fix in a GPS receiver
Assignee: Trimble Inc
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Filing: 1994-07-07
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Granted: —
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Expires: 2014-07-07
Abstract
Abstract An embodiment of the present invention includes a GPS receiver capable of concurrently tracking up to eight GPS satellites. The GPS receiver comprises computer-implemented methods for parallel search, split search and precomputation. The parallel search method causes the apparent Doppler frequency spectrum to be sectioned into several segments and a first GPS satellite signal is searched for in parallel in each of the segments. When the first GPS fix is not found after a predetermined time has expired, a split search is begun.
Inventors
- 👤 Paul W. Mcburney
- 👤 Lynn Weber
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 19:05
CPC Classifications
G; G01; G01S; G01S19/00; G01S19/01; G01S19/13; G01S19/23; G01S19/235; G01S19/24; G01S19/28; G01S19/29
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
197 words
A method for searching for acquisition of a signal from a GPS satellite with a multiple channel GPS receiver, the method comprising the steps of: pre-computing a table of pseudo random number (PRN) codes associated with GPS satellites predicted to be visible at a plurality of times in the future based on a current time and GPS satellite almanac and a predetermined geographic position; fetching a PRN code from said table according to a time said GPS receiver is re-powered up after a period of non-operation that followed the step of pre-computing said table; searching for a signal from a first GPS satellite associated with said fetched PRN code in parallel using said multiple channels of said GPS receiver such that a first search range is positioned with a nominal frequency for said GPS satellite signal at its mid-point and a first channel is appointed to search said first search range and a second channel is appointed to search in parallel a second search range adjacent to said first search range; and splitting said multiple channels between searching for said first GPS satellite and a second GPS satellite if said first GPS satellite signal was not found.
Claim 2
Dependent Claim
38 words
The method of claim 1, wherein: the pre-computing of said table includes ephemeris information obtained previous to said period of non-operation and said table extends forward in time for period limited by the validity of said ephemeris information.
Claim 3
Independent Claim
97 words
A method for searching for acquisition of a signal from a predetermined candidate GPS satellite with a multiple channel GPS receiver, the method comprising the steps of: pre-computing a table of pseudo random number (PRN) codes associated with GPS satellites predicted to be visible at a plurality of times in the future based on a current time and GPS satellite almanac and a predetermined geographic position; and fetching a PRN code from said table according to a time said GPS receiver is re-powered up after a period of non-operation that followed the step of pre-computing said table.
Claim 4
Independent Claim
236 words
A method for searching in parallel for acquisition of a signal from a GPS satellite with a multiple channel GPS receiver, the method comprising the steps of: pre-selecting a particular carrier frequency as a nominal frequency within an apparent Doppler frequency spectrum for GPS satellite signals; partitioning said apparent Doppler frequency spectrum into a plurality of adjacent search ranges such that a particular first search range near the center of said apparent Doppler frequency spectrum includes said nominal frequency; appointing a first of said GPS receiver channels to search said first search range; appointing a second of said GPS receiver channels to search a second search range above and adjacent to said first search range; appointing any but said first of said GPS receiver channels to search a third search range below and adjacent to said first search range; searching within said first and at least one of said adjacent search ranges for said signal from a GPS satellite and terminating the search if said signal is found; appointing any but said first of said GPS receiver channels to search a fourth search range above and adjacent to said second search range; appointing any but said first of said GPS receiver channels to search a fifth search range below and adjacent to said third search range; searching within said first and at least one of said adjacent search ranges for said signal from a GPS satellite.
Claim 5
Dependent Claim
196 words
A multiple channel GPS receiver, comprising: GPS navigational computer means for pre-computing a table of pseudo random number (PRN) codes associated with GPS satellites predicted to be visible at a plurality of times in the future based on a current time and GPS satellite almanac and a predetermined geographic position; table indexing means for fetching a PRN code from said table according to a time said GPS receiver is re-powered up after a period of non-operation that followed the step of pre-computing said table; radio receiver means for searching for a signal from a first GPS satellite associated with said fetched PRN code in parallel using said multiple channels of said GPS receiver such that a first search range is positioned with a nominal frequency for said GPS satellite signal at its mid-point and a first channel is appointed to search said first search range and a second channel is appointed to search in parallel a second search range adjacent to said first search range; and multi-channel GPS receiver means for splitting said multiple channels between searching for said first GPS satellite and a second GPS satellite if said first GPS satellite signal was not found.
References Cited (Backward Citations)
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