Title:
CALIBRATED REAL TIME CLOCK FOR ACQUISITION OF GPS SIGNALS DURING LOW POWER OPERATION
Document Type and Number:
WIPO Patent Application WO2003038464
Kind Code:
A3
Abstract:
Power is conserved in a Global Positioning System (GPS) receiver (100) by shutting down selected components during periods when the GPS receiver (100) is not actively calculating the GPS receiver location. A low power time keeping circuit (200) accurately preserves GPS time when the selected components are deactivated. When the selected components are turned on in response to a wake-up command, time provided from the low power time keeping circuit (200), corrected for actual operating temperatures, and data from the GPS clock temperature/frequency table (224), are used to recalibrate time from a GPS oscillator (204). Positions of the GPS satellites are then estimated such that the GPS time is quickly determined from the detected satellite signals. Once real GPS time is determined from the detected satellite signals, the selected components are deactivated. The process described above is repeated such that accurate GPS time is maintained by the low power time keeping circuit (200).
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Inventors:
GRONEMEYER STEVEN A
Application Number:
PCT/US2002/034740
Publication Date:
November 20, 2003
Filing Date:
October 30, 2002
Export Citation:
Assignee:
SIRF TECH INC (US)
International Classes:
G01S1/00; G01S19/23; G01S19/34; G04C10/04; G04F5/00; G04G19/12; G06F1/14; G06F1/32; (IPC1-7): G01S3/16; G01S5/02; H04B7/185; G06F19/00
Foreign References:
| US5893044A | 1999-04-06 | |||
| US5940027A | 1999-08-17 | |||
| US5864315A | 1999-01-26 | |||
| US5654718A | 1997-08-05 | |||
| US5629708A | 1997-05-13 | |||
| US5592173A | 1997-01-07 |
Other References:
See also references of EP 1451605A4
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