GPS receiver using data bit timing to achieve a fast time to first fix
First Claim
1. A global positioning system (GPS) receiver for receiving a GPS satellite signal including a GPS data bit having a time-of-arrival synchronized to a GPS-based clock time, comprising:
- a correlation system for receiving a GPS signal representative of said GPS satellite signal and providing a correlation signal including information for said time-of-arrival of said GPS data bit;
a local clock for providing a time clock signal including an internal clock time;
a microprocessor system coupled to the correlation system for receiving said correlation signal and coupled to the clock for receiving said time clock signal; and
a data bit timer code for inclusion in the microprocessor system including instructions for instructing the microprocessor system for synchronizing said internal clock time to said time-of-arrival of said GPS data bit for determining said GPS-based clock time.
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Accused Products
Abstract
A GPS receiver and a method for improving time to first fix (TTFF). The GPS receiver includes an internal clock for maintaining an approximate clock time during a standby mode and a microprocessor system including a data bit timer code, a temperature compensation code, and a learned time adjustment code. When the GPS receiver enters an operational mode, the data bit timer code instructs the microprocessor system for determining a GPS-based clock time by aligning the approximate clock time according to a time-of-arrival of a GPS data bit when the approximate clock time and the GPS-based clock time are estimated to be within a correction range of ten milliseconds. The temperature compensation code and a learned time adjustment code include instructions for using a stored frequency/temperature characteristic and a learned time correction, respectively, for estimating and compensating for time drift that has occurred during the standby mode. A temperature sensor provides a temperature measurement of a reference oscillator used as a time base for the internal clock.
178 Citations
16 Claims
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1. A global positioning system (GPS) receiver for receiving a GPS satellite signal including a GPS data bit having a time-of-arrival synchronized to a GPS-based clock time, comprising:
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a correlation system for receiving a GPS signal representative of said GPS satellite signal and providing a correlation signal including information for said time-of-arrival of said GPS data bit; a local clock for providing a time clock signal including an internal clock time; a microprocessor system coupled to the correlation system for receiving said correlation signal and coupled to the clock for receiving said time clock signal; and a data bit timer code for inclusion in the microprocessor system including instructions for instructing the microprocessor system for synchronizing said internal clock time to said time-of-arrival of said GPS data bit for determining said GPS-based clock time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method in a global positioning system (GPS) receiver for receiving a GPS satellite signal having a GPS data bit having a time-of-arrival synchronized to a GPS-based clock time, comprising steps of:
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providing an internal clock time in a time clock signal from a local clock; correlating to a GPS signal representative of said GPS satellite signal for providing a correlation signal having information for said time-of-arrival of said GPS data bit; and aligning said internal clock time to GPS-based clock time by synchronizing to said time-of-arrival of said GPS data bit. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification