Gps receiver using data bit timing to achieve a fast time to first fix

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.