Gps receiver having a rapid acquisition of gps satellite signals

Abstract

A GPS receiver having a rapid acquisition of a GPS satellite signal when a normal operational mode is entered after a low power standby mode. The GPS receiver includes an RF section for receiving the GPS satellite signal and providing an GPS IF signal, a correlator section for providing a correlation signal for the correlation between the GPS IF signal and a GPS replica signal, and a microprocessor section for receiving the correlation signal and calculating a geographical location of the GPS receiver. The GPS replica signal is based upon a reference frequency from a reference oscillator and a reference time from a timer. In the standby mode, the operation of the RF section, correlator section, and microprocessor section is inhibited while the reference oscillator and time continue to operate. In order to increase acquisition speed upon entering the normal mode, the microprocessor section provides the correlator section with an initial frequency adjustment to correct for drift in the reference frequency during the standby mode. The microprocessor section provides the initial frequency adjustment based upon a learned frequency correction that is based upon the frequency adjustment that results in acquisition of the GPS satellite signal after alternating one or more times between the standby mode and the normal mode. Alternately, the initial frequency adjustment is calculated from a stored frequency/temperature relationship and a temperature for the reference oscillator measured by a temperature sensor.