Patent ID: 7532159
Filing Date: 2009-05-12
Classification: G01S

Abstract:
1. A global navigation satellite system (GNSS) receiver having a fast time to first fix, comprising: an always-on real time clock for maintaining an RTC time having increments of a certain time period; an RTC calibrator including a fraction calculator for determining a time fraction of said certain time period when the receiver has power on, and an RTC time expander for using said time fraction for calibrating said RTC time when the receiver is switched from power off to power on; and a signal navigation processor for using said calibrated RTC time for assisting a determination of said first fix; wherein: the RTC calculator further includes a drift rate calculator for determining a drift rate of the real time clock by comparisons of said RTC time to GNSS time when said GNSS receiver has power on, a power down calculator for using said RTC time for determining an elapsed power down time, and a time drift calculator using said drift rate and said power down time for calculating an RTC time drift; and said RTC time expander uses said RTC time drift with said time fraction for providing said calibrated RTC time.