NAVIGATION-SATELLITE RECEIVER SYSTEM, AND METHOD FOR SPEEDING UP WARM START OF HIGH-SENSITIVITY NAVIGATION-SATELLITE RECEIVER IN ENVIRONMENT WITH WEAK SIGNAL

摘要

PROBLEM TO BE SOLVED: To provide skipping of Z-counts and an accurate time in a GPS receiver. SOLUTION: The navigation-satellite receiver comprises high-sensitivity radio frequency front-end and a navigation processor associated with a client CPU. The client CPU runs an operating system that serially communicates with the navigation processor. The client CPU can also obtain navigation data system transmissions from a network server and provides such when the direct satellite signals in the high-sensitivity environment are too weak to be demodulated directly. A low power, low frequency oscillator with a watch-type crystal and counter are used as a real time clock to keep time uncertainty under fifty milliseconds when the receiver is hibernating. If the time uncertainty and position uncertainty are below certain maximums when the receiver is re-awakened, then a minimum number of satellites will be needed and making a preliminary z-count to each can be avoided. COPYRIGHT: (C)2006,JPO&NCIPI