GPS satellite signal tracking system for GPS receivers

摘要

A satellite signal tracking system for a GPS receiver, wherein a GPS satellite is recaptured within a very short period of time, after the interruption of reception is cleared as by passing through a tunnel and the like, by widening a band width of the PLL search frequency gradually every after repeating the search for the satellite signal, performing a narrow-band search repeatedly as varying its center frequency along the Doppler shift curve, performing a narrow-band search for a specific period of time which is given by dividing the capture range of the PLL circuit by the Doppler shift rate and a wide-band search with use of an estimated satellite signal receiving frequency which is given by recalculating the Doppler frequency of the GPS satellite at the very moment according to the almanac data of the GPS satellite and is assigned as the center frequency, and, still further, performing the search for GPS satellites repeatedly with the estimated satellite signal receiving frequency in the center for recovering the function to perform the positional reckoning which is the primary function of the GPS receiver.