Satellite radio acquisition method of GPS receiver

摘要

PURPOSE:To enable quick repicking of a satellite by searching a satellite radio signal with a search frequency of PLL expanded to a wider band gradually in every repetition of the search when the wave of the satellite being picked up can not be received for a prescribed time or longer. CONSTITUTION:Now, it is assumed that radio signals of a prescribed satellite received so far at a reception frequency fr becomes unreceivable and this state has continued for a predetermined prescribed time. Then a GPS receiver starts an operation of repicking of the satellite from the position of the end of this time passing. In a first search, the number (n) of search steps thereof is set at a prescribed initial value and the search of the satellite wave is repeated in a prescribed number of times with a search frequency of PLL changed over first in a range around the frequency fr at the time point when the signal turns unreceivable. When the satellite signal can not be received, it is determined that the reception frequency of the satellite signal does not exist in this range, and a transfer is made to a second searching operation with the number (n) of the steps increased by a prescribed increased number of steps. In this way, the search is executed repeatedly until a prescribed limited number of steps is reached.