Patent ID: 7884761

Claim:
A method for tracking a satellite signal by a global positioning system (GPS), comprising: continuously receiving a plurality of data from one of a plurality of satellites, comprising: Step 1 : retrieving a phase difference of each of the plurality of data; Step 2 : calculating an average phase difference of the plurality of calculated phase differences; Step 3 : calculating a frequency difference by using the calculated average phase difference and a frequency constant; and Step 4 : calculating a new tracking frequency by using the calculated frequency difference and a tracking frequency of a last data among the plurality of received data; receiving a subsequent plurality of data from the satellite at the new tracking frequency, and interpreting a plurality of phase inversion points of the plurality of received data; calculating a time difference between each two adjacent phase inversion points among the plurality of phase inversion points; determining whether each time difference is an integral multiple of 20 ms; and retrieving 1-bit data for every 20 ms from the plurality of data by taking a first phase inversion point among the plurality of interpreted phase inversion points as a starting point, when each time difference is an integral multiple of 20 ms.