Patent ID: 7924222
Filing Date: 2011-04-12
Classification: G01S

Abstract:
1. A method for obtaining a precise intermediate frequency of a global positioning system (GPS), applied in a GPS receiver having a radio frequency (RF) module, the method comprising: searching a satellite by using a designated frequency of the RF module; receiving at least one satellite signal from the satellite with a signal frequency; obtaining an ephemeris data of the satellite by using the received satellite signal; calculating a present coordinate of the GPS receiver by using the received satellite signal; calculating a first coordinate of the satellite at a first time point by using the ephemeris data; obtaining a second coordinate of the satellite at a second time point by using the ephemeris data; calculating a traveling speed of the satellite by using the first time point, the first coordinate, the second time point, and the second coordinate; calculating a projection value of the traveling speed on a position vector from the first coordinate to the present coordinate; multiplying a carrier frequency of the satellite by a ratio between the projection value and a velocity of light to obtain an influence value of the Doppler Effect; and subtracting the influence value of the Doppler Effect from the signal frequency to obtain an intermediate frequency.