In this paper, we come up with the idea of using frequency shift method to strip carrier when acquiring the GPS signal. The RF uses the quadrature demodulator and dual channel to sample the signal, forming the IF digital signal in I channel and Q channel. The paper derivates the mathematical formula of the frequency shift method, and compares the trigonometric function method with it from the aspect of schematic diagram and calculating. Also, we make simulation of the two schemes using Matlab for both true signal and analog signal. And it comes out that the frequency shift method has got a much greater correlation peak than the trigonometric function method. So we come to the conclusion that it is better using the frequency shift method to acquire signal in low signal intensity.
