Abstract:

Outdoor automatic guided vehicle (AGV) transportation and future intelligent unmanned vehicles require positioning accuracy high for the global positioning system (GPS), GPS L1/L2C dual-frequency signals can improve the location accuracy by correcting ionospheric delay.However, L2 civil moderate/civil long (CM/CL) codes are both much longer than L1 coarse/acquisition(C/A) codes. If the traditional acquisition algorithm is applied to L2C acquisition directly, it will lead to much longer acquisition time and even failed acquisition. Therefore, an algorithm is proposed, which accomplishes CM acquisition by using the acquired Doppler shift and C/A code phase of L1 signals, then similarly finishes CL acquisition by the CM aided code phase, which makes the twodimension searching process for L2C acquisition narrow down to searching one dimension code phase with fewer discrete points. Meanwhile, the split-radix fast Fourier transform (SFFT) instead of traditional radix2 FFT is introduced into correlation operation, which can reduce the calculated quantity further. Simulation results show that the suggested algorithm can achieve accurate acquisition of dual-frequency signals with much lower calculated amount.