A study of acquisition algorithm based on circumference displacement for GPS software receiver

ZHANG Biao^{1, 2, 3}, MA Hong-jiao^{1, 2}

1. National Time Service Center, Chinese Academy of Sciences, Xi′an 710600, China;

2. Key Laboratory of Time and Frequency Primary Standards, National Time Service Center,

Chinese Academy of Sciences, Xi′an 710600, China;

3. Graduate University of Chinese Academy of Sciences, Beijing 100039, China

Abstract: In allusion to the large amount of calculation in the traditional FFT acquisition algorithm, the repeated operations of FFT and carrier wipe-off in each carrier Doppler searching bin are replaced by the operation of circumference displacement for the spectrum sequence of the input signal based on the principle that the carrier wipe-off operation in time domain is equal to the circumference displacement operation in frequency-domain, thus the FFT of the input signal is implemented only once during the 2-dimension searching of carrier Doppler unit and code-phase. This algorithm does not reduce the relative energy, therefore it does not influence the acquisition probability. The experiment shows that the algorithm costs less time in acquisition and is easy to realize in hardware, and the algorithm fits the engineering of GPS software receiver.

Key words: acquisition; GPS; circumference displacement