Two-step compressed acquisition method for Doppler frequency and Doppler rate estimation in high-dynamic and weak signal environments

To acquire global navigation satellite system (GNSS) signals means four-dimension acquisition of bit transition, Doppler frequency, Doppler rate, and code phase in high-dynamic and weak signal environments, which needs a high computational cost. To reduce the computations, this paper proposes a two-step compressed acquisition method (TCAM) for the post-correlation signal parameters estimation. Compared with the fast Fourier transform (FFT) based methods, TCAM uses fewer frequency search points. In this way, the proposed method reduces complex multiplications, and uses real multiplications instead of improving the accuracy of the Doppler frequency and the Doppler rate. Furthermore, the differential process between two adjacent milliseconds is used for avoiding the impact of bit transition and the Doppler frequency on the integration peak. The results demonstrate that due to the reduction of complex multiplications, the computational cost of TCAM is lower than that of the FFT based method under the same signal to noise ratio (SNR).