A High-Precision Doppler Frequency Estimation Algorithm for CDMA-TDMA Navigation Signal Structure

In the pseudolite-based area navigation system, the code division multiple access (CDMA) and time division multiple access (TDMA) signals are usually jointly applied to solve the near-far effect. However, the effective integration time during acquisition is shortened due to the characteristic of TDMA signal, and the accuracy of Doppler frequency estimation is then reduced, which does not meet the requirement of carrier tracking loop. To solve this problem, this paper proposes a high-precision Doppler frequency estimation algorithm. In this algorithm, the low-precision estimation of Doppler frequency is obtained during acquisition. Thereafter, the medium-precision estimation is realized by non-coherent integration and quadratic interpolation. Finally, Prolonging the effective coherent integration time via data code searching, high-precision Doppler frequency estimation is obtained. Experiments are carried out with the measured data, and the results show that the accuracy of Doppler frequency estimation is greatly improved, and meets the requirement of carrier tracking loop.