A Doppler Rate Estimation-Based Frequency Hopping Carrier Tracking Algorithm in LEO Satellite-Ground Link

Frequency hopping has good anti-interference ability. However, the high-speed movement between Low Earth Orbit (LEO) satellite and ground will lead to a large Doppler frequency of the received signal carrier. With the switching of the frequency hopping frequency point, the Doppler frequency will change abruptly, which will affect the subsequent signal demodulation. To solve this problem, a carrier tracking loop algorithm based on normalized Doppler rate estimation is proposed. The loop separates the frequency hopping agility factor from the phase and persistently locks the continuous Doppler rate. When the signal is detected to have high power interference at some frequency points, the algorithm performs delay locking to shield the disturbance to the tracking loop. The simulation results and analysis show that compared with the traditional phase-locked loop, the proposed algorithm can be well applied to frequency hopping carrier tracking in large Doppler dynamic and harsh interference environment.