High Dynamic Carrier Tracking Using Kalman Filter Aided Phase-Lock Loop

Tracking dynamics on the GPS signal is still a big challenge to the receiver designer as the operating conditions are becoming more volatile. Usually, the phase-locked loop (PLL) is used in GPS receivers to track an incoming signal and to provide accurate carrier phase measurements. However, in high dynamic situations, the conflict between improving PLL tracking performance and the ability to track the signal necessitates some compromises in PLL design. Optimizing the stand-alone system for dynamics, generally, degrades the accuracy of measurements. The advanced signal processing techniques as maximum likelihood (ML) and extended Kalman filter (EKF) can be used to track a common trajectory exhibiting high dynamics. However, the estimated values of these algorithms can not be used directly to demodulate the signals. A combination of both inertial measurement unit (IMU) and GPS is an attractive method to deal with the problem of high dynamic tracking. Unfortunately, these units of IMU are often very expensive. In this paper, a new Kalman filter aided phase-lock loop is proposed to address this issue. Doppler derived from EKF is used to aid the carrier tracking loop for improving the performance under dynamic conditions. While the cost is significantly reduced compare with the IMU method. Simulations show that the method is feasible.