Abstract:  High dynamic and weak signal carrier tracking methods in deep space communication was analyzed. The nonlinear selection problem of state equation and measurement equation in carrier tracking was proposed. The determinants in high dynamic weak signal tracking were discussed and two inferences were given. Based on Kalman filter, phaselocked loop (FLL) and unscented Kalman filter(UKF) were used to assist in different environments. Aiming at the frequency step problem in the combination tracking loop state transition,  the mathematical expression of the working mode and switching threshold of the novel loop were presented. Calculation discriminator in the loop controls the loop output and at the same time eliminates the wild value. The simulation shows that the loop algorithm has good low signaltonoise and highdynamic adaptability compared with the existing algorithms.

Key words: carrier tracking, nonlinear filtering, unscented Kalman filter(UKF), strong tracking filter, switching, wild value rejection