In the tracking stage of a GNSS receiver,in order to enhance the tracking performance of the loop in harsh environments,a tracking loop based on adaptive strong tracking Kalman filter(ASTKF)is proposed.A system model taking account of carrier phase,code phase,carrier frequency,etc.is developed,and the phase discriminator outputs are used as the measurements to update ASTKF.The main estimates including carrier frequency and phase are fed back to both code NCO(Numerically Controlled Oscillator)and carrier NCO,and the calculation method of the fading factors based on the chi square distribution is used in ASTKF,so the robustness of the tracking loop can be improved.The semi physical simulation results show that the proposed method reduces the position error and veloc-ity error by more than 20%in contrast to the tracking loop based on Kalman filter or strong tracking Kalman filter(STKF),effectively improving the tracking and positioning performance of GNSS receiver.
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