GNSS signal multi-frequency carrier phase asynchronous joint tracking

Abstract

Many studies have been done and proved that jointly tracking GNSS multi-frequency signals transmitted from the same satellite can improve the sensitivity and robustness of signal tracking. However, current work has not elucidated the mechanism of joint tracking loop operation by in-depth quantitative theoretical analysis. Thus a synchronous-input asynchronous-update processing method for multi-frequency carrier phase joint tracking is proposed, which is applicable to contemporary mainstream GNSS receivers adopting an asynchronous signal correlation reception structure. In this paper, a linearized mathematical model of the joint tracking loop is built, a thermal noise jitter calculation equation for the joint tracking loop is derived, the dynamic stress response characteristics of the joint tracking loop are examined, and the loop design requirements for eliminating the influence of inter-frequency frequency bias are clarified. Monte Carlo simulations and preliminary field tests validate the theoretical results using the B1C and B2a pilot signals of the MEO satellite in the BeiDou satellite navigation system (BDS). Experimental results show that the carrier phase tracking threshold of the B1C and B2b signals can be reduced by about 1 dB and 3.5 dB, respectively.