Abstract: This paper has deduced dynamic equations of the code loop of the GPS receiver which operates in coherent and noncnherent' manner when C/A code signal is considered. The contradictory requirements imposed on the code loop bandwidth by the noise response and manoeuvre tracking are analysed in detail as well. It is proposed that the contradiction can be solved by the velocity aiding from the inertial navigation system. The results show that if a narrow bandwidth code loop is aided by the inertial navigation system of 1nm/h accuracy, the manoeuvre tracking error will be 1/1000 as large 3.s that of without aiding, and thus both high anti-jamming and manoeuvre tracking performances can be achieved.

Key words: inertial navigation, satellite navigation, phase-locked loop, signal-to-noise ratio, tracking, error.