Algorithm Research on High-Precision Tracking of Beidou-3 B1C Signal

Abstract

The B1C signal of Beidou-3 satellite navigation system adopts data and pilot separation to realize the transmission of message information and ranging functions. The traditional tracking method uses separate data to demodulate the message information, which doesn’t fully utilize the signal energy and data-pilot phase relationship, resulting in low tracking accuracy. In order to demodulate the navigation message information more accurately, based on the phase relationship between the data channel and the pilot channel, this paper introduces the tracking strategy of “data + pilot” joints in loop tracking, and proposes three joint methods with different complexity, including “correlator output amplitude superposition”, “discriminator output linear union” and “loop filter output linear union”. The tracking accuracy of pseudo-code tracking loop and carrier tracking loop under different joint modes is theoretically analyzed, and the applicability of joint tracking in different scenarios is given. Finally, the measured data based on different satellites shows that the higher the inter-code consistency between the data and the pilot, the more obvious the improvement of joint tracking is. The ‘correlator output amplitude superposition’ method performs the high tracking accuracy and the simplest structure under higher SNR conditions. Under lower SNR conditions, the combination of “code loop filter output linear union + carrier loop discriminator output linear union” shows the highest tracking accuracy and the lowest tracking threshold. Although the loop filter combination increases the loop complexity, it adapts to a wider scene.