A Coherent Processing Technique with High Precision for BDS B1I and B1C Signals

The smooth transition constraint and constant envelope restriction of the Beidou Navigation Satellite System (BDS) make the legacy regional system B1I signal and new global system B1C signal, which are located at different center frequencies, coexist in the BDS-3 B1 band. Therefore, new modulation and multiplexing techniques need to be adopted to meet these system constraints. More specifically, single-sideband complex binary offset carrier (SCBOC) modulation and constant envelope multiplexing via intermodulation construction (CEMIC) techniques are used in B1 band to construct a multicarrier constant-envelope composite navigation signal. In particular, the SCBOC modulation technique is introduced into the B1I signal to move its main energy from the global system B1 frequency to the regional system B1 frequency. However, as of now, the SCBOC modulation has only been regarded as a means to achieve the smooth update of the BDS, whose high-precision ranging potential has not been fully understood and utilized. To solve this problem, this paper proposes a high-precision coherent processing technique, which makes full use of the coherence between B1I and B1C signals. The proposed algorithm can not only exploit the ranging performance brought by high-frequency complex subcarriers without loss, but also greatly simplify the implementation complexity of the receiver. The experimental results of live BDS-3 signals verify the effectiveness and correctness of the proposed method. This paper provides a new solution for the high-precision application of the BDS B1 composite signal and has great reference value for receiver designers.