RTK performance of synthetic aperture processing on top of the ULB-PLL method with real-world urban GPS/Galileo L1/L5 signals

In previous work, we developed a ultra-low-bandwidth PLL (ULB-PLL) for a dual-frequency multi-constellation (DFMC) global navigation satellite system (GNSS) receiver using Doppler aiding based on an inertial navigation system (INS) and a clock locked loop (CLL). Both aiding signals allow one to reduce the phase locked loop (PLL) and delay locked loop (DLL) bandwidth to a fraction of one hertz, thus increasing tracking stability and multipath performance. In this paper, we extend the ULB-PLL by a coherent accumulation of early, prompt, and late correlation values. This accumulation exploits the intrinsic motion of the GNSS antenna, that is, spatial diversity, to realize a synthetic aperture antenna (SAA). It maximizes the antenna gain towards the satellite, thereby minimizing the influence of multipath signals coming from other directions. The method is analyzed via the z-transform and illustrated with both simulated and real-world GPS and Galileo signals were we demonstrate an real time kinematics (RTK) processing with the obtained code and carrier pseudoranges.