| This thesis proposes a novel architecture for ultra-tight integration of a High Sensitivity Global Positioning System (HSGPS) receiver with an Inertial Navigation System (INS), to address the issue of GPS tracking and positioning in degraded signal environments. By enhancing signal tracking loops in receivers through the use of optimal controllers/estimators and aiding from external sources such as INS, the capabilities of the GPS receiver can be enhanced to provide positioning in urban canyon and indoor environments. The proposed approach is distinct from the commonly used ultra-tightly coupled GPS/INS approaches, and includes different tracking enhancement technologies used in typical HSGPS receivers, multi-channel co-operated GPS receivers and the current ultra-tightly coupled GPS/INS methods.; The proposed method in this thesis consists of three signal tracking loop types, namely conventional sophisticated Delay Lock Loops (DLL) and Phase Lock Loops (PLL) for all individual tracking channels, external INS aiding loops and multi-channel co-operated tracking loops, namely COOP loops. The signal tracking strategy is described, with specific focus on the role of COOP loops in the proposed ultra-tightly coupled GPS/INS. Furthermore, the effect of inertial measurement unit (IMU) quality and the effect of receiver oscillator noise and coherent integration time on weak signal tracking are also analyzed.; To perform ultra-tight integration, an INS simulator is developed, and static and dynamic field tests are simulated to analyze the system performance. The test results show that the proposed INS-aided GPS receiver can track the incoming weak GPS signals down to a C/No of 15 dB-Hz without carrier phase locked, or 25 dB-Hz with carrier phase locked. When there are multiple strong GPS signals in view, the other weak signals can be tracked down to 15 dB-Hz with carrier phase locked. |
