Improving GPS Receiver Tracking Performance of PLL by MEMS IMU Aiding

Y. Yang, N. El-Sheimy

Abstract:	The GPS signal tracking commences after the acquisition. The signal tracking generates the incoming satellite signals locally so as to estimate the carrier phase and code delay. The phase lock loop (PLL) is used in receivers to track an incoming signal phase and frequency and to provide accurate carrier phase measurement. Conventional unaided PLL implementations suffer from the noise-dynamics tradeoff. A large PLL bandwidth that is required to track dynamics increases the thermal noise. Although setting a small bandwidth for the loop filter improves noise immunity, at the expense of dynamics tracking, it increases the chance for loss of lock in highdynamics scenarios. By virtue of its immunity to RF interference and its high accuracy measurement over short time, inertial measurement unit (IMU) aiding can remove most of the GPS receiver’s dynamics of PLL. However, due to the noisy measurements and poor stability, current low-cost micro electro mechanical system (MEMS) based IMU does not meet the accuracy requirement of the direct IMU-aided PLL. This paper focuses on the implementation and performance analysis of a PLL aided by a MEMS IMU. The paper will firstly give a brief overview of the basic operation of PLL and discuss the less-than-perfect performance of IMU velocity aiding. This work is done based on NordNavr software receiver and low-cost (<$100) ADI MEMS IMU, an INS Simulator and an extended Kalman filter (EKF) with 23 states (both developed by MMSS research group, UofC).
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	2192 - 2201
Cite this article:	Yang, Y., El-Sheimy, N., "Improving GPS Receiver Tracking Performance of PLL by MEMS IMU Aiding," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 2192-2201.
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