GPS L2C ACQUISITION AND TRACKING

Author

Arjun Shekar Sadahalli, Southern Illinois University CarbondaleFollow

Date of Award

1-1-2009

Degree Name

Master of Science

Department

Electrical and Computer Engineering

First Advisor

Pourboghrat, Farzad

Abstract

Global Positioning Systems (GPS) is undergoing stunning changes and upgrades which will enhance the Civil and Military users. This modernization included new satellite signals for Civil and Military purposes which benefits the fundamental signal acquisition and tracking of the GPS receiver. These new signals enable a new family of alternatives for mitigating the ionospheric errors that currently limit the GPS accuracy [16]. A new Civil signal L2 Civil (L2C) was commissioned on the L2 frequency which could have ionospheric error elimination capability, with better cross correlation, Data recovery performance, and threshold tracking. The complex structure of the signal calls for new Acquisition approaches which are implementable with limited computational burden. This thesis proposes an Acquisition methodology to acquire the Code phase offset and Carrier frequency offset of the L2C signal which can be implemented in real time. The algorithm employs a serial code search for Code Phase by retaining the original sampling frequency `fs' and implements a FFT search for carrier frequency offset with a reduced sampling frequency of `fs/M' where `M' is the decimation rate. Multirate Filters are employed for reducing the sampling frequency. After the Acquisition is performed, the values are passed onto the Phase Lock Loop (PLL) and Delay Lock Loop (DLL) to further synchronize the Code Phase and Carrier frequency. The algorithm was tested on a real data set for the performance evaluation of Acquisition and Tracking, and the navigation bits were extracted and the results discussed.