Design of Optimal Baseband Processor for Modernised GPS Signals

The acquisition and tracking of the GPS signals are the important and most challenging function in modernised GNSS receivers. In this paper this is addressed for the modernized GPS L2C signal. As an important pre-requisite, the characteristics of the modernised GPS L2C signals are presented. The correlation performance of the L2C codes is discussed. The generation of local GPS signal (the L2C code) required for the correlation during the acquisition as well as tracking is presented. Selection of some of the important variable parameters which contribute to the acquisition loop performance during acquisition is carried out. Various methods of the acquisition of the GPS L2C signals based on the linear correlation in time domain and the circular correlation in frequency domain are presented The tracking of the modernised GPS L2C signal based on the Costas PLL and the Delay Locked Loop (DLL) are presented. The acquisition and tracking of the GPS L2C signal with the assistance from the L1 C/A code signal acquisition is also presented.