Design of a reconfigurable low-complexity tracking loop for Galileo signals

The increased use of digital technology in communications is resulting in more functions of contemporary radio systems that are being implemented using a software-defined-radio (SDR) approach. The growing interest towards navigation applications, the advent of the European navigation system, Galileo, and the new generation GPS, make the SDR approach an interesting perspective to develop a software reconfigurable receiver for positioning applications. Even if the present technology does not allow the total implementation of a personal communications receiver, navigation terminals demand less stringent processing and can be almost completely designed with software defined radio techniques. One of the basic functions of a navigation receiver is the signal tracking of a CDMA modulated signal-in-space (SIS) broadcast by the satellite constellation (GPS or the future European Galileo). The better the sequence alignment performed in this stage, the better are the pseudo-range measurements used for user position triangulation. The paper discusses the digital implementation of a delay-lock-loop (DLL) tailored for navigation applications where a fine synchronization is required, with the aim of keeping as small as possible the system complexity requirement for a software-defined implementation.