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 [1]. 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 to totally implement a personal communications receiver, navigation terminals demand for less stringent processing and can be almost completely designed with software defined radio techniques. One of the basic function of a navigation receiver is the signal tracking of a CDMA modulated Signal-In-Space (SIS) broadcast by the satellites constellation (GPS or the future European Galileo). Better is the sequences alignment performed in this stage, better is the pseudorange measurements used for the user position triangulation. This paper discusses the digital implementation of a delay-lock-loop (DLL) tailored for navigation application where a fine synchronization is required, with the aim of keeping as small as possible the system complexity requirement for a software-defined implementation.