A Complete IF Software GPS Receiver: A Tutorial about the Details

Description

ABSTRACTResearch and development continues to extend the capabilitiesand to increase the robustness of Global NavigationSatellite Systems (GNSSs) receivers. Softwarereceivers are quite valuable in evaluating potentialimprovements because of their flexibility. In addition,software receivers afford batch data processing optionsthat are not available in hardware implementations. Indeveloping such a receiver, we have found that manyexisting texts and papers on software receivers omitimportant implementation details. Here we discuss ourcomplete Intermediate Frequency (IF) software GPSreceiver and reveal details of the lessons learned during itsconstruction. Specific topics addressed in this paperinclude: linear and non-linear adaptive analog-to-digital conversion; acquisition using coherent and non-coherent integration; search techniques (e.g. , Vernier, M of N, and Tong)performed in both the time domain and the frequencydomain; limitations of the DFT approach including leakage; zero padding and additional DFT enhancements; tracking utilizing FLLs, PLLs and DLLs; bit synchronization and navigation data recovery; frame synchronization and parity decoding; calculation of the navigation solution; and, Summary of our MATLAB and C toolkitsThis paper will present examples and results we have generatedusing sampled GPS signals collected with a highspeed data recorder