RF subsampling GNSS receiver: Potential advantages and feasibility study

The American GPS and Russian GLONASS satellite positioning systems have been operational since the 90´s. Other GNSS systems are under development like European Galileo and Chinese Compass systems. Several mass market GNSS products allow users to have their positions, speed and time, but the majority of them are limited to a single standard and do not allow positioning in no coverage areas. Hence, it is very interesting to have a single receiver that includes several positioning systems which is capable of providing precise position indoors and outdoors. This paper deals with a new GNSS receiver architecture for GPS, GLONASS and Galileo radio signals characterized by low power and high sensitivity, also capable of providing outdoor to indoor positioning service. The proposed architecture is based on an RF subsampling down-conversion topology. A fixed subsampling frequency is chosen to properly down-convert the three constellations RF bands to a fixed IF band, which relaxes the IF filter design. A Direct Digital Converter is then proposed to perform quadrature down-conversion to baseband. Simulation results show high gain and low noise for the designed RF front-end and validate subsampling frequency choice through multiband GNSS receiver condition.