Hybrid GPS/Galileo/GLONASS IF Software Signal Generator

A Global Navigation Satellite System (GNSS) signal simulator is a necessity for the development and validation phases of a GNSS receiver. By connecting the 1233 ION GNSS 18th International Technical Meeting of the Satellite Division, 13-16 September 2005, Long Beach, CA simulator to the antenna port of a receiver, the latter can navigate as if it is on a real vehicle. Indeed, there are many other advantages for using such a simulator. For example, the same simulation scenarios can be run repeatedly until the desired outcomes are achieved. Also, the simulator would allow testing GNSS receivers in various environments and characterizing the receiver's behavior in unusual or unexpected conditions. The efficiency of the receiver’s development is ensured by working in a controlled and repeatable test environment. A hybrid GNSS receiver requires the GPS, Galileo and/or GLONASS signals as input. Hence, the design process of hybrid receivers requires a hybrid signal simulator that can generate the GPS, Galileo and/or GLONASS signals. Specifically, the hybrid signal simulator should generate the following signals: GPS L1 and L5, Galileo E5a, E5b and E6, GLONASS L1 and L2 signals. However, the cost of such a simulator is very high and not all functionalities are available. The need for low-cost reprogrammable signal generators is becoming urgent in several fields (e.g. geomatics engineering) and a low-cost software defined hybrid signal simulator would be an enormous asset for the development of hybrid receivers. As the Galileo satellite constellation and signal generation are still in the development phase, GPS will be modernized and GLONASS updated, the GNSS signal simulator should be very flexible and should give the possibility for easy updates and changes in order to be as much realistic as possible. This paper presents a software IF signal generator called IF Software Defined Signal Simulator (SDSS), which has been developed in Matlab/Simulink and the platform is under implementation and test in FPGA (Field Programmable Gate Array). The simulator allows the user to control many parameters, such as the choice of the disturbance and propagation channel parameters, various pre-defined environments, etc.