A Digital GPS/GLONASS Signal Emulator for SDR GNSS Receivers

In this work a signal emulator of the American and Russian Global Positioning Systems is presented. The design can be used with the digital stages of the Global Navigation Satellite Systems (GNSS) receivers emulating digitally the received signals of the satellites. This is especially useful in the development and debugging stages of the receivers since it allows to test the functionality of digital processing stage (typically named correlation stage) and the software of the receivers without having a radiofrequency front-end. The signal emulator has a set of parameters to configure the frequency, phase, data bits and other variables of the output signal. The signal emulator was developed in VHDL and it was implemented in a FPGA together with a GNSS Software Defined Radio (SDR) receiver. The design was integrated as an IP-Core in a system with a LEON3 microprocessor, which works as system coordinator of the receiver, and the AMBA bus as interface communication between the LEON3, the signal emulator and other peripherals of the embedded system. The design is highly flexible and it allows to scale the implementation to multiple channels easily.