A USRP-based GNSS and interference signal generator and playback system

This paper presents a low cost, portable, and flexible GNSS signal and interference signal generator based on a general purpose software radio front end, the Universal Serial Radio Peripheral (USRP) family of devices. We paired a USRP-N210 mother board with appropriate RFX daughter boards to generate all GNSS signals controlled by a personal computer. The source of the signal can be pre-recorded digital samples obtained from specific RF front end or arbitrary samples generated using MATLAB programs. An adjustable low noise signal amplifier mounted between the USRP output and the transmitting antenna was used to control the transmitted power of the signal. A spectrum analyzer was used to directly monitor the transmitted signal. The NovAtel receiver was used to verify the performance of this signal generator and playback system. The received GNSS data after transmitting via USRP-N210 and the original GNSS data before transmitting are processed by NovAtel receiver and software receiver programs respectively for performance evaluation purposes. Some comparisons had been done to demonstrate the accuracy of the playback system.