Synchronization Issues in PRN Radars Implemented with SDR Using GNU Radio

Radars have been implemented using Software Defined Radios (SDR) for more than a decade. SDRs are convenient in terms of hardware development since the signal generation, conditioning, and post-processing can easily be implemented in hardware. However, signal synchronization remains a major issue, and it can seriously impact the final performance. In this study, the synchronization and the calibration of the transmitted signals in an SDR-based radar transmitting PRN modulated pulse is studied. Time synchronization and jitter are compensated using a "Filter Delay" block, and a peak detector in a reference channel. The amplitude and phase of the peak of the cross-correlation of a sample of the transmitted signal is used to calibrate the received echoes allowing to compensate on a pulse-by-pulse basis the amplitude and phase drifts.