Time and Phase Synchronization of a Broadband Multistatic Imaging Radar Network Using Non-Cooperative Signals

High resolution multistatic imaging radar systems pose significant challenges to the employed synchronization schemes, as such radar networks need to operate coherently. Especially high resolution systems operating at a high center frequency push the required synchronization requirements into the single-digit picosecond regime. Within the project Imaging of Satellites in Space – Next Generation (IoSiS-NG), the task at hand is further challenged by the use of far baselines, where commonly seen approaches fail, as no line-of-sight (LOS) free-space propagation or wired method can be employed. In this paper, a robust synchronization method is presented that elevates well established GNSS based methods by about three orders of magnitude through the coordinated reception of non-cooperative (NC) signals at all participating nodes. Exploiting the identical signal payload at all stations, the timing and phase differences of the nodes can be tracked and corrected in the post-processing stage. Here, we demonstrate our newly developed algorithm, simulative studies as well as real-world experiments using satellite broadcast television (TV) signals as NC signals to synchronize a high-resolution imaging radar achieving a timing standard deviation of less than 1.8 ps and a phase coherence for the X-band radar of less than 2° allowing interferometric or tomographic imaging principles to be used.