Phase Synchronization Concept for the Bistatic Extension of the Airborne F-SAR System

The requirements for future synthetic aperture radar (SAR) systems are evolving towards bistatic and multistatic acquisition modes with distributed transmitter and receiver systems. However, due to the underlying physics in the radar signal processing, especially for SAR interferometry, phase coherence and hence phase synchronization are essential for the development of such systems. This work analyses and proposes an optical synchronization link for the bistatic extension of the existing airborne SAR system, called F-SAR [1] from the German Aerospace Center at L-band frequencies $(\mathbf{1. 3 2 5 ~ G H z})$. The use of time-to-digital converters reduces the complexity of the system, the data rate, and the frequency interference in comparison to existing methods and provides a general approach to synchronize without committing to a specific microwave frequency range. To prove the feasibility, a custom RF-measurement board is developed and hardware tests are performed in the laboratory achieving phase synchronization better than $\pm 5 \mathrm{ps}\left(\pm 2.5^{\circ}\right)$.