A Full FPGA Implementation of Wide-Range Clock Distribution and Self-Regulating Synchronization

The next generation of high-energy physics experiments require clock distribution and synchronization systems with synchronization precision better than 10 ps. Recent studies have shown that the multi-gigabit transceivers (MGTs) in field-programmable gate arrays (FPGAs) can embed the clock into the serial data stream for transmission over appropriate optical links to achieve this level of precision. However, due to the inherent limitations of FPGA MGTs, the clock frequency that can be distributed over such links is restricted to a specific range, which may not meet the requirements of certain physics experiments whose distributed clock frequencies fall outside this interval. Additionally, it is highly desirable for the system to automatically maintain synchronization stability after link initialization or reset and during ambient temperature variations, without significantly increasing overall system complexity. To address these two challenges, this paper presents a complete FPGA implementation that enables the distribution of clocks over a wide frequency range with self-regulating synchronization. Since the proposed scheme relies on vendor-specific MGT architecture, it is applicable only to Xilinx FPGAs equipped with GTP, GTH, or GTY transceivers. However, as the implementation is fully FPGA firmware-based and does not require any external devices, it significantly reduces system complexity, making it easier to integrate into a variety of experiments that use these FPGAs.