A New Network Synchronizer Using Phase Adjustment and Feedforward Filtering Based on Low-Cost Crystal Oscillators

A new network synchronizer using a two-way message exchange is proposed and implemented in a field-programmable gate array (FPGA). This synchronizer aligns its clock signal and time of day to that of the master node. For high-precision frequency control, a new phase adjustment method is employed, which efficiently provides high-frequency resolution and deterministic frequency control gain. In addition, a feedforward filter is used to reduce dithering of the time offset due to quantization errors in time-stamping. Even with a low-cost crystal oscillator, successful synchronization with root-mean-square (RMS) jitters of 0.1856 unit interval is achieved.