Abstract: In order to achieve high-precision ground detection of time sequential signals of aerospace equipment, a special ground test system based on field programmable gate array (FPGA) is designed, and time-to-digital converers (TDC) is the key component of the system. The circuit adopts digital interpolation technology, where high-frequency clock is used to directly count for “coarse” measurement to ensure the measuring system range, and “fine” measurement is achieved by latching the phase shift clock level at the edge of the signal to be measured to improve the measurement accuracy. The sources of measurement errors is analyzed and the corresponding solutions are put forward. Through experimental verification, it is shown that the measurement resolution of the circuit meets the design value of 0.2 ns, and the measurement uncertainty caused by the repeatability is less than 0.1 ns. The circuit has high measurement accuracy, good flexibility and convenient design, and can meet the application requirements of related detection systems.

Key words: ground test system, time interval measurement, field programmable gate array, time-to-digital conversion circuit