A simple Field Programmable Gate Array (FPGA) based high precision low-jitter delay generator

Abstract

Pulse delay generators are ubiquitous in laboratories to coordinate and control the timing between different devices in applications that include lasers, mass spectrometers, and other scientific instruments. The most important required characteristics are precision, to control time exactly, and low-jitter, to minimize uncertainty in experiments. Here, we introduce a new design of a high precision and low-jitter digital delay generator based on a Field Programmable Gate Array (FPGA). The final delay is composed of steps of 4.2 ns (coarse delay) with fine steps of 16 ps (fine delay). The coarse delay is generated by a 240 MHz pulse sequence from the FPGA with a 50 MHz clock. An embedded time-to-digital conversion unit is used to measure the interval between the external trigger and the clock signal, which, together with an integrated delay generator, is used to realize the fine delay. Jitter compensation is achieved through a measurement-and-feedback module. A computer interface is designed to control the system through a Nios II processor. Measurements confirm a time resolution of 16 ± 2 ps with jitter below 450 ± 20 ps (at 24 °C) with a maximum delay of 1 s. The whole system is simple in structure and low in cost.