A programmable delay line

The paper describes the design and test results of a programmable digital delay line implemented in an FPGA device (Kintex-7, Xilinx). The operation of the delay line is based on the modified dual interpolation Nutt method that combines two actions, i.e.: (1) counting the periods of a reference clock and (2) time interpolating within a single clock period. The first action provides an extremely wide range of the introduced delays (> 9 minutes), while the second one allows reaching relatively high delay resolution (2 ns) with a timing jitter as low as 35 ps (until delay of 1 μs). The high metrological parameters of the designed delay line are achieved at the expense of increased difficulty in implementation of the method in an integrated circuit. The major problems to be solved were the synchronizations of input signals as well as synchronous and asynchronous parts of the system, which were effectively provided with the use of two dual-edge synchronizers, a clock signal logic level detection system and associated synchronizers.