Abstract: This paper describes the trouble and the limitations of common sampling on the transient pulsant signal. To solve these troubles, this paper mainly introduces the theory and example design of digital forward sampling. The delay of the key signal in an analog circuit is substituted by a technology called’forward circulatory storing’ in the digital circuit. We can get the whole pulse of the input signal and keep the signal integrality synchronously thanks to the digital forward sampling theory. This design is validated by FPGA simulation and used in the work of “Transient Pulse’s A/D Conversion”. This conversion system can store 4kbyte data with the rate of 500Mbyte/s by the best FPGA we have chosen.

Key words: transient pulse, forward sampling, digital, FPGA