Abstract: In order to solve the inaccurate result of the external factors in the actual measurement of laser
ranging, a kind of echo simulation system is designed to test the measured results. The ranging system emits a
narrow pulse width laser to the echo system, the PIN (Positive Input Negative)pairs perform laser acquisition
and the photoelectric conversion, and the electrical signal is sent to the FPGA ( Field-Programmable Gate
Array). The FPGA carries on the 15 times frequency operation through the built-in PLL(Phase Locked Loop)
and carries on the high precision time delay. The laser actuation part utilizes the MOSFET (Metal-Oxide-
Semiconductor Field-Effect Transistor) tube switch nature to produce the narrow pulse signal and the laser
modulation simulation actual measurement the Echo laser. Finally, the simulation result is obtained in the
ranging system. The results show that the stability of the system is high by measuring the same distance multiple
times and different distances. Precision can be achieved 0. 17 m and error is 0. 03 m.

Key words: phase locked loop(PLL), echo simulation, metal-oxide-semiconductor field-effect transistor(MOSFET), laser ranging