Research On Doppler Measurement Based On Microwave Modulated Laser Technologies

Laser Doppler measurement techniques have been widely used in the measurements of the relative velocity of the target and the detection of the atmospheric wind velocity and other fields,because of their several advantages: contactless measurements,fast response and excellent spatial resolution. This thesis develops a new technology for Doppler measurement with microwave modulated laser technologies. In which laser as carrier was intensity-modulated by microwave signal, transmitted the signal intensity was directly detected by the receiver on a movement platform. Through the detection of the microwave signal Doppler frequency shift, achieve the relative movement speed measurement.Compared with the traditional laser heterodyne technique, because Doppler measurement did not need to directly identify the laser frequency shift, the limitation of laser with narrow linewidth and high frequency stability were relaxed. Meantime, 1m/s corresponds to 5.9Hz Doppler frequency shift while 1000 m/s corresponds to 5.9KHz Doppler frequency shift at microwave modulation frequency 1.772 GHz. The technique is easy to measure high-speed relative motion.A system of microwave modulated laser velocity measurement was designed and developed in this thesis. In this experimental system, both transmitting system and receiving system were needed. And then, Experimental research was made to measure to the relative velocity in the Laboratory with the measuring range 0.1m/s~0.21m/s. the average velocity as the third party data was calculated by measurements of the movement distance and time, which was used to compare with velocities calculated by Doppler shift. The results show that the velocities calculated by Doppler shift are in good agreement with the third party velocities with a mean measurement relative error of 1.1%. The experimental results verify the reliability of the relative velocity measurement by microwave modulated laser technologies.