Automatic Manipulation Of Frequency Discriminator For A Doppler Wind Lidar

Wind lidar is of great importance on measurement of global wind field and the change of wind velocities. Automatic manipulation is indispensable for common, stable, precise and efficient operation of wind lidar. The paper began with research on automatic manipulation of wind lidar. Firstly, the general manipulation scheme of wind lidar was illustrated. Secondly, the frequnecy discriminator was focused on and its automatic manipulation was designed and fulfilled. At last, feasibility of the control system was tested by experiments.The focus of the paper is the design and fulfillment of automatic manipulation of frequency discriminator which is an important part of wind lidar. Based on fulfillment of hardwares of the control system, the monitoring and controling software is programmed with Visual C++. The functions of this software included scannning the transmission of the F-P etalon by angle tuning, locating the F-P etalon on the workpoint, acquiring and processing the optical-intensity datas. Two key technics of the software were serial communication and GPIB communication. By serial communication, a singlechip will drive a step-motor and the F-P etalon can rotate to the position where the user wants. By GPIB communication, acquired intensity datas can be transfered to the master computer.The experiment was composed of four parts which were measurement and analysis of laser source, scanning of transmission curve of F-P (Fabry-Perot) etalon used in frequency discriminator, locating of workpoint position, measurement and analysis of hard object. The examining experiment of automatic controling system was advanced. The scanned transmission curve showed the same regularity to the theoretical one. The F-P etalon was located on the workpoint and measurement of the optical intensity was carried out. The measured result was 2.8% less than the data of this point on the transmittance curve, and the orientation error was less than 2.6μrad. The experiment testified the feasibility and precision of the automatic controlling system. On the worikpoint of F-P etalon, scattered signal of a hard object was measured. The hard object was set to be static, positive rotating and negative ratating. The measured rotate speed of the hard object were 5.1m/s and -3.9m/s respectively, compared to the data by tachometer measuring which were 4.7m/s and -4.3m/s. The result showed that the automatic-controll frequency discriminator can be used in the measurement of object speed.