Research on Frequency Discrimination for a Doppler Wind Lidar
|School||Harbin Institute of Technology|
|Keywords||Lidar Doppler frequency shift wind double-edge technique F-P etalon|
The change of winds velocities in lower atmosphere is the most dangerous factor during the flying-off and landing of aeroplane. So it is important for us to detect the change of winds in order to escape actively. We can classify the lidar as coherent and incoherent (direct-detection) lidar on the base of operating principle. In this dissertation I use the Fabry-Perot double-edge technique to detect the Mie scattered signal. Considering the movement of atmosphere aerosol and molecule, when the laser is operated at 1.06μm, the Rayleigh backscattered signal of atom-sphere particles is almost zero, the Mie scattered signal of aerosol is relatively intense, so this brings many advantages to the detection of signal. The frequency discrimination system is one of the pivotal techniques for Doppler winds measurement Lidar. It can analyze the frequency shift from the variety of intensity. And the capability of frequency discrimination will influence the sensitivity of winds measurement of Lidar.This disseratation mainly studies the frequency discrimination system of winds measurement lidar. The double-edge detection theory for scattered signal of aerosol in lower atmosphere is deduced, the interaction of atmosphere and the laser beam during the transmission and all kinds of disturbing signals of the return signal are analyzed here. I simulate the return signal and the transmission function of F-P , choose the appropriate parameter of F-P based on their influence of the sensitivity of the system, and simulate the process of frequency discrimination. At last, I analyze the response, sensitivity and errors of the system according to the simulant data, and correct the simulant results.I also design the experimental platform of data acquisition system and the data collection of the result of simulation with the NI DAQ. I choose appropriate DAQ by the measurement accuracy demand, set every parameter of DAQ and empolder the collection program on the basis of the characteristic of signal. Then I collect the simulant return signal. The data acquisition system designed in this experiment can achieve the work of collection.