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Research on speckle noise of laser Doppler velocimeter for the vehicle self-contained navigation
Authors:Jian Zhou  Xiaoming NieXingwu Long
Affiliation:College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Abstract:A novel multipoint layer-type laser Doppler velocimeter (MLLDV) is designed to measure the velocity of a vehicle for the self-contained navigation system. In order to investigate the speckle's influence on the Doppler spectrum, formulas of time-lagged covariance and speckle broadening were derived for our MLLDV. Simulations and experiments are made for detailed analysis. The results show that the time-lagged covariance of photocurrent is directly proportional to the incident angle, and is inversely proportional to the elevation fluctuation of the ground together with the velocity of the vehicle. Speckle broadening is a function of the vehicle's velocity, the 1/e2 Gaussian spot radius and the phase correlation length of the ground. For our MLLDV, Doppler frequency and Doppler broadening are both directly proportional to the velocity of the vehicle. Besides, the ratio between Doppler broadening and the corresponding Doppler frequency is about 0.72% when the speed of the vehicle varies from 0 to 9.6 m/s.
Keywords:Multipoint layer-type laser Doppler velocimeter   Speckle broadening   Vehicle-mounted self-contained navigation system
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