Multi-user Acquisition Tracking Method Based On Liquid Crystal Optical Phased Array

With the increasing demand for capacity of communication,laser communication(Lascom)has become an ideal solution to spatial information network because of its advantages of large information capacity,low power loss,small divergence angle,strong anti-interference ability and strong anti-interception ability.Non-mechanical beam deflectors,such as optical phased arrays(OPA),make SWaP(size,weight and power-consumption)of the entire Lascom system smaller.Due to its light weight,inertia,and flexibility,this device overcomes many of the problems of mechanical beam steering.In order to construct a spatial laser networking system based on optical phased array,traditional ATP system can't adapt to the complexity of the system,and many problems need to be solved urgently.Multi-user tracking is one of these problems.Therefore,this thesis introduces a multi-user tracking method based on liquid crystal optical phased array(LC-OPA),which can realize the tracking of four beams simultaneously.This method includes a special algorithm for distinguishing multiple beams on a single CCD and a trajectory prediction method for calculating the position of the main lobes of each user.In theory,using this method,the system can quickly distinguish and locate each user and steer the direction of the beams separately.Then an experiment using the multi-user tracking method is conducted.In this experiment,two beams were successfully distinguished and the maintained at the target position simultaneously.Then two problems caused by the dispersion of LC-OPA is studied.Firstly,according to the multi-user tracking scheme,a dispersion effect occurs when different wavelengths of beams are incident on the same type of LC-OPA,and the deflection angles of these beams are different when the phased array is applied with the same voltage sequence.For this problem,the quarter-wave plate method is used to measure the voltage-phase curves of different wave.Secondly,in order to isolate the transmit and receive beams,the wavelengths of the two beams are usually different.And the difference in wavelength here will cause an error in the deflection angle.Then a simulation and an experimental are conducted for this problem.