| With the rapid development of science and technology,human society is rapidly entering the era of automation and intelligence.All kinds of intelligent systems are gradually integrated into our life,which provides great convenience for our life.And many intelligent systems are inseparable from the corresponding detection equipment.As a kind of radar technology,Lidar has higher detection accuracy and anti-interference than traditional radar.It is widely used in intelligent robot,map modeling,unmanned driving and other fields,so the related research has great social and economic value.As a new type of beam pointing control technology,Optical Phased Array technology OPA(Optical Phased Array)has become the hot topics in the study of solid state laser radar.Based on thermal light effect of waveguide phased array is by controlling the load in the optical waveguide medium under the heat generated by the current or voltage,to change the real-time temperature of the waveguide,and transform the refractive index of the waveguide,eventually leading to the beam of the waveguide of phase change,in order to realize beam scanning.Therefore,it is a very key part of optical phased array to design the corresponding phase drive circuit with high precision and controllable output.The driving circuit of constant current source studied in this thesis is used for optical phased array based on thermal-optical effect.The temperature of the medium is controlled by controlling the current loaded between the medium of the waveguide,so as to control the refractive index of the waveguide and finally realize the scanning of the beam.Because the traditional constant-current source circuit usually has the disadvantages of complex circuit structure and high cost,it cannot meet the requirements of high precision and multi-channel output.In order to meet the requirements of optical phased array phase drive,a 128-channel constant current source driver circuit based on field programmable logic gate array(FPGA)and closed-loop feedback regulation principle is designed and implemented in this thesis,which is used to drive and control optical phased array phase control unit.The whole circuit is mainly composed of FPGA control module,DAC data conversion module,ADC data acquisition module,ADG analog switch module and sampling resistance.During the test,the upper computer is used to set the regulation parameters of the corresponding channel.The FPGA control module receives the regulation parameters and controls the DAC module to output them.At the same time,ADC module collects the output and adjusts the collected data in FPGA to achieve the controllable constant-current output of 128 channels.The current control range is 0～15m A,the step size of control is 0.05 m A,and the precision of control can reach 0.02 m A.Finally,the stability and accuracy of the output current of the system are tested,and the test results are analyzed.The performance test data of the system show that the optical phased array phase drive circuit designed in this thesis has the advantages of high output precision and good stability,and can meet the requirements of optical phased array phase drive.On the basis of analyzing the error sources,the further optimization direction of the output performance and structure of the system is pointed out. |
