Design And Implementation Of Data Acquisition & Calculation System For Spot Position Detection Based On The Quadrant Detector

Atmospheric laser communication has gradually become the current research focus, owing to own the advantages of great anti-interference ability, high security, large capacity of communication, etc.. In the atmospheric laser communication systems, the ATP technology of high precision and high automation is one of the key technologies for the successful establishment of the space optical communication link and the guarantee of the great communication quality. For the spot position detection in ATP, the four-quadrant detector has distinct advantages. According to deal with the four quadrant detector output signal, this paper has designed a high accuracy synchronous data collecting and processing system, which can be provided real-time spot position for the ATP system, and has functions of the computer memory for the original data. The main research contents include:1. In this paper, the principle of the four-quadrant detector spot position detection is introduced, the requirement of four-quadrant detector data collecting and processing system is analyzed, and the system based on the FPGA+DSP+USB 3.0 architecture is proposed, combining with the actual application requirements of atmospheric laser communication.2. Based on the analysis of the needs for data collecting and processing about four quadrant detector light spot position detection, at first, the full differential front end sub conditioning circuit is designed, and can improve the system anti-interference ability and compatibility; and then the 24 bits, 4 channels, synchronous data acquisition, ΔΣ type digital to analog conversion chip is achieved. The four synchronous acquisition data function is accomplish by controlling the FPGA, and the performance of the acquisition system is improved through the calibration error and reasonable wiring, etc.; finally, the hardware design of real-time processing module has been completed by utilizing the powerful digital signal processing ability of the DSP, and on the basis of the spot position solution algorithm, it can be provided 10 kHz real-time spot position information for the ATP system.3. The USB 3.0 core circuit board is redeveloped on the basis of the in-depth study of the USB 3.0, the function of high speed original data storage for the four-quadrant detector is completed. Firstly, combining the USB 3.0 core circuit board with the real-time processing module, the whole hardware design is completed; and then according to the system’s requirements of data volume and flexibility, the data buffer system design is achieved by considering the DDR II as the FIFO; Finally, the USB 3.0 chip firmware should be redesigned, the USB 3.0 control logic and the upper computer program are completed, and the function of data storage is implemented.4. At first, the effective resolution and synchronism of AD are tested by using the accomplished system, and the effective resolution of 18 bits is achieved. Then, the delay test of real-time processing module are finished, the delay time reaches 10μs; at last, the transmission rate of the USB 3.0 module is tested, and the highest speed is 92MB/s without error.