| With the rapid development of short video,interactive games and other applications,people have higher and higher requirements for data transmission of high speed real-time signals.Wireless laser communication has many advantages,such as high bandwidth,hard to steal and unitary,etc.,and it is suitable for special environment.It is one of the most promising candidate transmission technologies for future high-speed communication.With the research and development of laser,modulator,detector and demodulator,the popularization of wireless optical communication system with high speed and high bandwidth becomes more and more possible.Hope to provide real-time,stable,high-speed video transmission services for the vast number of users.This thesis studies the wireless laser high-definition video transmission technology,and designs a set of wireless laser high-definition video acquisition and transmission communication system based on field programmable gate array(FPGA).The system uses OV5640 camera as the front-end video data acquisition source.Under the drive of pixel clock,the field synchronization signal,line synchronization signal and 8-bit data output by the sensor are converted into write enabling signal and 16-bit write data signal of SDRAM read-write control module.The SDRAM read-write control module is responsible for driving the SDRAM off-chip memory,caching the image data output by the image sensor,and finally encapsulating the complex SDRAM read-write operation into a FIFO user interface.The image data packaging module is responsible for reading 16-bit image data from SDRAM and converting it into 32-bit data convenient for call by the Ethernet sending module.The frame header of the image data is added.The module controls the number of bytes sent by the Ethernet sending module and sends one line of image data at a time.It is used to cache the image data to be sent,and add a frame header when sending ten packets to reduce the error rate of transmission information.UDP module realizes the transceiver function of Ethernet communication.This module calls the Ethernet receiving module,Ethernet sending module and CRC32 verification module internally,realizes the conversion of 32-bit data and 4-bit MII interface data,and finally realizes the whole process of image data acquisition,storage,packaging and real-time transmission in the FPGA development board.OPA690 is an amplifier control chip for laser op amp driver.It adopts voltage feedback and control op amp,and can be directly supplied with DC power supply + 5V voltage.OPA690 drives a 1V to 4V output voltage,output 150 m A drive current,can reach150 MHz drive bandwidth,and the internal structure of the chip system provides the highest rate of power conversion,so OPA690 is used as the driver chip of the laser drive circuit.OPA657 internal by junction field-effect tube input stage,such as high gain voltage feedback amplifier stage and output power structure,make its very high input impedance and the load ability is very strong,has low noise,fast response and high sensitivity,junction field-effect tube next to nothing in the process of the input current noise,amplifier module of amplifier chip as the receiving end.In this system,UDP transmission protocol is adopted,and Gigabit Ethernet is used to connect FPGA development board and wireless laser system.After debugging the display end of the upper computer,the wireless laser video transmission system designed and completed by myself is tested as a whole.Signal Tap II technology was used to verify the online logic of digital circuits,and Wireshark network analyzer was used to analyze the data capture packets received by the data capture packet technology.At the same time,continuous video transmission tests were carried out under stable weather conditions.The test results show that the system can operate normally in high-definition and stable without obvious dragging of video frequency data.The communication system solution provided in this paper is reasonable and feasible. |
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