Research On Wireless Image Transmission Technology For Balloon-borne Observation System

The tethered balloon observation system(TBOS)is a new kind of observation platform.The load installed on it is a novel approach to realize the long period and remote observation.The wireless communication is considered as one of the important means of the image transmission between the load and the ground control center(GCC).In order to improve the reliability of the image transmission of the TBOS and its environmental adaptability,the designation and implementation of the wireless image transmission system of TBOS is studied.Based on the existing optical fiber image transmission,a flexible,high speed,stable and adaptable wireless image transmission leveling system is developed.According to the concept of software radio,the wireless image transmission platform of TBOS is designed and implemented,at meantime constructing the hardware platform which is combined with the related technologies,aim to develop a soft,flexible,open and easy to upgrade software radio platform.In order to realize the high speed,stable and portable image transmission,both ZYNQ+AD9361 hardware architecture and IEEE802.11 a physical layer of which based on orthogonal frequency division multiplexing(OFDM)are adopted.The platform combines the good system control performance of the ARM of ZYNQ,the real-time data processing capability of FPGA,the features of the full programmable AD9361 configuration and the characteristics of the anti-multipath fading and high frequency spectrum utilization of OFDM technology,and the advantages are complementary to achieve high speed,flexible and stable image transmission.In the FPGA part of ZYNQ,the digital interface with the AD9361 RF front end,the data channel of the processing system part of the ZYNQ,and the physical layer of baseband processor are implemented.The embedded Linux is transplanted on the ARM of ZYNQ's programmable processing system.The application development,physical layer management and data interaction with computer and the camera are completed for the AD9361 configuration.In the design of digital baseband processor,BPSK,QPSK,16 QAM and 64 QAM modulation modes can free switch for different requirements.The original structure of baseband processor is optimized and improved to save the FPGA resources and promote the efficiency of the processor.As the introduction of the wireless image transmission platform,it can carry out point to point image transmission between air tethered balloon observation platform and GCC,it also enhance the reliability of the image transmission.Experiments show that the communication system have advantages of flexibility configuration,high utilization rate and anti-multipath effect etc.thus it can be applied to a variety of complex environments.