Research On Image Data Transmission Of Telemetry System Based On Single Chip Microcomputer

With the upgrading of well-logging technology, image data transmission of telemetry system has developed rapidly.The increasing large capacity image data accurately transmitted to the ground system, which put forward higher request to the transmission rate of logging cable, so as to promote the development of high speed data transmission system.Traditional Manchester coding modulation mode, because of its lower transmission rate,is unable to achieve the real-time requirement of image data transmission. OFDM solves the problem of inter-symbol interference and bandwidth efficiency elegantly by using the orthogonality between sub-carriers, and has strong anti-interference ability and adaptive ability.High-speed data transmission can be achieved in a single core cable bandwidth limited by adopting OFDM.The main research work is image data transmission technology of telemetry system based on STM32 single chip microcomputer,which provides a theoretical basis for the production and application of the future.Telemetry image data transmission system designed in this paper adopts OFDM as the telemetry image data transmission system decoded-demodulation.The former deals with the collected image data from downhole by use of relevant coded-modulation and transmits them to the single-core cable through its interface. The latter processes the received data using relevant decoded-demodulation algorithm and restores the original image data. The main work is summarized as follows:1.The research background of telemetry data transmission technology is introduced. The latest research with existing problems of domestic and international is described and analyzed, and then explains the significance of this research.2.Single-core and seven-core logging cables commonly used in telemetry system are introduced and the transmission characteristic of single-core logging cable used in our system is emphatically analyzed. Then several main coding transmission ways on this basis are introduced and by comparison, OFDM is selected as the core technology in system design.3.The OFDM theory is introduced and analyzed detailedly.Then on this base the important system design parameters are determined and the basic structure of telemetry image data transmission system is presented.4.The STM32 with high performance in popularly is introduced and analyzed in detail and STM32F407 with excellent properties is chose as main control chip of the system.The hardware parts of the system is divided into power and clock module,D/A D/A and A/D conversion module, the JTAG interface module, camera interface module, Micro SD memory interface module and serial interface module.And the hardware design of each module is completed.5.The OFDM modulation and demodulation algorithms are analyzed in detail.The software designs of relevant modules and their simulation in VC++ are finished.Finally the whole software parts simulation of OFDM modulation and demodulation system is achieved.