Research Of TDR Technology Based On Equivalent Sampling

Time Domain Reflectmentory is an electronic measuring technology. In the past years, TDR was used to monitoring kinds of states and space position of objects, taking locating aerocraft as an example. In the 1980s, TDR was used for Engineering geological exploration and monitoring abroad. It was especially outstanding in coal geology and used for monitoring deformation of underground coal seam and rock. American researchers applied TDR on monitoring deformation of mountain and soil because of landslide until the middle of 1990s and made plenty of rock and soil landslide experiments.Recently, TDR has been widely used to prevent geological disasters, forecast landslide and analyze water content in soil because of its convenience, safety, digitization and remote monitoring. Monitoring landslide with TDR, we can master the dynamic process of deep landslide deformation, monitor landslide deformation dynamically and provide reliable data for monitoring landslide and forecast research. Researchers and the governments pay much attention to the study of TDR application abroad, but it's just the beginning in our country.A complete TDR monitoring system contains coaxial cable, cable tester, data recorder, remote communication equipment and data analysis software, and cable tester is the key. Now, most TDR systems use 1502C/CS of Tektronix Co. and TDR100 of Campbell Scientific Co., but these products are expensive and need supporting facilities, which is not conducive for popularizing TDR. Therefore, owning TDR instrument of our own intellectual property rights is the only way of getting rid of foreign expensive TDR instrument, popularizing TDR application and protecting our people from geological disasters.This thesis introduced the basic theory of TDR application after its application development, obtained theoretical calculation model of TDR monitoring system based on studying electromagnetic wave transmission in medium, analyzed the incidence and reflection process of pulse signal in coaxial cable and computed the reflection coefficient. Finally, designed a prototype independently. First, the prototype sent a pulse signal to the coaxial cable. Then, collected the high-speed echo signal with sequence equivalent sampling principle and displayed both the detection pulse signal and the echo signal. Finally, TDR system located the distortion point according to the time difference between the detection pulse signal and the echo signal. Meanwhile, determined deformation type of coaxial cable by analyzing echo signal status.Otherwise, the thesis made plenty of detecting real distortion points experiments with the TDR prototype. By comparing the results with the real data, validated the rationality of calculation model and the reliability of TDR prototype.The thesis is made up of five chapters and the main contents are follows:Chapter 1 introduced the development of TDR, analyzed the status and development trend of TDR, detailed the testing principle and engineering implementation of TDR application on monitoring landslide, explained how to choose coaxial cable according to engineering status and described research significance and main research contents finally.Chapter 2 introduced advantage, structure and signal transmission characteristics of coaxial cable, analyzed coaxial cable equivalent circuit and uniform transmission line equation, obtained expressions of uniform transmission line characteristic impedance, traveling wave and reflection coefficient, explained reflection coefficient and TDR monitoring calculation model, summarized the principle of TDR monitoring system, and finally described the principle of coaxial cable impedance matching and its importance.Chapter 3 designed a prototype based on TDR monitoring calculation model, gave the design program of TDR monitoring system hardware, detailed function modules and pointed out the key of the whole system design.Chapter 4 introduced software design of TDR monitoring system, described system testing and parameter setting boards and using the software and detailed function modules of TDR monitoring software.Chapter 5 and chapter 6 summarized, compared and analyzed the results, validated the reliability of TDR monitoring system and the correctness of the calculation model and made prospect of work in the future.