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Some Key Technologies of Ultra-wideband Electromagnetic Logging

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Tutor: ZhouKaiBo
School: Huazhong University of Science and Technology
Course: Detection Technology and Automation
Keywords: UWB electromagnetic,UWB antenna,FDTD
CLC: P631.81
Type: Master's thesis
Year:  2011
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Abstract:
Modern technology to detect electromagnetic logging depth resolution and detection of high demands made, ultra-wideband electromagnetic waves to detect a good solution to the conflict between depth and resolution of relationship is important to study the future direction of electromagnetic wave logging.The thesis introduces the research background, purpose and meaning and ultra-wideband electromagnetic well logging technology and international research status and development prospects; according to the definition and ultra-wideband electromagnetic wave propagation theory that electromagnetic pulse signal of UWB advantages, respectively, from depth resolution and detection of two ultra-wideband electromagnetic waves in lossy medium, the propagation characteristics of formation and found that different signals have the same bandwidth and transmit power, increasing the percentage of the signal bandwidth, increase the relative detection depth, to improve detection resolution to resolve the contradictory relationship between them provide a theoretical basis; and then the finite element method and moment method, combined method of transient electromagnetic field theory and the ultra-wideband electromagnetic wave propagation characteristics in the formation, respectively, over broadband spiral antenna and dipole antenna design and simulation analysis, simulation results show that within the band width they have a good radiation characteristics. Mainly in the analysis of the traditional rectangular microstrip antennas, based on the rectangular patch on the ladder-type and in two symmetrical patches on the cracks opened, as well as the shape of the antenna¡¯s ground plane, the authors designed a new type of asymmetric logging butterfly antenna, the antenna by HFSS software simulation and optimization, the relative bandwidth of the antenna 86% (VSWR <2.0), covering the frequency range 500MHz ~ 1.25GHz, has a good omnidirectional characteristics and produced a kind of microstrip antenna, the use of vector network analyzer on the antenna performance test, the test results and simulation results are in good agreement.Finally, the use of ultra-wideband electromagnetic FDTD simulation of the propagation characteristics in a typical formation, through the analysis of simulation results to determine the transmission power of UWB electromagnetic waves, characteristic bands with different media, the correspondence between parameters, to the late log interpretation provide a theoretical basis.
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