【作者】 陈健；

【导师】 林君；

【作者基本信息】 吉林大学 ， 测试计量技术及仪器， 2012， 硕士

【摘要】 时频电磁法包括大地电磁法、可控音频大地电磁法和瞬变电磁法，是通过天然或人工产生的电磁场研究地球内部介质的电性结构的地球物理方法，被广泛应用于金属与非金属矿床、油气田、地下水等资源和能源的勘查以及地震等自然灾害的监测。本文以宽频带、低噪声采集为研究目标，以高精度模数转换技术（Δ-Σ技术）、GPS授时同步技术、大规模可编程逻辑技术（FPGA）、固态硬盘存储技术、高性能低功耗处理器、信号处理技术为基础，参考国外先进多功能电磁法仪器设计，研制出宽频带时频电磁法接收机样机。利用全波采集、双极性叠加方法，实现时频电磁法接收机的瞬变电磁接收；利用自动扫描、整周期采集技术，实现可控音频大地电磁法高效率施工、相关参数准确获取；利用高采样率采集、数字滤波抽取的方法，实现大地电磁宽频带、长周期的采集。自主研制的科研样机应用于松江河地热勘探、大台沟铁矿探测等可控音频大地电磁野外实验，取得了与地质结构相符的结果；进行了室内瞬变电磁模型实验以及室外对比实验，验证了仪器的低噪声，并与商业化瞬变电磁仪的指标进行了对比；在长春孙更屯进行了大地电磁测量，与早期凤凰公司的V5产品所测得的结果一致。更多还原

【Abstract】 The current situation is that geophysical equipment such as electromagnetic instrument heavily depends on imports, and instrument developed has not been given attention for a long time. Development Plan Outline for Medium and Long Term Science and Technology Development （2006—2020） suggest that the demand of time‐frequency electromagnetic Instrument will be a further increase, so it is pressing to develop it with freedom knowledge property right and excellent performance for the healthy development of geophysical exploration in our country. The rapid development of high‐precision analog‐digital conversion technology, GPS timing technology, solid‐state disk storage technology, high performance processor, signal processing technology will help to deal with key technologies such as high‐frequency weak signal detection and extraction,1/f low‐frequency noise removed, synchronization trigger for remote sending and receiving, real‐time storage of large data amounts, so it is feasible to develop broadband electromagnetic receiver.Started with the principle of TEM, CSAMT, MT, collected and compared with technical specifications of the foreign instrument, designed by modular concept, electromagnetic receiver is made of a control board, five high‐frequency board, five low‐frequency board. The control board is based on USB2.0transfer protocol, and control FPGA controller through microcontroller bus, which includes SLAVE controller, large‐capacity FIFO controller, SPI bus converter, GPS information converter, synchronization trigger and calibration signal transmitter. The control board has solved the problem of high‐speed data transmission by combination of slave FIFO and large‐capacity FIFO. Slave FIFO is combined with USB2.0microcontroller and main controller simulated by FPGA. Large‐capacity FIFO is made of SRAM and small scheduled FIFO which is integrated in FPGA. In order to decrease crosstalk, the communicate of each functional board and control board is completed by magnetic coupling isolation, and reasonable layout, shielded, ground handing, power isolation is used too, which can decrease interference and reduce noise.On the basis of analyzing how to decrease1/f noise by chopper technology and Δ‐∑technology, the low‐frequency board achieve targets that1/f noise corner frequency is lower than0.1Hz, and amplitude spectrum of frequency lower than corner frequency is less than10‐8uV. Through the experiment of signal test, short circuit test, sensor matching test, the low‐frequency board can be used in the acquisition of a large dynamic range, which includes MT, LOTEM and CSAMT. It also verify the long‐term reliability and standability of the low‐frequency board. After designed high‐frequency acquisition boards based on AD7763and AK5394, it verify the advantages of the AK5394through noise test and sensor matching test.The final design of the high‐frequency board has achieved these target that the peak‐peak value of noise is less than10^‐7 uV and amplitude spectrum less than10^‐7uV, so the acquisition of AMT, TEM and CSAMT can use high‐frequency board. The successful design of the low and high frequency board laid the foundation of broadband low noise acquisition.Because of non‐consisitency caused by component differences, the calibration souce and synchronous clock board generates1V peak value by GPS PPS trigging benchmark source chopper and analog amplifier operation circuits, in order to providing calibration source for low and high frequency acquisition. It also integrates circuit of OXCO synchronization and GPS synchronization, which is combinationed with FPGA to achieve line trig, gps trig and OXCO trig.Three electromagnetic methods of Data recording and storage strategy has been analyzed in detail. On the basis of thorough analysis of the TEM signal characteristics, TEM data recording is achieved by binary full waveform records and bipolar overlay method of handing. A series of basic logarithmic interval frequencies used for CSAMT is designed by the advantages of the whole cycle of acquisition. CSAMT sweep data is automatically recorded by tbl table completed by own TBLEditor softeware. After analysis of the relevant characteristics of the MT signal,the MT recording method is full‐wave acqusisition by2000Hz, and then PC104generates time series data of125/2Hz,125/64Hz and125/2048Hz by digital filter and extract.The right of time‐frequency electromagnetic design is verified by the experiment in Jilin Changbaishan geothermal resource exploration, Liaoning Dataigou iron mine explortation, Changchun Cultural Square, Changchun Sungengdun and so on. Compared with similar instruments on the market today, it has a great advantage.更多还原