【作者】 王兰炜；

【导师】 赵家骝；

【作者基本信息】 中国地震局地质研究所 ， 固体地球物理学， 2005， 博士

【摘要】 经过广泛而深入的调研,作者深刻地认识到大功率、人工源的超低频/极低频电磁波技术已经成为当今国际地球物理学界所瞩目的一个新兴的研究领域,并在地震监测预报、矿产资源勘探、核废料处理以及环境保护等方面具有广泛的应用前景。但是,在我国,目前人工源的超低频/极低频电磁波发射台的研究刚刚起步,还没有相应的超低频/极低频观测系统。本论文正是针对观测系统的研究而开展。经过详细、深入的研究,论文获得了以下的研究成果:1、研究总结了人工源超低频/极低频电磁信号接收的关键技术。人工源的超低频/极低频电磁信号观测系统的主要功能是在强干扰背景下接收、检测人工源超低频/极低频发射台发射的单一频率的信号,其关键在于采用相关检测技术和提高频谱分析的频率分辨率,最终提高信噪比。2、实现了对人工源超低频/极低频微弱信号的准确检测。虽然人工源的超低频/极低频发射台发射的信号功率很大,但经过远距离的传播后,功率会变得很小,从而被淹没在强背景噪声中,使得信号的信噪比很低。传统的检测方法对于这种微弱信号检测有很大困难,不适合于超低频/极低频观测系统。因此本项研究中采用了相关检测技术,通过软件完成互相关算法,在不增加设备硬件的情况下,实现了强背景噪声下人工源的超低频/极低频电磁波信号的检测。3、编写了应用于观测系统的频率细化计算处理软件。鉴于采用常规的FFT方法进行频谱分析时,如果频率分辨率要求较高,则运算量和存储量会显著增加的问题,论文中采用了基于复调制的频率细化技术,编写了应用于观测系统的频率细化计算处理软件,大大减少了FFT运算量和存储量,取得了很好的应用效果。4、研究分析了发射台信号频率抖动对观测精度的影响。通过数值模拟方法,研究分析了发射台信号频率抖动对观测精度的影响。据此,在观测精度要求一定时,可确定对发射信号频率稳定度的要求,或在发射信号频率稳定度已知时,可估计出信号的实际的观测精度。5、设计并研制了高灵敏度的感应式磁传感器。传统的感应式磁传感器(灵敏度约为100μV/nT)无法满足超低频/极低频观测的精度要求,论文在分析观测系统要求和功能的基础上,总结、分析了感应式磁传感器的设计理论,并提出了一系列设计原则和方法,成更多还原

【Abstract】 After reading a lot of papers related to Super/Extremely Low Frequency (SLF/ELF)electromagnetic wave, the author finds out that the artificial SLF/ELF electromagnetic wavetechnique today has become a new research field attracting much attention of geophysicistsall over the world and can be used to earthquake monitoring and prediction, reconnaissance ofresources, nuclear waste disposing and environment protection. However, the SLF/ELFtransmitter facility just starts to be constructed in our homeland, and there is no correspondingSLF/ELF receiver system. Therefore, this thesis focuses on the study of developing thesystem. Some important results are obtained as follows.1. Summarizing the key techniques of the artificial SLF/ELF. The main function of thereceiver system is the receiving and detection of electromagnetic signal from SLF/ELFtransmitter facility in the presence of strong background noise. For receiving techniques, itis crucial to use the correlation detection technique and improve spectral resolution.2. Detecting the weak SLF/ELF signal of known frequency. Although the power of thesignal from SLF/ELF transmitter facility is very powerful, it will become very weak aftera long distance transmission and submerge in strong noise, which often causes very lowsignal-to-noise ratio (SNR). Because it is difficult to detect the weak SLF/ELF signal inthe presence of strong background noise using traditional methods, the correlationdetection technique is used to optimize the SNR and carried out by the correlationalgorithm without any additional hardware. The test results indicate that the weak signalcan be detected very well.3. Programming the Zoom FFT algorithm suitable for the receiver system. The FFTalgorithm is widely used in spectral analysis for digital signal, but if the high resolutionspectrum is desired, more FFT points must be used, which is bound to result in the sharpincrease of data storage and operation of arithmetic. In order to solve this problem andobtain the given high resolution spectrum, zoom FFT with the technique of complexmodulation is used in the system, and the corresponding codes are written. The test resultsshow that it has dealt with the problems well.4. Analyzing the effects of instability of signal frequency on observation precision. By thenumerical simulation method, the effects of frequency shift on observation precision havebeen studied in detail. The results show that in order to get desired signal observationprecision, the stability of the signal frequency must reach a certain level. Or when thestability of the signal frequency is given, what the signal observation precision can bedetermined.5. Designing and developing high sensitivity induction coil magnetometer (ICM). Becausethe normal ICM (the sensitivity about 100 μV/nT) can not satisfy the observationprecision of the SLF/ELF receiver system, high sensitivity ICM is needed to be developed.On the basis of the analysis of the requirements and functions of receiver system, thetheory of ICM is summarized and a series of design principles and methods are proposedin the thesis. Then high sensitivity ICM is developed. After testing, the results show thatthe major specifications of ICM have achieved the level of the same products in the world:frequency ranges from 10 to 4000Hz;expanded frequency ranges from 1 to 10Hz;andsensitivity is 15mV/nT;The sensitivity can reach 150 mV/nT when combining with thereceiver system。6. Designing and writing the data acquisition and data processing software. The dataacquisition software used by measurement part and data processing software used by thesystem controlling part are designed and written using the assembly language and the VBlanguage, respectively. After testing, the results suggest that the software can be operatedeasily and conveniently and runs stably, which indicates the software is able to satisfy therequirement of long time and continuous work of the receiver system.7. Developing and testing the receiver system. The design scheme is proposed based on theanalysis of the requirements and key techniques of the receiver system. And the techniqueproblems during the development of the system are analysed and solved step by step.Then the receiver system is developed. Through test in field, the results show that thesystem specifications have achieved the design requirement, its major parameters haveachieved the level of the same products in the world: frequency ranges from 4 to 300Hz;resolution of spectrum can reach 0.001Hz and the dynamic range is more than 80dB,theminimum magnetic variation which can be detected is 0.01nT and the minimum telluricvariation is 0.5mV/km. The system runs stably and can be used for long time andcontinuous work in field.In the system test, the source is a simulated signal but not a practical one. So in the future,in order to improve the system, it is needed to receive the signal from the SLF/ELFtransmitter facility for a long time.更多还原