The Study On Pseudo-random Multi-frequency Electromagnetic Prospecting System

Pseudo-random multi-frequency (PRMF) signal is invented and named by academician He Jishan. The bandwidth of PRMF signal is controllable, it's energy concentrates on several frequencies, which are equally spaced on log scale coordinates. It is ideal excitation source for electrical exploration. PRMF electromagnetic exploration method with PRMF signal as excitation signal, not only have time domain electromagnetic method's advantages of high work productivity, acquiring plenty information in single measurement, but also have frequency domain electromagnetic method's advantage of super anti-interference ability, and portable instrument. In this dissertation, based on the study of dual-frequency induced polarization (IP) surveying system and pseudo-random tri-frequency IP surveying system, PRMF electromagnetic survey system is studied systematically, including PRMF signal, PRMF relative phase IP, using computer simulation for design and evaluation of electrical instrument, digital signal processing of PRMF electromagnetic signal, transmitter for PRMF electromagnetic method, receiver for PRMF electromagnetic method, analysis and realization of data acquisition software for PRMF electromagnetic method, and so on..In the study of PRMF signal, based on characteristic of PRMF signal, the expression of PRMF signal in time domain and frequency domain is found. By comparing the spectrum and power distribution of PRMF signal and square wave, which is widely used in ordinary electrical exploration, the advantage of PRMF signal as current source of frequency electromagnetic method exploration, as high work productivity, high power supply utilization ratio, portable instrument, high precision, is proved. It's a ideal waveform for electrical exploration.Based on relative phase IP method, the relative phase spectrum IP method is developed. The formula of relative phase spectrum is defined. The relative phase measurement does not need synchronization between receiver and transmitter, and carry out one order correction forelectromagnetic coupling in IP. PRMF relative phase spectrum IP method with PRMF signal as excitation has the same advantage of relative phase IP method, and offer rich information for the discrimination of anomaly source. Relative phase spectrum and phase spectrum of representative Cole-Cole IP model show that relative phase spectrum have the same ability as phase spectrum to the detection of anomaly. Field experiment result proves that PRMF spectrum have the ability to suppress electromagnetic coupling. PRMF relative phase spectrum IP show the advantage of PRMF signal as source of electrical exploration, can play important in groundwater exploration, mineral exploration, and so on.Computer simulation technology is widely used in analysis, design, and optimization of complex control system in field of astronautics, radar, electrical power, and so on. Using traditional method develop electrical instrument face the problem of long develop period, high cost and great risk. To overcome above problems, computer simulation method is used in design, optimization, and improvement of electrical instrument. The simulation of dual-frequency IP instrument, relative phase IP instrument and new generation electrical instrument based on digital signal processing show the importance of computer simulation in design, optimization, and improvement of many kinds of electrical instrument. By using simulation in electrical instrument development, period, cost, and risk of electrical instrument development can be greatly reduced.Digital signal processing will get wide application in different kind of electrical instrument. In this dissertation, effective digital signal processing method used in electrical exploration is developed, and used in new developed PRMF electromagnetic survey system successfully. By using digital signal processing method, not only realize multi-frequency IP method, but also realize multi-frequency electromagnetic method and other electrical prospecting methods in a instrument. At the condition of no ha...