Abstract
In electromagnetic sounding, the detection areas of time-domain and frequency-domain electromagnetic detection methods cannot be effectively connected, and the detection processes for these two methods must be implemented separately. To combine time-domain and frequency-domain electromagnetic detection methods and simplify the detection process, a time-frequency fusion transmission method is proposed to simultaneously excite the earth to produce transient and steady-state responses. By analyzing the characteristics of the time-domain and frequency-domain excitation current waveforms, a pseudorandom transmission waveform with dead time is designed, and a transmission system for a time-frequency fusion electromagnetic detection method is developed. In this detection mode, the pseudorandom transmission waveform contains several frequencies, and the transient induction field can be received during the dead time. The time-domain and frequency-domain responses can be obtained by the same procedure. At the same time, a self-adaptive pseudoload device is designed and matched with the corresponding control sequence to reduce the influence of dead-time. The experimental results show that the self-adaptive pseudoload transmitter can effectively reduce the current fluctuation, and the time-frequency electromagnetic transmission system can effectively excite the earth to produce transient and steady-state responses. The time-frequency fusion electromagnetic transmission method proposed in this paper can be used in electromagnetic detection instruments to improve the efficiency of electromagnetic sounding.
Highlights
Artificial field source electromagnetic detection plays an important role in mineral resource exploration, oil and gas resource exploration, geothermal resource development, geological engineering surveys, high-level radioactive waste disposal and other fields [1]–[6]
To realize a seamless connection between the detection areas in the time-domain and frequency-domain, improve the detection efficiency and focus on detection in transition areas covered by nonplanar waves, a time-frequency fusion electromagnetic transmission method is proposed, and a new pseudorandom time-frequency fusion transmission waveform is designed
This paper proposes a time-frequency fusion transmission method for electromagnetic sounding to solve the problems associated with the blind areas in the ranges of time-domain and frequency-domain detection
Summary
Artificial field source electromagnetic detection plays an important role in mineral resource exploration, oil and gas resource exploration, geothermal resource development, geological engineering surveys, high-level radioactive waste disposal and other fields [1]–[6]. The frequency-domain method transmits a continuous current waveform and obtains the resistivity distribution of different depths underground by collecting the amplitude and phase information of the electromagnetic field at different frequencies [9], [10]. To realize a seamless connection between the detection areas in the time-domain and frequency-domain, improve the detection efficiency and focus on detection in transition areas covered by nonplanar waves, a time-frequency fusion electromagnetic transmission method is proposed, and a new pseudorandom time-frequency fusion transmission waveform is designed. The proposed transmission waveform and transmission method can excite both the transient response in the time-domain and the steady-state response in the frequencydomain, improve the detection efficiency, and provide a new method to further develop the area of electromagnetic detection in general. The timedomain transient response and the frequency-domain steadystate response should be collected simultaneously in one detection process for time-frequency fusion electromagnetic detection
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