Pre-research Of Numerical Algorithm For Time Domain Electromagnetic System Transmitting Waveform

Time-domain Electromagnetic Method (Time Electromagnetic Method, TEM)isone of the commonly used measurement methods of geophysical prospecting.Because AEM geophysical prospecting method is rapid, low cost, large area, trafficand other features, are widely used in mineral exploration, basic geological survey,engineering, hydrology, environmental survey and other fields. Especially in thecoverage area of vegetation development or transport layer, it is more difficult toachieve the effect of conventional geophysical prospecting method. In this method,time electromagnetic system (TEM system) can be divided into airborneelectromagnetic (i.e. the time domain airborne electromagnetic) system and frequencydomain airborne electromagnetic system. From the angle of system carrier, can bedivided into fixed wing and helicopter AEM two. The ground TEM with a probingdepth, response curve shape is simple, abnormal high sensitivity and spatial resolutionadvantages, however the ground TEM in practical detection work, the need formanual laying and mobile transmit receive device for large area detection istime-consuming and laborious, low efficiency of detection, therefore, research onAero TEM is very necessary.This paper studies the time domain airborne transmitter current reduction bynumerical simulation, obtained the following research results in several aspects:1.According to the aviation transient electromagnetic acquisition device dataacquisition of the theory derived aviation transient theory induction current expressionof the electromagnetic anomalies in the coil, air transient electromagnetic transmittercurrent equation is deduced.2.On the formation of abnormal expression of the induced current coil theoryusing MATLAB simulation tools, the theoretical expression of aviation of transientelectromagnetic transmitter current is verified by simulation. 3. By shielding indoor simulation half air detection experiments, the acquisitionof anomaly induced current in the coil and the Fourier transform with the acquisitionof data, such as time and frequency domain transformation calculation, finally be partof transmitter current waveform, the theoretical expressions of further validation, theturn off time of transmitter current, pulse rate, and other important information.4. Using standard signal generator and collection device for signal collection,through the collection of data and signal generator, comparing the actual data andfinally established the transfer function of collecting device, signal acquisition unit isjust in this experiment to the phase change.5. Set uniform speed skip an abnormal coils with low resistance, closed loop andreal-time observation of induction current change and current data, draw the voltagecorresponding contour map, and keep the same altitude, through the acquisition of theinduced current waveform concluded that measurement precision of differentobservation position has certain influence on reducing emission waveforms, when airtransmitter coil with abnormal ground coil center, the largest induced currentamplitude, reduction of the transmitter and the actual current waveform minimumerror.6. By induced current on the measurement data of Fourier transform and inverseFourier transform, convolution calculation, the calculation of emission current peak,and is based on convolution extract waveform comparison emission current waveformand the actual launch.