Research On The Transmitting Method And Technology Of Shallow High-resolution Ground-airborne Frequency Domain Electromagnetic

The SAEM(semi-airborne Electromagnetic Method)is an efficient electromagnetic detection method that the transmitter is placed on the ground and the receiver is hoisted in the air by the UAV.Combined with the advantages of large depth of ground electromagnetic detection and high efficiency of airborne electromagnetic detection,the SAEM(semi-airborne Electromagnetic Method)has the advantages of high efficiency.It has the advantages of economic,higher efficiency,larger depth,higher resolution and applicability for complex landscape area.At present,the medium frequency(30-3000hz)has achieved good results,and is widely used in the exploration of resources and minerals,engineering geology and detection of complex terrain environment.However,with the development of society and the rapid progress of urbanization,there are some new problems in the electromagnetic detection system in the frequency domain of the ground and space,which mainly focus on the detection of the shallow area of the stratum.Under the existing technical conditions,it is challenging to solve these problems.Due to the weather or the battery life limit of the rotor UAV,the UAV flight time and times in the air become very limited,so that the receiving system needs to carry out efficient acquisition.The goal of this project is to choose the appropriate electromagnetic emission scheme.The bandwidth of electromagnetic wave frequency point is widened,the number of electromagnetic wave frequency points is increased,thus the longitudinal resolution of detection is increased,and the shallow high-resolution detection is realized.The main contents of this paper are as follows:1.This paper studies the characteristics and advantages of different emission sources in the ground to air electromagnetic exploration,and determines the type of emission sources used in this study.The transmitting circuit model is established,and the parameters of the electrical components in the circuit model are calculated from the actual parameters.Through the circuit simulation,the transmitting effect of the ground air joint electromagnetic detection electrical source and the large loop line source is obtained.Through the matlab program,the electromagnetic field distribution of long wire source and large loop wire source is simulated.This paper compares and analyzes the emission effects of long wire source and large loop wire source in the ground air joint electromagnetic exploration,and selects the electrical source as the emission source of this paper through comprehensive comparison.2.According to the definition of skin depth,the relationship between the transmitting frequency and the detection depth of the shallow high-resolution ground-airborne electromagnetic detection is calculated.Then the layout method and antenna design of the transmitter are studied,and the relationship between the length of the transmitter and the electrical parameters is discussed.Finally,the relationship between the electrical parameters and the detection range is discussed.3.The calculation method of emission energy is given,and the minimum emission current required in field exploration environment can be obtained.According to the transmitting requirements and parameter settings of this project,the appropriate transmitting machine parts are selected,and the physical welding is completed,and the waveform of electromagnetic wave emission of this project is selected.4.The output waveform of the(electric)bridge is simulated and the FFT transform is carried out.The transmitting scheme(has been)made,the circuit is(has been)debugged,the output results of the measured bridge is consistent with the simulation results,the expected transmitting target is achieved,and the pseudo-random waveform which can meet the requirements of high-resolution surface to air electromagnetic detection is successfully transmitted.In this paper,we studied the method and circuit design of electromagnetic emission for shallow high-resolution electromagnetic detection,compared the emission effect of different types of emission sources,and selected appropriate electromagnetic emission control method,and designed the hardware emission circuit of the ground-airborne electromagnetic emission system to meet the emission requirements of high-resolution ground-airborne electromagnetic detection.