Research On The Three-component Transient Electromagnetic Receiving System Based On ZYNQ

TEM has the advantages of obvious abnormal response,strong resolution,high construction efficiency and large detection depth,etc.It has been widely used in the fields of ore body detection,underground space detection,geological structure sounding and Marine earth detection.The horizontal component of the transient electromagnetic signal contains rich geological information,and the observation of the three-component transient electromagnetic signal can better explain the abnormal body's trend,inclination and inclination.The magnetic field intensity signal in the late stage of transient electromagnetic secondary field is strong and stable.For this reason,this paper has carried out the following research work on the three-component transient electromagnetic receiving system:Firstly,the detection principle of coil sensor and fluxgate sensor is analyzed,and then the advantages of their combined detection are analyzed.Based on the investigation of the transient electromagnetic receiving system at home and abroad,the demand analysis and function design of the three-component transient electromagnetic receiving system are carried out,and the overall design scheme of the three-component transient electromagnetic receiving system is proposed by comparing the four technical schemes and selecting ZYNQ-7020 embedded processing platform.Then,the key parameters affecting the sensitivity of the induction coil,such as winding number and diameter,are analyzed,and the three-component induction coil is wound according to the design parameters.This paper analyzes the application requirements and technical indexes of three-axis fluxgate sensor in TEM,and selects Mag639 accordingly.Secondly,the induction signal of the electromagnetic sensor needs to be adjusted before it is transmitted to the receiver.According to the characteristics of the transient electromagnetic signal,a fourth-order butterworth low-pass filter with a cut-off frequency of 15.3k Hz is designed by simulation.According to the detection requirements of TEM,programmable amplifying circuits with amplification multiples of 1/8,1/4,1/2,1,2,4,8 and 16 times are designed,and an 8-channel A/D conversion chip ADS1278 with A conversion rate of 24 bit and 144 ksps and reference source REF5025 are selected to design the A/D conversion circuit.In the field work of the receiver,the battery is used for power supply,and the system power supply is designed by combining the dc-dc switching power supply with the LDO low voltage difference linear stabilized power supply.Transceiver synchronization is the key technology of TEM.Four synchronization methods are compared.GPS synchronization method is adopted and the GPS module of NEO-M8 N with PPS accuracy of 60 ns is selected as the synchronization signal source to ensure the accuracy of transceiver synchronization.Based on embedded Linux,a driver for parameter transfer,data transmission and a data storage software for storing transient electromagnetic data and GPS information are designed.Based on the cross-platform feature of Qt,the man-machine interaction interface is designed.Finally,the design of the three-component transient electromagnetic receiver system performance test indoor and field single-point detection data contrast,fengfeng value of 23.19?V receiver noise,system linearity was 0.1424%,the system error was 0.699%,the channel crosstalk rejection ratio of 92.4977 d B,under the condition of same launch,flux-gate later than secondary field of magnetic field strength reception coil sensor receives the decay rate into the secondary field noise area.The results show that the system basically meets the design requirements,and the combined detection of fluxgate and coil sensor can provide more deep information.