| Semi-airborne transient electromagnetic method is a new exploration method proposed in recent years,which acts as a new exploration method between ground transient electromagnetic method and aeronautical transient electromagnetic method.It combines the advantages of high power emission of ground transient electromagnetic method and high efficiency exploration of aeronautical transient electromagnetic method,which is mainly used to explore mineral in complex terrain,such as desert and mountain area,that can effectively reduce the risk of exploration,reduce personnel costs and improve the efficiency of exploration.The semi-airborne transient electromagnetic detection system mainly consists of three main parts: the transmitting system,the receiving system and the later software processing system.This paper mainly studies the signal receiving technology of the semi-airborne transient electromagnetic receiving system.This article is based on the public interest project of Ministry of land and resources "Research on semi airborne transient electromagnetic exploration technology based on UAV"(item number: 201311037),it firstly studies the research status at home and abroad of electromagnetic coil system,sensors and software for real-time data processing.Studies the characteristics of signal and noise of semi-airborne transient electromagnetic;analysis of the system characteristics and important parameters of the coil sensor,and put forward a design scheme of coil sensor,design a low noise preamplifier.The synchronization and over sampling techniques used in the synchronous acquisition device are analyzed,and the design scheme of the synchronous acquisition device is compared.The design of the synchronous acquisition device is realized with the design scheme of FPGA combined with the industrial control machine and the PC machine.The basic data processing methods for semi-airborne transient electromagnetic method are studied,including signal superposition,bipolar synchronous sampling and filtering,FIR filtering and channel extraction.On this basis,real-time data processing software is implemented using C# language.Finally,in order to verify the performance of the system,the receiving system(SATR)composed of three parts of the coil sensor,synchronous acquisition device and real-time data processing software was tested,and the system was tested at the same point on the ground with the V8 system of Phoenix,Canada.The results showed that the noise level of the SATR system was 10 nT/s,which is equivalent to the noise level of the V8 system,and the comparison between the test results of the ground V8 system and the air SATR system proves the effectiveness of the SATR system. |
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