Wan Receiver Of Electromagnetic Instrument Hardware Design And Realization

Wide field electromagnetics, a new geophysical electromagnetic exploration method, is presented by academician He Ji-shan, Central South University, based on CSAMT, and measures a component of the field (electric field component or magnetic field component) to obtain the apparent resistivity in the non-remote area using the accurate electromagnetic fields formulas which are valid for all range. Wide field electromagnetic system is a new electromagnetic exploration equipment with great depth exploration, high efficiency, precision and adaptability, based on wide field electromagnetic method and the pseudo-random multi-frequency signal to overcome the defects of the current CSAMT electromagnetic instrument about frequency conversion mode, weak signal caused by remote area measurement,measuring two orthogonal components of electromagnetism.It can use a transmitter to transmit the signal and many receivers receive it at the same time to achieve three-dimensional electromagnetic explorationIn this paper, basic theory and characteristics of wide field electromagnetic methods, system structure of the wide field electromagnetic system and receiver is briefly introduced. It has a detailed analysis of effective electromagnetic signals characteristics and noise acquired by receivers, focuses on the precision low-noise analog circuit design to meet the characteristics of wide field electromagnetic signals and acquisition mode, including the impedance transformation, high and low pass signal filtering, notch filter, low-noise amplifier etc, giving a detailed design with high precision and low noise from the circuit structure and device selection. In addition, the different bandwidth needs the different acquisition time and overlapping period in Wide field electromagnetic system which also requires high precision and high stability signals. We have designed signal acquisition circuit based on high-resolution, high-speed,∑-△analog-to-digital converter AD7762, and also have given the interface circuit with DSP and the related program. At last, the interior indicators test in detail and the field test at Daqing and other places of the wide field electromagnetic receivers are carried out.The noise and consistency indoor test, and the consistency, stability field test all have achieved good results. The receivers can work reliably, acquire credible data, meet the requirements of the wide field electromagnetic method, can be used for field exploration.The paper has won the support and funding of National natural science foundation project, the basis research of wide field electromagnetic system (40827002).