Preliminary study on phased controlled electromagnetic method
Electromagnetic wave has both dynamic(amplitude)and kinematic(phase)properties.There were 3 main limitations in the excitation source research of Controlled Source Electromagnetic(CSEM),(1)Single source was widely used,and there was weak and zero zones,was unable to measure.(2)When used dual-source or multi-source excitation,only the dynamic property was used,by change the angle between the sources,achieve signal enhancement in some directions,but weak and zero zone still exists.(3)When the dual-source or multi-source excitation in-phase,the electromagnetic field was simply superposed,and it cannot meet the needs of omnidirectional measurement.In practical,there was no mater single source or multi-source,the measurement angle range cannot be expanded,and the measurement area cannot be extended.These problems could be solved by the following methods,(1)Change the angle between the sources,and change the sources current phase,make full use of kinematic and dynamic properties of the electromagnetic wave,eliminate the weak signal area,make electromagnetic wave distribution in wide-azimuth,or to achieve the electromagnetic wave in a certain direction superposition,improve the signal-to-noise ratio.(2)Make full understanding to the characteristics of electromagnetic field pattern,comprehensive utilization the mainlobe direction,half-power angle and amplitude change,established the wide-azimuth measurement system with dual-source,achieve omnidirectional measurement.Phase controlled electromagnetic method can realize wide-azimuth measurement,improve the exploration efficiency and reduce the exploration cost.
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