Study of factors affecting induced voltage of TEM

In the paper,the polygonal approximation method are used to improve the spectrum calculation methods in layered media forward calculations of transient electromagnetic method,in which the large quantities of progressive characteristics of Bessel function is used and the integration interval is divided into and domain to calculate the integral respectively so that the defects of the high computational complexity in Bessel function is overcome in conventional spectrum method.The results show that the improved calculating method is simple,and the computational efficiency has been significantly increased.Meanwhile,such studies that the factors affect the induced voltage,as well as a variety of different geo-electric model using this method are intensively made.The results show that the induced voltage increases with the increasing in the magnetic moments of the transmitter and decreases with the height above the ground where the coil is placed.Reflecting of transient electromagnetic in low resistance domain is better than in the high-impedance domain obviously.The results of these theoretical simulations provide a reliable theoretical basis for rational selection and construction design of transient electromagnetic measurement system.