Transient Electromagnetic Method of Small Transmitter Loop

摘要

Small Transmitter Loop Transient Magnetic Method (TEM) device refers to a single square transmitter loop with 2m～5m as its side length,which is available to be applied for mountainous areas with steep ups and downs,city streets,residential areas,narrow and squeezed areas as mines and tunnels because of its flexibility and convenience for construction,is wining favors with wide application.In this paper,the approaches for investigating deeper depth by small loop TEM,power pulse compression for high-power small transmitter loop TEM,topographic influence and corrections are discussed.It points out that transient electromagnetic pulse compression is the reason for long time period of capacitor charging and short time period of discharging; while,pulse compression radar is of long transmitting pulse width and short receiving pulse width.As a consequence,the two are essentially distinct to each other with regard to technology.The simulated results applied the Finite Difference Time Domain (FDTD) method show that the observation time decides TEM investigation depth and the length side of transmitter loop solely relates to signal strength; when supplying high power to small transmitter loop,the signal strength obtained is of the same for big transmitter loop for the purpose of deeper depth investigation.Small loop TEM device is less affected by topographic influence,especially when placing the loop along the inclined mountain planes in addition to the comprehensive corrections of geometry and mountain elevation,the influence could even be erased away.