井中电磁波CT场源的时域特性分析

设计了一种ＬＲＣ电路控制的瞬变垂直磁偶极子场源，该场源可通过线路中的电阻Ｒ调节其振荡频率和衰减速率，以获取高能量、穿透能力强的时域电磁波信号。理论分析表明接收波形随距离衰减的程度远大于随电阻率减小而衰减的程度；当观测距离大到一定程度或电阻率小到一定值时，记录的时域波形近似为源信号的包络线，这样就相对简单且易于测量其峰值旅行时，从而达到高分辨率成像的目的。

ANALYSIS OF CHARACTER IN TIME DOMAIN OF ELECTROMAGNETIC CT SOURCE

The character of electromagnetic source has a heavy impact on the resolution,penetrating depth and quality of CT. Authors of this paper has designed a LRC circuit as the vertical magnetic dipole source in time domain. The oscillation frequency and decreasing rate of amplitude of source is adjustable by increasing or lowering the resistance in the circuit so that a time domain electromagnetic signal with high energy and powerful penetration can be achieved, Theoretical analysis indicates that the damping degree of wave due to the distance between transmitter and receiver is far greater than that due to the variation of resistivity in which the source embedded, and when the transmitter--receiver distance is greater enough or the resistivity is smaller enough that the shape of wave has become very simple. Under the circumstances the travel time is easy to be measured and results of high quality will be acquired.