Abstract: The EM field of arbitrary point in an irregular loop can be considered as the sum of the EM field of many circle loops in the irregular loop at the point. Therefore the authors may obtain the EM field of the irregular loop as long as the authors work out the EM field of each of the circle loops. The key to the success of this method is how the circle loop in the irregular loop is divided. The authors make a circle with the center of the circle located at the measuring point so that the irregular loop is divided into two parts, i.e. inside and outside the circle. Then the authors divide the outside of the circle further into many small circles. By doing so, the authors transform the irregular loop EM field solving problem into the circle loop EM field problem.

Key words: irregular loop source, layered medium, TEM field, forward and inversion