Anomalous behavior of near fields calculated by the method of moments

Abstract

The method of moments can be used to find solutions J of the equation X(J) = \lambda R(J) , where R and X are the real and imaginary parts (respectively) of the Z (impedance) operator of a perfectly conducting body. These solutions, called the characteristic currents, are characterized by an important near-field feature-the resulting free-space electric fields tangential to the body are constant in phase over the entire body. Although the method of moments is often used to solve electromagnetic problems where the far radiation fields of the solution currents are of interest, general moment-method theory indicates that the technique should also yield current solutions exhibiting accurate near-field behavior as the dimension of the solution space is increased. The near-field phase characteristics of resonant thin-wire characteristic current distribution, as calculated by several familiar moment-methods schemes, are presented. The ensuing discussion reveals several anomalies concerning the near-field behavior of the fields resulting from these currents. These anomalies are then discussed in light of the basic rudiments of the method of moments.