Accuracy of Sources and Near-Zone Fields When Using Potential Integral Equations at Low Frequencies

We consider method-of-moments solutions of the recently developed potential integral equations (PIEs) for low-frequency electromagnetic problems involving perfectly conducting objects. The electric current density, electric charge density, and near-zone fields calculated by using PIEs are investigated at low frequencies, in contrast to those obtained via the conventional electric-field integral equation (EFIE). We show that: 1) the charge density can accurately be found by using EFIE despite the very poor accuracy in the current density; 2) using PIEs instead of EFIE leads to accurate computations of the dominating solenoidal part of the current density, while the vanishingly small irrotational part and the charge density become inaccurate; 3) it is possible to accurately compute the charge density, in addition to the current density, when using PIEs, but at the cost of a solution of an additional integral equation. Numerical examples involving spherical objects are presented to demonstrate the accuracy of sources and near-zone fields when PIEs and EFIE are used.