Accurate Power Loss Computation of Closely-Spaced Radiating Wire Elements for Mobile Phone MIMO Application

A moment-method formulation was developed using two geometrically-orthogonal basis functions to represent the total non-uniform surface current distribution over a wire radiating element. Extended basis functions were used to reliably treat the discontinuity of the current at the free ends. A surface kernel was used over all of the antenna structure. It was found that the axially-directed component of the current distribution around the surface of the wire was highly non-uniform and that there was also a significant circumferential current flow due to capacitance between parallel wires, both of these being effects that are overlooked by standard filamentary current representations using an extended kernel. The impedance characteristic showed good agreement with the predictions of a standard filamentary-current code, in the case of applied uniform excitation along the local axis of the wire. However, the power loss computations produce significantly different results.