APPROXIMATE INTEGRAL-OPERATOR METHODS FOR ESTIMATING THE NATURAL FREQUENCIES OF COUPLED OBJECTS

Of central importance to the singularity expansion method (SEM) for an alysis of conducting objects are the frequencies and currents for the natural modes of the object. When there is more than one object in pro ximity, the direct calculation of these quantities becomes difficult, and it is useful to have approximate methods to simplify the computati ons. This paper presents two approximate methods for calculating the n atural frequencies for a group of coupled objects. The first method is a perturbational one, leading to a transcendental equation for the na tural frequencies. It assumes weak coupling between objects so that th e natural mode current distribution is only slightly perturbed from th at existing on an isolated object. The second method is also perturbat ional and further assumes that the Green's function can be approximate d by leading terms of a Taylor series expansion about the natural-mode frequencies of isolated objects, Results are shown for the case of co upled thin wires and compared to more rigorous moment-method solutions as well as experimental results.