Global vs. bandlimited basis functions in the analysis of axisymmetric reflector antennas

An available strategy to extend the moment-method (MM) technique to electrically large, smooth objects is to use global (entire-domain) basis functions. They were previously employed in the analysis of large, axially symmetric reflectors. It was shown that an average of 2-3 basis functions per wavelength (spatial-sample count) was sufficient for a convergent solution. This number contrasts with a minimum of 6-10 in the case of local functions. Apart from this advantage, global representations suffer from a major drawback: the impedance matrix filling time grows with D/sup 4/ in contrast with D/sup 2/ dependence for local (sub-domain) functions, where D is the length of the generating arc. In this work, a ´quasi-local´ bandlimited set of basis functions introduced by Hermann (1990) is successfully adapted to analyze the scattering from axially symmetric reflector antennas. Besides requiring almost the same number of expansion terms as global functions, these functions permit a matrix fill time with a D/sup 2/ dependence.