Generalized multipole technique without redundant multipoles

Automatic multipoles placement in the Generalized Multipole Technique (GMT) generates also multipoles that are not necessary for obtaining accurate solutions and may prevent numerical stability. It is therefore important to find out these multipoles and to eliminate them. Two procedures for identifying the redundant multipoles are proposed by using either the singular value decomposition or the rank revealing QR decomposition. Simulation results for both cases show significant improvement in numerical stability as a result of removing the redundant multipoles. A comparison between the two methods is presented for the example of a horn antenna with a radiating elliptical aperture.