Some limitations of realistic driving sources in moment method calculations

Two means of driving mathematical models are considered which appear to offer greater realism than the simple pulse source. These are the magnetic current annular ring (magnetic frill) source and the current slope discontinuity source. It is shown that the former is conveniently considered as a toroidal transformer. This approach enables the driving electric field to be derived by inspection from the magnetic vector potential produced by the magnetizing current flowing in the transformer primary. It is indicated that, for practical computation, this source is equivalent to the pulse source. The current slope discontinuity source is portrayed as a portion of a biconical capacitor. Examination of both sources leads to the conclusion that for point matching calculations, neither is free of difficulty: implementation necessitates an integration process which tends to remove the configurational details and hence the benefit of realism. For this type of calculation, neither appears to have any clear advantage over the pulse source. >