A Comparative Study of Two Variants of the Equivalent Sources Method in Scattering Problems

In order to compare the stability and accuracy of two particular variants of the Equivalent Sources Method – one using the "least square minimization" technique (LSM) and the other being Ochmann's "full-field equations" method (FFE)–, numerical experiments on a three-dimensional scattering problem have been performed. Results obtained with monopole sets show that, in spite of exhibiting much less stability than FFE and being more affected by the source configuration employed, LSM can provide, under particular conditions, better solutions. It is also shown that, with an expansion in spherical wave functions, FFE and LSM solutions have comparable precision for higher frequencies. At low frequencies the two methods differ, LSM being more precise. Examination of the amplitude and phase of the sources provided by the two methods is used in order to explain their differences in performance. It has been verified that an indicator, based on the LSM source strengths for a given source configuration, can give information concerning which of the two methods is likely to produce a better solution in that case.