A comparison of two spherical wave expansion techniques using the circular aperture as an illustrative example

Spherical wave expansion (SWE) techniques are a mature and increasingly popular method for the analysis and measurement of the near- and far-fields of radiating antennas. A SWE technique based on scalar spherical wave mode coefficients (SSWMCs) and vector spherical wave functions (VSWFs) has received considerable attention and has been developed to a mature state. A spherical wave expansion technique based on vector spherical wave mode coefficients (VSWMCs) and scalar spherical wave functions (SSWFs) has been proposed and applied to the problem of radiation from wire antennas. The paper objectively compares the aforementioned SWE techniques, both qualitatively and quantitatively, using the circular aperture as an illustrative example. The need for such a comparison stems from questions posed concerning the relative efficiency, complexity, and general applicability, both from an analytical and computational standpoint, of the two SWE techniques.