An Alternative Plane Wave Decomposition of Electromagnetic Fields Using the Spherical Wave Expansion Technique

In this letter, we expand electromagnetic fields into plane waves by first employing a spherical wave expansion (SWE) and determining the coefficients of the plane wave expansion in terms of spherical wave functions. This allows for a more general and computationally efficient approach compared to the traditional plane wave expansion. Our technique consists of two main parts. First, SWE is used to express any electromagnetic field, which can be specified analytically or by numerical data. The unknown SWE coefficients are obtained using a numerical technique. Then, the spherical vector wave functions are converted into a series of plane waves. Results demonstrate excellent numerical accuracy and efficiency. The method can be applied to both antenna and scattering problems.