Near-Field Analysis by the Vector Wave Expansion Technique and the FFT

The dyadic Green's function expanded in the vector waves (cylindrical or spherical) is used to determine, from source function, the coefficient of expansion of the source fields. The reconstructed field over the surface of any cylinder or sphere surrounding the source is reduced into a two dimensional Fourier transform which is then evaluated using the Fast Fourier Transform (FFT) algorithm. This yields treamendous computational efficiency over the conventional integration of the aperture sources. Furthermore, the present technique, illustrated with rectangular and circular apertures, has wider applications than the recently reported Plane Wave Approach which has comparable computing efficiencies.