Plane-polar near-field to far-field transformation with three kinds of Fourier-Bessel eigenvalue expansions

An accurate way to compute near-field to far-field transformations by expanding the near-field into a Fourier-Bessel series is presented. All previous studies based on Fourier-Bessel expansions make use of a zero boundary eigenvalue condition. The other two boundary conditions (derivative, linear) are also studied and all the three boundary condition expansions are compared from a viewpoint of accuracy and efficiency in both the near-field and the far-field. The influence of the sampling density in the near-field measurement is also investigated