In this paper, an efficient interpolation method is presented in order to compute the Green’s functionassociated to electrical sources, when they are placed inside cylindrical cavities. The interpolation schemeis formulated in the frame of the spatial images technique recently developed. The original idea was tocalculate, for every location of a point electric source, the complex values of the electric dipole andcharge images, placed outside the cavity, to impose the appropriate boundary conditions for thepotentials. In order to considerably reduce the computational cost of the original technique, a simpleinterpolation method is proposed to obtain the complex values of the images for any source location. Todo that, a rectangular spatial subdivision inside the cavity is proposed. Each new sub-region is controlledby means of the exact images values obtained when the source is placed at the four corners of the region.The key idea is to use a bilinear interpolation to obtain the images complex values when the source islocated anywhere inside this sub-region. The interpolated images provide the Green’s functions of thenew source positions fast, and with high accuracy. This new approach can be directly applied to analyzeprinted planar filters. Two examples with CPU time comparisons are provided, showing the highaccuracy and computational gain achieved with the technique just derived.
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