An efficient series expansion for the 2D Green´s function of a microstrip substrate using perfectly matched layers

A new efficient technique is proposed to derive a series representation for the two-dimensional (2-D) Green´s function of a planar substrate. A perfectly matched layer (PML) is used to turn the original open configuration into a closed one. The resulting structure is regarded as a waveguide and the resulting-analytically known-discrete set of eigenmodes is then used to expand the Green´s function. The method turns out to be elegant and efficient for distances larger than 0.1λ away from the source