Closed-form spatial electric field Green´s functions of microstrip structures using the fast Hankel transform and the matrix pencil method

Closed-form expressions of spatial electric field Green´s functions of microstrip structures are presented. These expressions are accurate for a radial distance from one hundredth to five wavelengths. Numerical spatial Green´s functions are efficiently calculated by applying fast Hankel transforms (FHT). These numerical functions are then used to obtain the closed-form expressions in terms of a sum of complex exponentials using the matrix pencil method. Numerical results from this method compare well with those obtained by direct numerical integration. Owing to the utilisation of an FHT algorithm to calculate the Sommerfeld-type integral, the present method is very efficient in obtaining the spatial electric field Green´s functions