A general calculation technique for the Green´s functions in the mixed potential integral equation formulation of microstrip-slot circuits

A general technique has been developed for the calculation of the Green´s functions appearing as the kernels in the mixed potential integral equation of passive circuits embedded in a multilayered medium. The circuits consist of strip and slot levels. The mixed potential integral equation formulation is used to describe the electromagnetic behavior of mixed strip-slot structures. The kernels of the integral equation are an electric and a magnetic Green´s function. A novel technique for the efficient and accurate calculation of these Green´s functions is considered. Each Green´s function is written as a sum of relevant surface waves, a singular term (if present), space waves (for open substrates), and a remainder part. Circuit results are given for two slot-coupled microstrip patch antennas. The results are compared with data available in the literature.<>