Method of moments with an equivalent Green´s function technique for modelling broadband cavity-coupled microstrip vertical transitions

A method of moment technique is presented to model the frequency response of broadband cavity-coupled microstrip vertical transitions. The technique divides the original problem into two kinds of regions, and then calculates the electromagnetic field distributions in each region by Green´s functions. However, the closed forms of Green´s functions are not always available. For regions without the closed-form Green´s functions, equivalent ones are derived by the finite-element methods. This gives maximum flexibility in the physical structures. Two designs proposed earlier for the broadband cavity-coupled microstrip vertical transitions are selected for the practical applications of this technique. The simulation results are compared with those obtained from other numerical techniques, and the accuracy and validity of this technique is assessed by measured data. Numerical convergence of the equivalent Green´s function technique is examined and computational efficiency and required memory usage are also studied.