Ultra wideband vertical microstrip–microstrip transition

Simple design guidelines for an ultra wideband aperture-coupled vertical microstrip–microstrip transition are presented. The proposed transition uses broadside coupling between elliptical-shaped microstrip patches at the top and bottom layers via an elliptical-shaped slot in the mid-layer. Theoretical analysis indicates that the best performance concerning the insertion loss and the return loss over the maximum possible bandwidth can be achieved when the between the top and bottom coupled patches is equal to 0.8 (or 1.94 dB). Simulated and measured results show that the proposed transition has an insertion loss of <0.7 dB and a return loss of >15 dB across the frequency band 3.1–10.6 GHz.