Improvement for the design equations for tapered Microstrip-to-Substrate Integrated Waveguide transitions

This article describes a new design strategy for Microstrip-to-Substrate Integrated Waveguide (SIW) transitions with different geometries. This design strategy focuses in obtaining a good initial point for the length and the width of the transition. Later, these parameters are optimized together in order to calculate a low reflection transition in the desired bandwidth. With this method, different transitions have been designed, in which the impedance variation follows different mathematical expressions, some of them extracted from the classical theory.