The emerging technology of substrate integrated waveguide (SIW), a veritable paradigm, considering migration from metal walls waveguides to the planar technology. . Since the microstrip line is very practical in many configurations, including active components connectivity, the trend is to merge it in the same substrate with SIW, geometrically irreconcilable structures. This requires the development of transitions, junctions and couplings, with high technical quality, and therefore implies performing a good calculation model. These transitions are very important for the matching of impedance and field between the SIW and planar circuits