A low-profile, wideband transition between a coaxial waveguide and a substrate integrated waveguide (SIW) is presented in this paper. The transition is designed for a reconfigurable metamaterial antenna realized in multilayer Printed Circuit Board at X-band. The transition achieves S11 below -15dB across a bandwidth of 19%, making it attractive for many practical applications. Full wave simulation results will be presented along with subtle details of the fabrication such as effects of prepreg layers.