The paper provides a review on the Surface Integrated Waveguide approach to microwave and millimeter wave circuits. Although the history of SIWs is comparatively recent, this guiding structure has proven the capability to integrate within a (M)MIC approach a rectangular waveguide, allowing for the development of high Q and low-loss component that cannot be implemented in quasi-TEM transmissive media, like the stripline, the microstrip and coplanar waveguide. During the last few years SIW components and circuits have shown excellent capabilities in microwave and millimeter wave applications, providing low-cost, miniaturized implementations for a variety of passive components, such as filters, directional couplers, resonators, and antenna feeding systems. Micromachining has demonstrated the capabilities of the SIW approach within the framework of monolithic integrated passive components, while SIW implementations in flexible substrates will pave the way to low-cost, consumer electronic products that could not be realized in conventional quasi-TEM transmission lines
