Oversized Substrate-Integrated Waveguide for High-Power Millimeter-Wave Systems

In this article, the oversized substrate-integrated waveguide (OS-SIW) is proposed, analyzed, and experimentally demonstrated. The physical parameters and the effect of material surface roughness on the attenuation and the SIW power capability lead to the exploitation of wider and thicker waveguides, as an alternative to enhance the power-handling capability (PHC) and reduce the losses. The resulting oversized waveguide is a guide whose width or thickness is greater than that of the SIW, which is sized to support only the TE10 mode in the operating band. An SIW-to-OS-SIW transition has been designed to allow the component characterization in the W-band. The proposed transition allows to propagate only the desired mode TE10 in the OS-SIW and prevent the higher mode propagation. The experimental results of the manufactured prototypes accord well with the simulations in terms of power handling and transmission losses. The proposed OS-SIW line shows lower attenuation (1.5 Np/m) than a standard SIW (3 Np/m) or a microstrip line (about 3.7 Np/m). However, the OS-SIW 5a has achieved an average power of 90 W at 90 GHz. The investigated OS-SIW configuration offers high PHC, low losses, and easy integration into high-power millimeter-wave systems.