Characterization of mode conversion in oversized rectangular waveguide at 26.5–40 GHz

Mode conversion losses are a big concern when an oversize rectangular waveguide is used to minimize ohmic losses. Oversized waveguide components [1] can be used to minimize ohmic losses when a signal must be transported over a large distance. The waveguide devices at both ends are usually in a smaller and connected by suitable transitions to the overmode waveguide. This combination forms a resonant cavity for higher order modes. We examine how the transmission of the fundamental mode is affected by resonances in the higher order modes. We present the design and simulation results of Transition and Bends. Waveguide bends are known to induce coupling between modes. We could not find in literature a comprehensive set of numerical results in a form suitable for practical applications. This motivated us to produce such a set of results, and to analyze practical consequences, including overmode trapping between waveguide transitions. [2] All the components were simulated using the CST microwave studio [3]. First we have designed the transition and simulated in CST environment. Which gives dips in insertion loss due to the spurious overmode. After that the oversized E and H plane bend were designed and simulated to overcome the coupling between the overmodes.