Waveguides for Microwave Integrated Circuits

A new integrated fabrication process for microwave circuits is presented basing on waveguides as transmission lines. On principle they are dielectric filled waveguides of about semicircular cross-section. They are manufactured by warming up a thermo-plastic dielectric rectangular strip on a metal plate until it begins to flow and assumes the desired cross-section. Then the strip on the plate is evaporated with a metal layer, the thickness of which is enlarged by electroforming. When compared to other new MIC types the main advantages are the absent radiation loss in bends, space saving design possibilities at acceptable waveguide attenuation. A directional coupler made in this new technology shows the feasibility of the proposed process. Results of measurements near 40 GHz are shown.