Broadband Directional Coupler with High Coupling Attenuation

We present a high-power directional coupler for precise amplitude and phase measuring of broadband highfrequency signals. In contrast to conventional directional couplers, a significantly higher attenuation of the coupled forward signal can be achieved with the same high directivity. This results from a new ring coupling structure which corresponds to an almost lossless serial connection of directional couplers. The higher coupling attenuation allows developing directional couplers with strongly reduced losses and thus a smaller design because no heat sink is required. A realization of a micro strip based coupled line coupler with the ring design is shown.