Modified Coupling Aperture to Optimize the Power Transfer in a Fabry-Pérot Open-Cavity Resonator

The push for the usage of higher frequencies (> 30 GHz) towards 5G and 6G is posing new challenges on the antenna design. One of the challenges concerns the dielectric materials used to design the antenna on-chip or in-package. The values of the relative permittivity and loss tangent of these dielectric materials are not always known and need to be characterized. A popular system to characterize these dielectric materials is the Fabry-Pérot open-cavity resonator. The accuracy of the measurement with this material characterization system is determined by its Q-factor. One way to improve the Q-factor is to optimize the design of the coupling hole, i.e. iris, between waveguide and open-cavity. This will lead to a trade-off between the maximum amount of energy coupled into the cavity and the minimum amount of energy flowing back into the waveguide. This article proposes a change in the shape of the iris, which has lead to 2.5 times more power coupled into the open-cavity compared to other known modifications.