Rigorous method for calculating Gap waveguides impedance using transmission line theory

Since the Gap technology waveguides were presented some years ago by Prof. Kildal, many contributions have shown the potential advantages of these waveguides for the implementation of high-frequency microwave circuits. In these structures metal contact is not necessary and dielectric losses are avoided. However, the presence of periodic elements implies a difficult characterization of the waveguide under study, which entails some uncertainty of important waveguide parameters such as the propagation constant or, specially, the impedance. In previous works, the impedance was calculated through the computed fields inside the structure. In this work it is presented a method based on a transmission line approach, which allows to calculate the impedance and the propagation constant treating the waveguide under study as a circuital element. This approach seems to be more adequate as a previous step to circuit design.