A Capacitive SIW Discontinuity for Impedance Matching

We present a shunt capacitive substrate-integrated waveguide (SIW) discontinuity for the first time. The discontinuity is parametrically characterized in terms of its reactive impedance, and an equivalent circuit model is presented and validated. C-band prototypes are manufactured and measured, confirming the simulated results. The utility of the discontinuity is then demonstrated as a part of a matching network for an S-band amplifier. A simple synthesis method for the matching networks is presented, which requires minimal numerical optimization. The amplifier is prototyped and measured and found to be in good agreement with simulation.