Recently I am reading on microwave waveguides, especially the case a feed waveguide coupling to another waveguide with short end (a cavity) via an aperture. (Collin, "Foundations for Microwave Engineering", Chapter 7.6). I have a question and I will really appreciate if anyone answers it and helps me understand more.
The aperture looks like a shunt susceptance. And at the resonant frequency, input impedance at the aperture (looking toward the cavity) goes infinite if the waveguide is lossless. On the other hand, physically speaking, a lot more energy will be coupled into the cavity at resonance. But the infinite impedance will reflect all power back, which conflicts the maximum power coupling at resonance. How to understand such a "conflict"?
Thanks.