RF/microwave be like: everything is a waveguide or resonator when the frequency is high enough. Circuit board? Power plane resonance and edge reflections. Coax cables? When you have circular waveguide modes they become useless. Connectors? The plastic supporting "beads" have resonances. In 2011 it was discovered that even the center pins of a 1.85 mm coax plug and socket can resonate at 50 GHz if they're made too perfect with a near-zero gap - exactly what you do for metrological-grade connectors , thus explaining strange errors in national labs from the early 2000s. #electronics