Issue: S21 flat, no resonance, but eigenmode of same geometry is correct
I'm trying to build a 915 MHz combline cavity filter, two cavities, coax tap feeds.
The eigenmode solve of the identical geometry gives modes at 921.85 and 923.58 MHz which are hopefully correct. Driven modal with two wave ports gives S₂₁ flat around −52 dB, no resonance anywhere.
Geometry: cavity radius 20 mm, height 80 mm; post radius 5.5 mm, height 72.8 mm; coax outer radius 1.46 mm, pin radius 0.635 mm, tap at z = 55 mm, pin penetrates into post
What I've checked: ports assigned with integration lines on the annular faces, Perfect E on the air object, pins confirmed to overlap the posts!
