How to insert coaxial feed to interdigital filter?
I'm trying to replicate the 8-pole interdigital waveguide bandpass filter example from this link https://anilkrpandey.wordpress.com/2017/12/03/designing-waveguide-filters-for-communication-devices/ in FEKO but I'm not getting the correct results and I suspect that it's due to my input and output ports (CADFEKO and POSTFEKO files attached). What I did was add an inner and outer cylinder and remove the top and bottom faces of the outer cylinder and set it to a vacuum dielectric with the cylindrical shell set to a PEC in order to allow the inner rod to make contact with the input and output lines of the filter inside the enclosure. I also cut out a circle on the enclosure, whose radius is equal to that of the outer cylinder, this was done to remove the section of the box that's blocking the coax cable from connecting with the resonators inside the enclosure. My implementation makes sense to me, however my S21 and S11 responses in POSTFEKO don't match those given my the referenced link and I can't see where I'm going wrong.
Answers
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You don't need a dielectric definition if it is meant to be vacuum.
There was a metallic face at the junction of the coax to the enclosure, effectively shorting out the coaxes.
Maybe the intention was to have a dielectric face there, but then the internal coax region would have required a dielectric setting.
If you delete this face and the one at the other coax, it should work.
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Thanks a million I've been stuck on this for a while now.
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