Resonance of a slot antenna made from an aluminum plate (UHF band)

Hello,

I've been searching for some days now and tried some experiment myself.

As the title says, my problem is to check the intrisic resonance of a single slot in a metal layer :


I know that slot is the dual of the dipole (from Babinet principle). That they have same pattern with different E/H direction but different impedance.

A half-wave slot should then resone at the same frequency than a half wave dipole.
Meaning that for a 915MHz we need a 16,4cm slot.
And for 860MHz a 17,4cm.

Is there a (simple?) way to check that my slot has the resonance i want?

What i did:
-Simulate the slot on HFSS to take into account slot width (but would like to check if the simulation is accurated with real slot)
-Tried to see the resonance of a slot by using a RFID tag and check the maximum distance reading (but the results don't give clear answer due to coupling)

So if you have any ideas, i would be glad to "hear" them~

Some new materials

I inspired myself with some info from this (very good) website: https://www.antenna-theory.com/antennas/aperture/vivaldi.php
Even if the antenna is different the idea is the same.

So i used a coax, put the core on one side and the shield on the other. I used the VNA to look at the VSWR and also the distance that would match 50ohm.

The thing is that i find a ~4cm to get a closely to 50ohm matching whereas the simulation gives me a ~1,5cm.
In pratictal i also get the maximum distance functionnement by using the slot and a 50ohm matched device placed at ~4cm.

Sounds like my simulation may have gone wrong~ If someone want to take a look i'll post it in the dedicated section.