i have designed a Pifa antenna in CST but why its not working ，， Feeding problem ?

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Hello guys
i have designed a Pifa that works in 900 MHz and i got this shape

PIFA.rar
i think the problem is in the Feed please if u have any information hot to improve the efficiency of the S Paramater
i need it to decrease to a minimum on 900 MHz

Can anyone help me if u think i have other problems please :D
Best regards
Rio

Hi Rio,
From my brief experience with PIFAs I noticed your lack of a ground plane and your short isn't coupled with one. Also if your going to use a coaxial type feed probe I suggest modelling that too with the use of a wave port. That said, I have modified your design with my suggestions (Find attached) ; although some further tweaks might be needed.

Why not just use the free (evaluation version) of Antenna Magus to design your PIFA?