Impedance of patch antenna in HFSS

Hi,

I would like simulate a array of patch antenna on Epoxy. So, I begin by a single patch antenna for determinig the impedance's antenna, before begining the array.

I'm currently simulate the single antenna with HFSS, I use The probe feed patch antenna, I use a wave port 50 Ω, and I move the port along the vertical axe for determining the impedance for each port position.

The problem is that when I move the port, I obtain always ≈20Ω.
I want to khnow the method for determining a impedance of patch antenna .
I must to use a wave port 50Ω?

Thanks

hi
i cant understood whats u mean for change port but for more information about array patch u can read these books and if u feed is microstrip ,lump port is better
1)Broadband Planar Antennas Zhi Ning Chen and Michael Y. W. Chia chapter 3
2)antenna theory balanis chap 14(microstrip)

on microstrip patch antenna the location of feeding is important it is effect the resonance frequency and s-parameter namely the impedance.while you design the microstrip antenna you should learn theroical part about microstrip antenna.
and you have not use 50 ohms port to feed the antenna but if you want to print antenna and if your impedance is high the feed line will be thin and you cannot print the structure.

What about width and length of your patch? Change its width and see how the impedance changes. Feed location is not only the parameter that should be optimized to get 50 ohm input imp.