hfss patch antenna design problem

Hello, I am new to hfss and i am designing a aperture coupled patch antenna and i am not able to get the results given in the paper.All the dimensions are exactly same as given in the paper except port.So can you suggest what could be the problem in designing port?

Used driven terminal solution type and wave port for excitation.

Problem I am facing: decrease in bandwidth and change in operating frequency dip.

Hi vineelasri,

This sounds like a convergence issue. What are your convergence criteria? Do you have a seed mesh?

It could also be the port - what dimensions are you using? Is it a microstrip line?

Since it is given ansys hfss has automatic meshing i haven't specified anything about meshing.
Parameters i have used:
Port - 2.22*2.016
Length and width of substrate - 20*20
Height of substrate - 0.508
Length and width of slot - 0.2*5.6
Radius and height of patch - 2.17*0.2
Length and width of feedline - 11*0.37
Patch permittivity value - 82

Yes, the feedline i am using is microstrip line.

Convergence criteria: 28ghz with return loss of -30db but we are getting 33ghz with -21db

Hi vineelasri,

Based on that information it seems that your port is adequately sized. Assuming its in the correct location as well, it does seem like this is a mesh/convergence issue. The default adaptive meshing in HFSS is not particularly adequate unless you want to do alot more passes than you need to.

I would set up a seed mesh on the ports and everywhere that you don't have metal. Set the maximum length to half of the smallest feature size (e.g. assign a mesh operation in the slot with a maximum length of half the slot width).

Convergence criteria is measured by your simulation setup, specifically in terms of the S-Parameters seen by the port. Make sure you're doing an appropriate number of adaptive passes, and set the convergence criteria to delta S <= 0.01 (-40dB).

I have tried meshing(skin depth) as you have told.

I am getting a warning:

Seed refinement mesh growth has stalled.It could happen if all the bodies/faces selected for refinement fall outside the solved volume.

I have done meshing to substarate and patch.

There are no noticable changes in the results after the execution maybe due to the warning.Can you please help with this.

Hi vineelasri,

I wouldn't mesh inside conductors - this is probably overkill even for the upper microwave domain. The "solve inside" option should be off be default for conductors. Meshing the substrate and around the patch should be sufficient.

I'm guessing this is why your mesh process is stalling.