What should be the PIFA dimensions of the radiation box for HFSS simulation?

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Wycleef

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Hi guys, i want to simulate a 900 Mhz PIFA antenna in HFSS 11, but I don't know what should the dimensions of the radiation box, in order to obtain the S11. can anyone help me?

thanks,

regards, Wycleef.
 

radiation boundary in pifas

I think that i can help you with you issue. My MSc thesis was all about that. Please read the following which is part of my thesis:


Airbox Dimensions and boundary conditions
----------------------------------------
In order to accurately simulate the behaviour of an antenna in HFSS, an airbox has to be chosen to surround the structure. The dimensions of the airbox can have a large effect on the accuracy of the results. The airbox size must not be too small and must be a certain distance away from any radiating object. Ideally an airbox size should be large, but this will increase the number of finite elements in the solution and also increase computation time. A rule of thumb for selecting the size of an airbox is that all boundaries of an airbox must be at least a quarter wavelength away from the antenna structure. In this example the resonant frequency of 1.3GHz has a quarter wavelength of 57.69 mm. An airbox size was chosen to be 60 mm away from the three sides of the radiating patch which are not connected to the feedline. If the ground plane is large then the airbox only needs to be created above the ground plane since most of the radiation takes place above the ground plane. HFSS requires that airbox boundaries be assigned as radiation surfaces in order that no reflected radiation takes place. The airbox surface which coincides with the ground plane is not selected as a radiation surface.


If you have any questions I will try to answer them and if you want more information please let me know. I hope that helps

George
 
pifa ground plane

hi blerman13

you said the dimension of the airbox to be at least quarter of wavlength away from the 3 sides of the patch.

what about the top side of the patch?

also if the patch antenna is probe fed . should you be using this dimension criteria for the 4th side of the patch?


regards
 

ansoft examples airbox



thank you, blerman13. that was a major issue that i've been having for some time. however, i've been having another problem. maybe you can help me. the problem is that i can't simulate, in HFSS 11, a PIFA. i'm having problems with the construction of the sctructure because of the shorting pin's and the probe feed, i. e., i don't understand how to connect the probe feed and the shorting pin's to the patch and ground. i've seen some tutorial with probe feed patch antenna, but with my PIFA, i can't obtain the suposed S11. can you help me? do you have some simulation file or some tutorial about this?

thank you very much, i appreciate you effort to help me.

Added after 4 minutes:

shahid78,

i think it should be 1/4 wavelength in all directions, unless you have a ground plane big enough. in that case, you radiation box should not ''grow'' in that side.

regards,

Wycleef.
 

pifa shorting pin

I guys.

I've tried to simulate a PIFA to work in the 900MHz band (890MHz-960MHz) with central frequency of 925MHz. this design of PIFA was developed in Ansoft Ensemble, but know i want to replicate the results using HFSS v11, but I can't do it. It gives me a ressonant frequency above 1GHz, when it should be around 925MHz. Could you please see my simulation file and tell me what is the problem, please? I know that the airbox of the radiation boundary doesn´t follow the 1/4 wavelenght dimension rule, but it's the only way to get a S11 graphic whit a ressonant frequency in 925MHz. But I know that is wrong. Can you look at the design, and see if there's some problem with the shorting pins or whit the analysis setup....i don't know, something.....thanks.

regards,

Wycleef.
 

impact of airbox in hfss simulations

The solution type was set to 'driven terminal'. I changed the solution type to 'driven modal' and I got the result what you want.

good luck.
 

Re: PIFA in HFSS

taebin1111 said:
The solution type was set to 'driven terminal'. I changed the solution type to 'driven modal' and I got the result what you want.

good luck.
Click to expand...


but what were the dimensions of the air box that you used? The same as I did or something else?

thank you,

Wycleef.
 

PIFA in HFSS

Can anybody explain when use the driven mode and when use driven terminal. Any big difference?
Thanks!
 

PIFA in HFSS

taebin1111 wrote:
The solution type was set to 'driven terminal'. I changed the solution type to 'driven modal' and I got the result what you want.

good luck!

Different from taebin1111, i delete the port inside and build a new wave port on the selected face of the coaxial, the result goes well. The solution type is driven terminal. FYI, i use hfss 11
 

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