Patch Antenna in HFSS

Hi every body,

I'm currently simulate a simple patch antenna in HFSS, and I don't know exactly the dimensions of the air box (Radiation boundary). You think that λ/4 is suffisant?

Thanks

Hi, you need to follow the following guideline
- Place at least λ/4 from strongly radiating structure
- Place at least λ/10 from weakly radiating structure
Good Luck with your work

Thank for your reply,

But for the weakly radiating antenna, I must to use λ/10 if I work in Near field, but I'm in the far field.

Hi,

No,for weakly radiating structure Lamda/10 is still in far field not near field. For patch antenna you should stick with Lamda/4 condition and yes it is sufficient.

/SC

Hi, λ/10 is minimum so no need to exceed this value but yes you can make more far away but that will just waste your computing resources. Yes the same applies to far field, that what the rule book says:)
I agree with Sweetchoto.

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I'm not agree, we can have a weakly radiating antenna at 1GHz for example, and in this case the near field is not applied from λ/10. The boundary of the near or far field depends of the frequency.

You are wrong. It depends only on the radiating structure strength. If you have a strong radiating structure stick with LAmda/4 condition,otherwise with Lamda/10.
Read HFSS help to correct yourself!!!!

Ok.

I study a patch antenna at 800MHz, so the dimension' s 20*11cm with the feed line.
So, in the first time, I used a air box more than λ/4 for a patch antenna (800MHz), the resonant frequency is 800MHz with a good S11, and when I increase the dimensions air box the resonant frequency is different of 800MHz.

How can I know the good dimensions for obtaining the true result.

Thanks

hi
is lower frequency or small dimension the hfss result not reliable so for this condition i advise to convert u HFSS file to .sm3 file and and simulated u antenna in CST to achieve a reliable answer
but for simulation in hfss if the D is diameter of antenna i suggest u the chose u air box around 2D at less than 1 GHz application

Astonishing because I have seen dozens of structures using HFSS and no one complained ever about size limits.

hi
if u upload u patch may be we can help u more with out antenna i have no idea about u antenna and in papers many time u see result that is wrong

For a Simple patch antenna (if it is not strong radiator) ---lambda/8 or 10 size of the air box is sufficient .. if ur not sure if it a strong radiator or a weak radiator.. i would say increase ur air box till the point ur resonant freq doesn't change significantly....

DO you any proof to back your claim ??? HFSS is absolutely fine for lower frequencies and smaller dimensions aswell. HFSS always gives more accurate results than CST you are suggesting to use.

hi sweetchoto
i am not agree with u idea about CST i usually design my antenna in HFSS and then check it with CST and then experimental it and the CST result same as experimental and lower frequency and small dimension when u cant define u antenna radiation box i advise u first check it with CST time domain simulation

---------- Post added at 08:58 ---------- Previous post was at 07:52 ----------

hi
another way for understanding that if your radiation box enough for u antenna is u seeing the antenna pattern in hfss
if u antenna gain minus or pattern deformed and your structure is an structure of antenna then u can find u radiation box is good or not

I use CST and HFSS. The difference between the two softwares is that CST use two method of simulation: Time and frequency domain analysis, but HFSS use only the frequency domain analysis.
So, the choice of software depends on the choice of antenna structure.