HFSS and paper antenna design mismatch

[OkTa]

Hi;

I am traying to simulate wireless antenna 2.4Ghz and 5.8Ghz dual band. I work on a paper (in zipfile). I simulated antenna in HFSS with waveport and lumped port, however antenna's S11 parameter did not above -10dB about 2.4Ghz. Also about 5Ghz, according to papper resonance of antenna drop -10dB about 6.15GHz but in my simulation this value bigger than 7Ghz. I tried everything but I did not find any solution to this. Please help me!!

Note 1: My simulation file is above in zip file.
Note 2:In my opinion problem is caused by wave port. Idefine wave port size according to HFSS manual.
View attachment Simulation_and_paper.rar

 

[myazdi83]

hi
1-you should solve problem in Driven Modal not Driven terminal.
2-you should define waveport properly.
3- to obtain accurate results, define microstrip sheet as copper.
4-it is recommended to define the frequency sweep symmetrical around the solution frequency.

 

[OkTa]

I think I define wave port properly but I am not sure I am new in HFSS.For your other advices I will try. But do I define wave port properly?
Note: I defined wave port 10w hight and 6h to 10h width. And I looked port solve only impedance in 2 to 6 Ghz, impedance in 49.1 to 49.9 is it reasonable?

 

[myazdi83]

ok,
First change driven terminal to deriven mode. Then delete your previous waveport and define a new one. You must define a new line from buttom of the rectangular to the top of it. then your new port can be defined.

 

[OkTa]

hi myazdi83

I tried project in driven mode but it did not work I defined integration line properly but it did not work too.

driven mode and driven terminal mode did not look differrent in terms of s11, but they have different port impedance in port only solution. Why am I conduct this antenna in driven not terminal? and why diriven port impedance properly match 50 ohm than terminal mode but results are the same?

 

[myazdi83]

enjoy from it!
any quastion?

 

[OkTa]

hi myazdi83,

I found this result in driven terminal and my design. Problem in article this antenna has a resonant frequency in 2.4 Ghz and my design and your design has not resonana frequency over there.

 

[myazdi83]

hi
your radiation box is too small.
i simulate your structure in CST 2010 and here is s11.

 

[OkTa]

thanks but I do not understand that radiation box is lambda/4 far away from any radiation surface antenna solution freq is 2.4Ghz radiation box lamba/4=37.5mm. So why radiation box is small?
I tried bigger air box (100mm every radiation surface) but results same

 

[myazdi83]

ok
I suggest using CST.

 

[sv1437]

I will also try to simulate in HFSS and let you know the result.

 

[myazdi83]

I am waiting for your results.

 

[OkTa]

I am waiting too

Also I tried to simlate big radiation box (lamda/4 every) radiation surface I found 2.4 Ghz in resonant but for big radiation box ,I expand box alog x axis (Not radiation surface in here) and I used lumped port. HFSS result meet paper's result. However I don't understand why widen length in x axis (any radiation surface in there) cause this result and How I simulate with waveport

 

[OkTa]

hi,

with revision of simulation, I concluded that resonant freq 2.6 Ghz and below -10dB bandwidth shifted 30Mhz according to orginal solution. My problem was air box dimension and I fixed it but ı do not find why does simulation 30 Mhz shift in S11 occur? What is my problem? please help me
Note: I use lumped port for bigger air box
and myazdi3 can you tell me which port you use and what dimension is your air box ?
Note:I added my final simulation below
View attachment Newsimulationandpaper.rar

 

[sweetchoto]

I have solved your problem. i am gonna upload the result soon. I got quite good matching with the results of the paper.

---------- Post added at 00:33 ---------- Previous post was at 00:26 ----------

Hi,
These are the S11 results which i have got from HFSS and they match closely to the ones specified in Paper. Are you looking for these results?

 

[OkTa]

Yes thanks for results but I do not understand my problem is. Which is your air box size and what do you use waveport and dimension? if it possible can you send me a design file?

 

[sweetchoto]

Yes here is the Design file.There was nothing wrong with your Waveport dimensions,they were absolutely fine. The changes i have made you can see in the attached design file. If you have any questions do not hesitate to ask. Enjoy and have fun!!!!

 

[OkTa]

Thanks a lot but I have few question.
1. How do you define waveport in internal of airbox ?
2.Why do you change name Msfeed and T? Do you change any parameter in here?
3.How do you define air box size ? (lambda/4 etc.)
4.I tried to perform simulation with lumped port because wave port didn't define ( and I do not know) in internal structure. And same design but diffrent wave port what do you tihnk my results shifted 300Mhz according to paper in this situation? using lumped port is it bad or good?
5.Why don't you define integral line?

 

[sweetchoto]

1- You can always define Waveport inside the airbox,the only thing you have to do that is to enclose the waveport with a PEC box in order to avoid it from getting shortcircuited. In the attached design file i have given the name 'Waveport_cap' to this PEC box.
2- I have changed the names only so that they become more meaningful,you can give them any name u want and it wont change anything. I do not change any parameter.
3- Airbox size should be Lamda/4 from radiating surface in all direction and be careful to use the lamda calculated on the basis of lowest frequency in the range of your interest.I used 2.3 GHz to calculate Lamda.
4-Even with lumped port you should get the exact results. I didnt try it because i was too lazy to define a newport when you had already defined the Waveport perfectly. So i just used it

I did not see your results. can you just post the S11 plot of your result.

/SC

 

[OkTa]

My lumped port solution in
View attachment Newsimulationandpaper.rar.
In file I do not save output file but for 1.9 - 3Ghz; 2.42 - 2.76 Ghz below -10dB and in resonance freq. -27dB.

Also I have two question;
1.Why do you define integration line on port?
2.I simulete with box instead of rectengular for pec parts and air box in your simulation vacumm I change it to air. So Under this condition only resonance frequency S11 different from paper (-18dB). Why does cause this? I think my assumption is quite well match with real situation.

there is a problem in here but I did not find.
did you put wave port in the middle of pec box? where is it location?
Edit:I understand location of wave port

thanks