+ Post New Thread
Results 1 to 11 of 11
  1. #1
    Newbie level 5
    Points: 164, Level: 2

    Join Date
    Apr 2013
    Posts
    8
    Helped
    0 / 0
    Points
    164
    Level
    2

    i need help in HFSS, problem with patch antenna simulation results

    Hi everybody,
    i designed a replica of patch antenna in HFSs and am trying to match the simulation results with the network analyzer results from the real antenna. Currently the results i get from HFSS simulation are totally different and are not making any sense, to me at least. lol
    i mean i know it wont be exactly the same but it should be similar. At this point am not bothered about the performance of the antenna i just want to make sure that what i am simulating is actually correct.
    I am really new to HFSS , so am not sure if i am doing something wrong in design or in analyses stage.

    antenna information:
    - frequency range: (800Mhz- 1Ghz).
    - solution frequency: 866Mhz

    *results from network analyzer , from the actual antenna (S11@866Mhz):

    Log Magnitude = 5.27 dB
    VSWR = 3.38
    Impedance @868 MHz = 19.05 + 25.88i







    i have attached the simulation project file as well as a picture of the actual antenna.I hope someone can help me out and tell me what am i missing or doing wrong, and tell me how to fix it :) .

    Thank you


    Attachment 89468Attachment 89469HFSS_sim.rarClick image for larger version. 

Name:	ant.jpg 
Views:	18 
Size:	2.31 MB 
ID:	89471

  2. #2
    Newbie level 5
    Points: 164, Level: 2

    Join Date
    Apr 2013
    Posts
    8
    Helped
    0 / 0
    Points
    164
    Level
    2

    Re: i need help in HFSS, problem with patch antenna simulation results

    please can someone help me .

    thank you



    •   Alt18th April 2013, 05:25

      advertising

        
       

  3. #3
    Junior Member level 1
    Points: 459, Level: 4

    Join Date
    Jul 2011
    Location
    Germany
    Posts
    17
    Helped
    7 / 7
    Points
    459
    Level
    4

    Re: i need help in HFSS, problem with patch antenna simulation results

    I try your simulation and it is not possible, because your waveport isn't on a boundary. Instead of making a coaxial cable with vacuum. i would use a lumped port between the matching and the ground plane. For a first simulation this is accurate enough.


    1 members found this post helpful.

  4. #4
    Newbie level 5
    Points: 164, Level: 2

    Join Date
    Apr 2013
    Posts
    8
    Helped
    0 / 0
    Points
    164
    Level
    2

    Re: i need help in HFSS, problem with patch antenna simulation results

    Thank you for your reply , i was getting worried that no one will reply me .:)

    i did what you have suggested (i have attached the project file ) , is this what u meant ?
    and does the size of the lumped port matter?



    •   Alt19th April 2013, 05:14

      advertising

        
       

  5. #5
    Member level 2
    Points: 992, Level: 7

    Join Date
    Apr 2013
    Location
    Egypt
    Posts
    42
    Helped
    3 / 3
    Points
    992
    Level
    7

    Re: i need help in HFSS, problem with patch antenna simulation results

    hi
    can i ask u what is the best cst studio or hfss ?



    •   Alt19th April 2013, 06:11

      advertising

        
       

  6. #6
    Junior Member level 1
    Points: 459, Level: 4

    Join Date
    Jul 2011
    Location
    Germany
    Posts
    17
    Helped
    7 / 7
    Points
    459
    Level
    4

    Re: i need help in HFSS, problem with patch antenna simulation results

    Yes. the Port looks good. I do a simulation from your project and it works. But you should do some work on it, because your "air" is not very well placed. It should be lambda/4 away from all edges of the antenna. And i don't understand the sheet "Rectangle1". The resonance frequencies in my solution are 820 and 1095 MHz.

    @mohamed.hagag i use both programms. Cst is easer to learn and guide you through the simulation with many things are automatically done. (Mesh, Boundaries, ...) In Hfss you have do many things by yourself. But can do more complex things in the model. Its hard to say what program is better, because when it comes to the simulation results both are good.


    2 members found this post helpful.

  7. #7
    Newbie level 5
    Points: 164, Level: 2

    Join Date
    Apr 2013
    Posts
    8
    Helped
    0 / 0
    Points
    164
    Level
    2

    Re: i need help in HFSS, problem with patch antenna simulation results

    hi ,

    i manged to get similar resonance frequencies . thank you very much :)
    however , like i mentioned earlier this doesn't really match with the network analyzer results . I mean the solution freq i get from the network analyzer is 850Mhz and 950Mhz ,which make sense since this antenna was originally designed for 930MHz .
    So my question is this an accepted error or deviation between the simulation software and the real thing ( i mean there is a lot of non-ideal factors that am sure the simulator wont take in account,hence the different results) , or is there something am still missing in my design which causing this difference?



  8. #8
    Junior Member level 1
    Points: 459, Level: 4

    Join Date
    Jul 2011
    Location
    Germany
    Posts
    17
    Helped
    7 / 7
    Points
    459
    Level
    4

    Re: i need help in HFSS, problem with patch antenna simulation results

    Have you changed the brick "air" so that the structure is in the middle?
    On your photo of the antenna I can see C1 and C2. But in your simulation are only a big brick of PEC on this place!



  9. #9
    Newbie level 5
    Points: 164, Level: 2

    Join Date
    Apr 2013
    Posts
    8
    Helped
    0 / 0
    Points
    164
    Level
    2

    Re: i need help in HFSS, problem with patch antenna simulation results

    yes, i fixed the "air" box , i increased the size and changed the location , as you advised .
    correct in the original design there are two capacitors C1 and C2 (2.2pF each) , so to simulate that i assigned a Lumped RLC to the "Ant_Matching1" (1.1pf, since C1 and C2 are in-series so their total is 1.111pF) , is that wrong??.
    i attached the latest project file if you want to take a look .



  10. #10
    Junior Member level 1
    Points: 459, Level: 4

    Join Date
    Jul 2011
    Location
    Germany
    Posts
    17
    Helped
    7 / 7
    Points
    459
    Level
    4

    Re: i need help in HFSS, problem with patch antenna simulation results

    No! The Air-Box is still wrong. In the negative z-axis it is not present. Ok I see the C-Bounding in the matching-bricks, you can also use simple sheets for that.
    The infinite sphere is also wrong, it shows no good far field (if it is interesting for you), you must sweep over 360° in theta and phi. I think you should do some more work on the basics of hfss and construction of models, They are some tutorials for dipoles on the web, that might be help.



    •   Alt19th April 2013, 13:50

      advertising

        
       

  11. #11
    Junior Member level 3
    Points: 676, Level: 5

    Join Date
    Apr 2013
    Location
    India
    Posts
    28
    Helped
    0 / 0
    Points
    676
    Level
    5

    Re: i need help in HFSS, problem with patch antenna simulation results

    Thank you for the valuable details shared.
    I would like to have some more clarifications in this regard. In the details shared the monopole gain is defined as 5.16dBi (Gain of dipole +3dB or double the gain of dipole) considering an infinite ground plane. How could we define it over a finite ground plane, for example a 32 feet ground plane? Is there any nominal value or any calculation or any standard practice, something like absolute gain of monopole from 30-400 MHz defined in "MIL-DTL-85670C"

    T&R



--[[ ]]--