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Hamad

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About Hamad

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  1. Hello there, I am trying to install FEKO 2018.2 on my computer, but when I do so, I cannot find the page associated with typing in the license path which is a server (see the attached photo). I have done this before with the 2017 version, but I do get that option with 2018.2 installation file. I have noticed that note in the attached photo, and I have deleted the old path. Can you explain to me why I do not get that option. FEKO 2017 version cannot be updated either, so that's why I am trying to install 2018 which is the version I am looking for.
  2. Hey Mel, This is the response of the author on the size of the ground plane and feed length: If the ground plane dimensions are fixed, then I would think that the feed length would only change the phase of the reflection coefficient, but not the amplitude (assuming a lossless feed). However, if the ground plane size is changing along with the feed length, then there could well be a change in the reflection coefficient magnitude as well as phase.
  3. Mel, it is not the size of the ground plane that is causing the impedance to change: it is actually the feed length. As a proof, if you go back to my models Example_ap_coupled_DRA and Example_ap_coupled_DRA2 (see above), where the edge port is within the dielectric substrate and hence the feed length does not change as you change the ground plane's size, you will see that there is barely any difference between the two models when you keep the feed's length the same.
  4. Yes, do you keep entering a number that would result in four triangles along the width?
  5. Mel, The quarter-wavelength stub length is fixed, so I thought that's what matters based on my understanding to the theory of transmission line. In respect to the substrate and ground length, yes it is not specified in the book example; however, it is assumed that length is made large enough for the DRA to work. I have tried to place the edge port half way between the bottom and top part of the via and compared to the technique I have used before, and that do make a difference in the result. However, meshing the aperture (do you mean the via) with four triangles across the width of the aperture is something I have not attempted before and I am not sure how it can be done. Can you possibly show me how it is done? Other than that, do you think the model is flawless.
  6. Jif and Mel, Thanks again for taking your time in replying to my inquiry! I have been doing an intensive investigation for months on different DRA examples to make sure I am properly modeling a DRA coupled by an aperture slot feed. In a new example (attached to this reply) taken from "Dielectric Resonator Antenna Handbook" by Aldo Petosa, the width of the feed is definitely lambda_0/30, even at the upper frequency. I have modeled the DRA in the example using both techniques: having the edge port either within the dielectric substrate or at the edge of the substrate with including that free-space region. Here are some observations: 1) Both techniques yield approximately the same input reflection coefficient values; however, they are slightly off from the results found in the book. The dip is at 5.96 GHz whereas it is around 5.7 GHz in results found in the book (for the case when ls=10 mm and s=5mm, page 64) . In addition, the input reflection coefficient found using FEKO models is way off at frequencies off that dip. If you believe that the FEKO models are defined properly, then do you think that the results in the book might not be as accurate as FEKO models? 2) I have noticed as the length of the feed is shortened, there is a change in the input reflection coefficient. This can be observed in the following attached models: Example_ap_coupled_DRA.cfx: the feed line length is 20 mm + stub length of 5 mm (ground plane size 40 mm x 26 mm) Example_ap_coupled_DRA3.cfx: the feed line length is 15 mm + stub length of 5 mm (ground plane size 40 mm x 26 mm) Example_ap_coupled_DRA4.cfx: the feed line length is 12 mm + stub length of 5 mm (ground plane size 40 mm x 26 mm) If you make the feed's length 10 mm, the dip actually vanishes in that frequency range. I have even seen cases in which making the length longer can drastically influence the outcome of the input reflect coefficient. Such thing does not agree with the theory of transmission line, so is there any explanation for this? By the way, the edge port in the above models was placed in the dielectric medium, so the feed's length is varied without changing the size of the ground plane. Your comments are highly appreciated about the issues of discrepancies between the book's result and FEKO models and the effect of the feed's length. Example_ap_coupled_DRA2.cfx is a model where the a larger ground plane is used . Example_ap_coupled_DRA_FreeSpacePort.cfx is a model where the edge port is placed in a free-space medium. All FEKO models are contained in the folder attached. Cheers, Hamad Aldo_Book_Example.pdf Book_Example_v2_NewDesign.zip
  7. Thanks Mel for answering my questions, I am trying to model this while the port is within the dielectric medium; in the model attached Example_ap_coupled_DRA_testingNewVia.cfx can you help me with the error I am getting for the port? Example_ap_coupled_DRA_testingNewVia.cfx
  8. Hi mel, Thanks for taking the time to look at my model. The model was created based on the paper attached in my original post, so I went with whatever feed's width they proposed. Would you mind addressing some of the following questions/comments : Q1) FEKO support told me to connect the two conducting faces which must lie in free space (or homogenous medium), and that's why you see in RDRA_Poylmer_ApertureCoupled_test2.zip the little free space region where the port is created. I was not told anything about the feed width in respect to the edge port. In the other model called Example_ap_coupled_DRA.zip , the port is immersed within the substrate; I used that technique instead based on one of the FEKO models called which "ap_coupled_patch_finite" included in the software's directory. So, I am not sure what the difference is between the two techniques and which one is more accurate? Q2) Is the via (triangular section) connected to the port be lambda/30 or less only, not the edge of the feed? Q3) I have tried to implement your technique based on your attached picture in which I see that you included that triangular section and got rid of the little free-space region for the port. Unfortunately, I get an error that "An edge port may not be defined on the surface of a dielectric body, See also message in the output file" ,even though I do not see that is the case. I am attaching the model where I applied that triangular section; would you please let me what I could done wrong here. RDRA_Poylmer_ApertureCoupled_test3.cfx
  9. Hi JIF, Thanks for having a look at my model and sorry for the delay. I do not get notified when somebody replies to my post. Anyway, I have followed all the steps you have pointed out and still no success. I have also created another model called " Example_ap_coupled_DRA" in which the port is placed within the dielectric medium of the substrate (one of FEKO examples is done like that), but again I am still not even close. The first model "RDRA_Poylmer_ApertureCoupled_test2" is basically the same as the original except that the area under the DRA is replaced with PEC, mesh is refined, and magnetic symmetry is placed. Also, I have found out that when the length of the feed is changed , there is a noticeable change in the input reflection. Can anybody still help with this problem? CheersRDRA_Poylmer_ApertureCoupled_test2.zip Example_ap_coupled_DRA.zip
  10. Hi Wilco, Thank for you reply! Yes, I hope this can be made available in future releases as it may be useful for some. Regards,
  11. Hi there, In FEKO for the CMA, the eigenvalues of the individual modes can be obtained in the output file, but unfortunately I cannot find the eigencurrents (Jn), where [X][Jn]=lambda[R][Jn]. When the current is requested under CMA configuration, only those currents on the triangular elements can be obtained. So, I would need some help in how to obtain the eigencurrents. Thanks
  12. Hi there, I have contacted FEKO support before about modeling a DRA in FEKO and provided their team with the model attached. I got positive feedback, but after I simulated it the model which is available in the literature, I am not getting even close to those measured or simulated results. Can anybody give me some feedback on the model and if there is anything wrong. I am also attaching the paper in which you will find the complete description of the design. Cheers RDRA_Poylmer_ApertureCoupled_test.cfx DEVELOPMENT OF POLYMER-BASED DIELECTRIC RESONATOR ANTENNAS FOR MILLIMETER-WAVE APPLICATIONS.pdf
  13. The following script will do: Union1 = project.Geometry["Union1"] for key,value in pairs(Union1.Regions) do value.Medium = dielectric end This works and if you have any comment let me know.
  14. Hi there, I have a question about using lua script to assign a dielectric medium to an imported geometry in lua script. The imported geometry consists of three adjacent pieces which are unionized in the script (see the attached file). I am trying to create assign the defined dielectric medium to all those unionized geometry (the three pieces) all at once, so can anyone help me with that? I was successfully assigning the medium to the individual pieces (see the attached script), but I need a script that do the assignment to all the pieces in the union all at once (just like how I perform the union). Test1.lua (attached script) includes the command to import the geometry in test1.dxf which contains the three pieces. test1.lua
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