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Eliz

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  1. Great! Thanks for the clarification!
  2. Good afternoon! I was wondering whether there was some way to terminate a FEM modal port in a load matching the characteristic impedance?
  3. Eliz

    Error 37389: DGFM

    Excellent! Thank you for this information!
  4. Eliz

    Error 37389: DGFM

    Good morning Mel Thank you for the reply and all the advice!
  5. Eliz

    Error 37389: DGFM

    Good afternoon In addition to my previous question about processes, I ran the Viv_FEM_air_SEP_edge_2el_sp_v1 with MLFMM. I did not get any errors and the results correspond well to the measured results, but the .out file stated that a total of 35 GByte was required in the end, but you mentioned 14 Gb (which is significantly less). I have attached the model and the .out file. I would ideally like to determine the S-parameters of a four or nine element array of dual-polarized Vivaldi elements. Which is why the memory requirements are so important to me (I have a computer with 128 Gb memory and 16 cores to my disposal). Viv_FEM_air_SEP_edge_2el_sp_v5.cfx Viv_FEM_air_SEP_edge_2el_sp_v5.fek Viv_FEM_air_SEP_edge_2el_sp_v5.out
  6. Eliz

    Error 37389: DGFM

    Good afternoon Mel Thank you very much for your advice. I will investigate it. I have a question about the number of processes you mentioned though - I have always assumed that the more processes the better. For example, if I run a model with 12 processes or 6 processes, the former will run faster? Was I incorrect to assume this? Or how does the number of processes relate to memory and speed of the solution?
  7. Eliz

    Error 37389: DGFM

    Good morning Mel I have attached the pfs file. Thank you. *Edit: I have included version 42 in the pfs as well - v42 is just v26 but with first order FEM. To illustrate the great difference in results. Sparam_comparison_26vs37vs42.pfs
  8. Eliz

    Error 37389: DGFM

    Good morning Mel! Thank you for all your help so far. When I used the first order FEM, the simulation results varied quite a bit from the measure results, so I ended up switching on double precision, that also helped. However, I tested this with a single Vivaldi. When I return to 2 antennas to form a dual-polarized vivaldi, I am once again facing convergence errors. I would like to avoid the first order if possible, since it is less accurate and does not agree well with the measured S-parameters. Which is why I now want to decrease the number of mesh elements, to see whether I can still have an accurate simulation without the convergence issues. Which leads to my meshing and the SEP edge port with the FEM model ( please see file attached). Viv_FEM_air_SEP_edge_V26 has an accurate result in comparison with the manufactured antenna's S-parameters, however, when I try and decrease the meshing in any way (as in Viv_FEM_air_SEP_edge_V37 for example increasing the growth rate), a spike randomly appears around 4.125 GHz in my S-parameter results. So now I am wondering whether I am doing something wrong with my meshing? Or whether there is an alternative approach that will avoid this spike from appearing while using less mesh elements? Or even better, whether I can in some away avoid the convergence error (see Viv_FEM_air_SEP_edge_2el_sp_v1) but still obtain accurate results (therefore avoiding first order)? Your help will be much appreciated. Eliz Viv_FEM_air_SEP_edge_2el_sp_v1.cfx Viv_FEM_air_SEP_edge_2el_sp_v1.fek Viv_FEM_air_SEP_edge_v26.cfx Viv_FEM_air_SEP_edge_v26.fek Viv_FEM_air_SEP_edge_v37.cfx Viv_FEM_air_SEP_edge_v37.fek
  9. Eliz

    Error 37389: DGFM

    Good afternoon Mel I have tried to obtain the S-parameters for a single Vivaldi antenna over 2-6 GHz (which is the main range I am looking at). I have two questions: 1. Whenever I simulate the antenna and try the FEM on a region, I get warnings and or errors - all of these warnings and or errors deal with the convergence of the solution. I have noticed that the warnings or errors tend to happen when higher frequencies (above 5GHz) are being processed. Some of the errors and warnings I have received are: ' WARNING 830: Maximum number of iterations reached without convergence, using in the following the solution with the smallest residuum'; ' ERROR 33498: Maximum number of iterations reached without convergence'; ' NOTE 4973: Iterative solution of the system of linear equations not sufficiently converged at the stopping residuum, continuing with the iterations'; ' ERROR 4673: Iterative solution of the system of linear equations failed, maybe try another preconditioner (solution settings)'; ' WARNING 36002: No convergence achieved during the iterative solution (residuum diverges, larger than maximum value)'. I have attached three of my attempts for which I have all received one or more of the beforementioned errors, notes or warnings. I think I might have to change the preconditioner, but am not sure what that does and what the best choice would be, or maybe change the mesh? In one of my experiments, I increased the size of my airbox around my antenna and some of the warnings went away (when I simulated from 2-4GHz), but the warnings returned when I tried to obtain the parameters for 2-6 GHz. Any advice would be appreciated. 2. You mentioned that the modal port has to be 'very large'. I know in CST the waveguide port should be between 5-10 times the thickness of the dielectric wider on each side and higher than the dielectric. Is this rule applicable in FEKO as well? How do I know it is large enough? Thank you for all your help thus far! It is very much appreciated! Viv_FEM_air_SEP_edge_v3.cfx Viv_FEM_air_SEP_edge_v4.cfx Viv_FEM_air_line_v1.cfx
  10. Eliz

    Error 37389: DGFM

    Good morning Mel I found my error in Viv_2el_sparam_v5 - the SEP region around the edge port was supposed to be free space and not air. However, the S-parameter results between the 3 different methods differ considerably. I would've thought Viv_2el_sparam_v2 (without FEM, with SEP) would be more similar to Viv_2el_sparam_v5 (with FEM, except for small SEP box around edge port)? How do I know which ones are more correct? Should I maybe apply local meshing to the edge port in V5? Please see attacehed the V5 output file with S-parameters at 3 GHz. Viv_2el_sparam_v5.fek Viv_2el_sparam_v5.cfx
  11. Eliz

    Error 37389: DGFM

    Good morning Mel I read about the accuracy of the FEM line port in the user manual. Under current sources it says "Note: An intrinsic limitation of the impressed current source is that no radius is considered. The field is singular in the vicinity of the filament affecting the accuracy of the computed input impedance of the source." I managed to simulate the s-parameter of a 2 element finite array with MLFMM (I ran the simulation before you mentioned that MLFMM might not be useful if you have a fine surface mesh) (this is Viv_2el_sparam_v2) and I simulated the s-parameters with FEM (please see attached - Viv_2el_sparam_v4) and the S-parameters differed quite a bit. I also tried your method with the SEP surrounding an edge port, but I got an error message that stated: 'Same solution method must be applied to all dielectric regions in the model', which I find confusing (this is Viv_2el_sparam_v5)? Do you perhaps know why I would get this error message? Viv_2el_sparam_v2.fek Viv_2el_sparam_v2.cfx Viv_2el_sparam_v4.fek Viv_2el_sparam_v4.cfx Viv_2el_sparam_v5.cfx
  12. Eliz

    Error 37389: DGFM

    Good afternoon I tried switching off the DGFM and switch on the MLFMM solver and then tried to obtain the S-parameters. However, after a while it failed as well with 'Error 36772: Not enough memory available for dynamic allocation'. I have attached the cfx model file as well as the out file. I would appreciate any advice. Viv_2el_sparam_v2.out Viv_2el_sparam_v2.cfx
  13. Eliz

    Error 37389: DGFM

    Good afternoon Thank you for all your advice! My simulations are so much faster and use a lot less memory! I wanted to obtain the S-parameters for this array, but got an error that stated 'Error 37374: S-parameter calculation currently not allowed for DGFM'. Obviously if I switch off DGFM, it will once again take quite long and use a lot of memory and the FEM line port is not as accurate as the edge ports for S-parameter calculations. Do you perhaps have any advice on how to efficiently obtain the S-parameters for this array? Also, when using a finite array, how do you specify that you want the S-parameters for the other element's ports as well - it only give an option for port 1 and port 2?
  14. Eliz

    Error 37389: DGFM

    Good afternoon. I have several questions regarding the FEM implementation. I was able to follow the video's instructions for a single antenna element (just to check) and got similar results to when I used other methods - and it is so much faster - thank you! I do have some questions: 1. If I want to use FEM for a two element array - do I have to place the air dielectric around both of them together (in other words they wont each have their own air dielectric box, but share one)? 2. Will this method take mutual coupling into account? Furthermore, after some consideration I wondered whether I could simulate the Vivaldi without the feed line, thereby eliminating much of the fine mesh required to mesh the feed line. In other words, could I feed the Vivaldi with a modal port at the end of the taper (as with the waveguide port in CST) or could I feed the Vivaldi with a line port spanning the start of the taper. I attempted the former in the attached file called Viv_pol_test2_3_FEM_v2 and the latter in Viv_pol_test2_3_FEM_v3. However, I got errors for both cases. For the modal port I received and error that stated 'A modal port must include dielectric areas in order to support wave tranmission' - which I thought I was doing, since it is on a face of the dielectric region. For the line port I received 'Error 19088: Geometry port: Portx - The edge Feedx.Wire2595 must be on the boundary of a dielectric or embedded in a dielectric region' (screenshot attached). Which once, again I thought I was doing anyway? I would appreciate any advice! Viv_pol_test2_3_FEM_v2.cfx Viv_pol_test2_3_FEM_v3.cfx
  15. Eliz

    Error 37389: DGFM

    Thank you so much for you help! I will investigate your solution and come back to you. I tried using a FEM once before, but granted, I still used some form of an edge port, but got an error saying FEM cannot be used with finite arrays? Won't this be a problem?
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