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Bidisha Barman

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    Computational Electromagnetics
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  1. I am trying to simulate a 4x4 array of microstrip patch antennas. First, the simulation was done on an infinite ground plane which resulted in 15.65 dBi of boresight gain. However, on replacing the infinite ground plane with a finite one (and solving the model with MLFMM solver to reduce computation time), the radiation pattern undergoes complete degradation with no mainlobe whatsoever. Why is this happening? The same model has been simulated using other commercially available EM solvers on finite ground planes, and the results obtained are as expected. I am attaching a figure that compares the radiation pattern, of the 4x4 array on finite ground plane in the YZ-plane (phi = 90 deg plane), obtained via different EM solvers. The .cfx files for the 4x4 array are also attached. Thank you in advance. 4by4_InfiniteGnd.cfx 4by4_FiniteGnd.cfx
  2. Hello, I have designed a coaxial probe fed microstrip patch antenna and have excited it with a trapezoidal input pulse (using the "New Time Signal" tab in POSTFEKO). I want to obtain the output signal at a certain distance from the antenna. How can I do that? Thank you in advance.
  3. Is the 100 GB the RAM requirement? Or is it the hard drive size you need to save your data?
  4. Thank you so much Mel. Can you let me know the memory specifications of the computer which was used to run the program?
  5. Hello, I have designed a simple probe fed microstrip patch antenna in FEKO, which produces a 43.1% 2:1 VSWR bandwidth (638.2-990.6 MHz). The .cfx file for the antenna is attached. This antenna is now used as each element in a uniformly excited 11x11 array on a finite circular ground plane. The array was simulated (using supercomputer) to calculate the radiation pattern at 3 different frequencies (638.2, 814.4, and 990.6 MHz). Results could be obtained at the two lower frequencies of 638.2 MHz and 814.4 MHz, but it returned an empty matrix for 990.6 MHz. Why is this so? What can be done to resolve this issue? Thanks in advance. 5lambda_638.2MHz.cfx 5lambda_814.4MHz.cfx 5lambda_990.6MHz.cfx 800MHZ_TMM10i.cfx
  6. So, will this MLFMM solver work if I take a bigger array (in that way, I am increasing the dimension to several wavelengths in both directions)? I have already simulated a 10x10 array using the standard MoM solver. So, I want to see the efficiency of other solvers now. What other solvers can I use to obtain the array radiation pattern?
  7. Thank you Mel. I tried using finite ground plane. This time I took a 4 element linear array. But I am still getting some error message. I have attached the .cfx file here. Can you please go through this and suggest the corrections to my model? 3by3ArrayOfAntenna1.cfx
  8. Hello, I have modeled a 10x10 array of microstrip patch antennas. I want to use the MLFMM solver to check the radiation pattern of this array. In order to do that, I first selected the "Solve Model with multilevel fast multipole method (MLFMM)" option under the MLFMM/ACA tab of the Solver Setting. This resulted in error 37356, which says that DGFM and MLFMM cannot be used together. Therefore, I disabled the DGFM solver and then checked the MLFMM solver only. Now I am getting error 2580, which says that "No special Green's function may be activated with the MLFMM". Where am I going wrong? Please let me know the correct way to use this solver. Thanks in advance.
  9. Hello, I am simulating a linear array of 25 dipoles with all the elements placed along the X-axis and oriented along the Z-axis. I did a Far Field Request such that theta varies from -90 deg to +90 deg and phi=0 deg. In POSTFEKO I can see that the directivity vs. theta plot is exactly same as the gain vs. theta plot. Why is this so?
  10. Hello, I have modeled a linear array of dipoles along the X-axis (all dipoles being oriented along the Z-axis). All dipoles have been excited uniformly using voltage sources. According to the theory, the main beam can be steered if a progressive phase shift could be applied to the input. So, to achieve a 30 degree beam scan, I have assigned the phase (in the phase column of the voltage source dialogue box) to be 0, 30, 60, 90, ..., 720 starting from the first to the 25th dipole element. For this configuration it is expected to get the main beam at 120 deg, but I could get the main beam at 99.5 deg (I have attached the FEKO file here). What am I doing wrong? How can I get the desired scanning? Please suggest. Thank you in advance. uniform25.cfx
  11. Hi, I am trying to reproduce the results from the paper "The Active Element Pattern", by D. M. Pozar (attached below). In the paper, the author has considered an infinite array of planar dipole antennas and have obtained the active element pattern of a particular element. The active element gain pattern of the m-th element of the array is obtained by exciting only the m-th element and terminating all other elements in matched loads. According to the paper, if the element is excited with a voltage Vn=Voexp(-j k n a sin (theta)), where theta is the scanning angle, then there should be some dip or null observed in the active element gain pattern (at a certain scanning angle). I have simulated an array of 25 simple dipoles in FEKO where the dipoles are placed along the X-axis on the X-Y plane with each dipole oriented along the Z-axis. I have excited only the 5th element with a voltage source (Magnitude (V) = 1 and Phase (degree) = 30) and have added loads (of 50 ohm) to the other elements. When I am observing the gain pattern in POSTFEKO it is not showing any dip or null. Why is it so? How can I get the results shown in the paper? Please suggest. 00310010.pdf
  12. Thank you Torben. It is working.
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