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Marcus Chang

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About Marcus Chang

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    Taiwan
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  1. Hi @Torben Voigt, It works now, the received power for RX antenna in situation of corner reflector is also 10 times larger than metallic sphere. Thanks for your suggestion! BR/Marcus
  2. Dear @Torben Voigt @mel @JIF, Recently, I try to run some simulations for metallic sphere and corner reflector respectively, the results for these simulation is weird, the received power bounced by metallic sphere is larger than corner reflector. But actually, the RCS for metallic sphere should almost 10 times smaller than corner reflector, no matter it's calculated by formula or simulated in FEKO (I also upload these simulations as attached, please check) So I would like to check with you again, to see what's happened to the setting in FEKO. BR/Marcus 190406.7z
  3. Dear @Torben Voigt, For the suggestion of the contribution of the surface currents of the sphere you provided, it seemed not work as below, there is no differences when I use it, please check: BR/Marcus 02_FF source_PEC sphere_sphere surface NF source_190325_sphere placed 72 lambda_alt.cfx
  4. Dear @Torben Voigt @mel @JIF MATLAB code is just a easy way to calculate it. But it is a simple and fundamental formula as below: while the RCS value I use is: here Gt=18.3=Gr, lambda=0.03(m), r=3*lambda, R=72*lambda (=2D^2/lambda, D=2*r) and Pt=1W (in Feko), then I can get the value of Pr is equal to 177nW, however, the results simulated in Feko is less than 100 nW. And thanks again for your suggestion of receiving far field pattern of reflected signal, I will try it and get back to you if there is any further questions. BR/Marcus
  5. Hi @Torben Voigt, Thanks for you support. About Mistake #2, the location of receiving antenna (RX) should be the same as transmitting antenna (TX). So I place the near field data at z=0 rather than z=0.2138m. (horn aperture is placed at z=0). Then I increase the distance between horn and metallic sphere to 72 times lengths of wavelength. (2*D^2/lambda=72 lambda) to satisfy far filed requirement, so that warning 39270 is not shown again. Finally I can get the results shown as below, please check: But... this results do not accord with the number calculated by MATLAB, the coding is shown as below, please check: f=10*10^9; c0=3*10^8; lambda=c0/f; %units: m lambda Pt=1; Gt=18.3; % simulated in FEKO Gr=18.3; % simulated in FEKO r=3*lambda %units: m, radius for metallic sphere RCS=pi*r^2 R=72*lambda %units: m, distance between sensor and object Pr=Pt*1*Gt*Gr*RCS*(lambda^2)/((4*pi*R^2)*(4*pi*R^2)*(4*pi)) so that I can get Pr=177.56e-09 (W), 177nW approximately, almost twice the power of the results (100nW) simulated in FEKO. Second question is, is it possible to get far field pattern of the reflected field of sphere? BR/Marcus onlyonechancy@gmail.com 190326.zip
  6. Hi @Torben Voigt, I already update attached file as below, please check it. BR/Marcus onlyonechancy@gmail.com NF for 10GHz horn.efe NF for 10GHz horn.hfe FF source_PEC sphere_sphere surface NF source_190312.cfs FF source_PEC sphere_sphere surface NF source_190312.cfx FF_for_10GHz_horn.ffe horn_X band_190309.cfs horn_X band_190309.cfx metallic_sphere_NF_for_10GHz_1.efe metallic_sphere_NF_for_10GHz_1.hfe temp_190313.cfx temp_190313.cfs
  7. Hi @Torben Voigt, Thanks for you immediately support, and it works now. Here is another question for another exercise, I would like to use a horn antenna to radiate on a metallic sphere, then try to use the same horn antenna to receive power reflected from the metallic sphere. First, I extract near field data from a horn antenna I just run (please check file named horn_X band_190309.cfs). Then in simulation 1 (please check file named FF source_PEC.......cfs), I use this near field source as TX and radiate to a metallic sphere, then I can get the results of the near field from a surface of sphere, and extract its as the near field source for simulation 2 (please check file named temp_190313.cfs) In simulation 2, I use the near field source from previous results (on surface of sphere) and radiate to a near field receiving antenna (the same horn antenna) and try to get the result that how much power it can receive. However, I get two different results from different method, one is using far field receiving antenna, another one is near field receiving antenna as below. And also, it is weird that the power is negative, could you please help us check again what's happening to this simulation? And the last question is, how could we get results of the far field pattern from receiving antenna, not just power calculation? BR/Marcus onlyonechancy@gmail.com temp_190313.cfs horn_X band_190309.cfs FF source_PEC sphere_sphere surface NF source_190312.cfs NF for 10GHz horn.efe NF for 10GHz horn.hfe metallic_sphere_NF_for_10GHz.efe metallic_sphere_NF_for_10GHz.hfe FF_for_10GHz_horn.ffe
  8. Dear all, I have an exercise which I would like to extract near field from a horn antenna and import to another simulation (all in FEKO platform), then there is a weird result shown in the video as below link I just uploaded: https://drive.google.com/file/d/1-NGAV75rxH2zKfahMF4qN6I2l8BpKN8c/view?usp=sharing You can see the far field pattern with near field source I imported is completely opposite to original one. I would appreciate if anyone can show me how to simulate correctly. BR/Marcus horn_X band_190309.cfs
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