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Hi,
I am trying to simulate the propagation of of EM waves through the ground as well as the reflection from the surface. The main problem with the cad software that I used (HFSS, CST, Semcad) is the PML boundary conditions ? They seem to work only for a single background material and not for...
Are you talking about MATLAB license issues (limit on maximum matrix size for some versions) ? You might want to use the 64bit version of MATLAB in this case your maximum matrix size is not limited to 2GB.
Another trick is to use single precision matrices (half the memory), you have to make...
Reciprocity theorem in antenna context are usually used to refer to identical radiation pattern for reception and transmission (as GKG said) or that swapping the receiving and transmitting antenna results in the same received signal.
Adel
I agree. I use HFSS and I am getting pretty good results compared to measurements for planar antennas.
I think CST/SEMCAD is better when your structure is electrically large since FDTD (CST,SEMCAD) does not require as much RAM as FEM (HFSS).
Adel
it really depend on your design. The bottom line is that the slot should be quarter wavelength if it is open from one end. If the slot is closed on both sides then it should be half wavelength. This has to do with the resonance modes of a slot line resonator.
Hello Azulykit,
The inclusion of the mismatch loss in the antenna gain is mainly dependent on the Friis transmission equation you are using. The most common one is:
Pr = Pt *Gt * Gr * (lmda/(4pi R))^2 * (1-|S11|^2) * (1-|S22|^2) * Polarization_loss_factor.
and as you see it separates the...
dipole close to the ground
Hi,
placing a dipole too close to a ground plane means that its matching will be severely affected (because of the cancellation between the direct field and the reflected field) as you said. But the gain will be higher. This is correct because the gain is calculated...
when solving for waveport, hfss solves the 2D eigen value problem to find the propagating modes in the waveguide, their characteristic impedance and their propagation constants. It does not actually solve the structure, so you won't be able to find S11 or the radiation pattern for example...
I don't think you can using the user interface in HFSS. The only way I remember was using a script that you get from Ansoft support, this is usually used for FSS simulations.
coax cable in CST
You can draw a coaxial cable by drawing a pec cylinder and inserting a dielectric cylinder in it with inner and outer radii corresponding to the radius of the inner conductor and the radius of the outer conductor.
The most commonly used dielectric in coaxial cable is Teflon...
Please comment on my NEGATIVE gain, need help.
Negative gain (I am assuming it is in dB ) means that your structure has too much losses and/or very badly matched. But if you mean a negative gain at certain direction, this is normal, you should get positive gain at some angles and a negative...
I understood that you are trying to solve an eigenvalue problem using MoM. But I do not understand what do you mean by zeros ? You mean zeros in the impedance matrix or zeros in the eigenvalues ?
Also, as I remember, for MoM, increasing the number of unknowns beyond a certain limit does not...
Yes, this problem is really annoying in many structures. But I think (I did not try it myself though) the new CST tetrahedral mesh should solve this problem but you will need to solve in the frequency domain rather than the time domain in this case.
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