How to obtain 3 Dimensional RCS(and result vallidation)

Yun_20312

I'm currently using altair feko to get RCS of CAD model(model is from GrabCAD). 

for the RCS data, I wanted to get 3 dimensional RCS.

so I modified plane wave sources, start angle and end angle.

for elevation angle, it starts from 0 and increased up to End angle: 180 degree

and for azimuth angle, it starts from 0 and increased up to 360 degree.

you could check the setting in my cfx file.

finally I applied Physical Optics solver, and run feko.

here, my first question is: is it a vallid way to gain 3 dimensional RCS? 

second, in the Total RCS data I acquired, there are a lot of blue colored area which means 0 RCS. does it mean the way I did was wrong?

I attach cfx file and screen capture of resultant RCS.

Torben Voigt

Hi Yun,

PO (LE-PO in your case) is an asymptotic solver, which means that it is used when full wave solvers such as MoM or MLFMM are no longer efficient (too much memory, too long runtime). PO (LE-PO) naturally has limitations compared to full wave solvers that need to be considered. This is mainly the fact that no interactions between PO faces are calculated and that there are no diffraction effects. Where the plane wave does not reach (shadow region), the currents are correspondingly zero. Also keep in mind that the model contains some details that are not electrically large. Asymptotic solvers may not take these into account accurately.

I'm not saying that the results would be significantly different with full wave solver, but there is the possibility. Ideally, you should test this.

If you want exact results, you should try to calculate the model with MoM and CBFM (Characteristic Basis Functions Method). MLFMM is not recommended here due to the many plane waves, as each direction of incidence would mean a complete simulation. With MoM, the number of excitations would not be a problem.

MoM with CBFM is available in the current version Feko 2023. Your model apparently comes from a much older version (Feko 2021?).

Note: You can simplify your model by deleting redundant faces (e.g. PEC face between two PEC regions) with "Simplify".

Best regards,
Torben

Torben Voigt

You could also consider using only one half of the plane wave directions, as the model appears to be symmetrical.

Yun_20312

Torben Voigt_20420 said:

Hi Yun,

PO (LE-PO in your case) is an asymptotic solver, which means that it is used when full wave solvers such as MoM or MLFMM are no longer efficient (too much memory, too long runtime). PO (LE-PO) naturally has limitations compared to full wave solvers that need to be considered. This is mainly the fact that no interactions between PO faces are calculated and that there are no diffraction effects. Where the plane wave does not reach (shadow region), the currents are correspondingly zero. Also keep in mind that the model contains some details that are not electrically large. Asymptotic solvers may not take these into account accurately.

I'm not saying that the results would be significantly different with full wave solver, but there is the possibility. Ideally, you should test this.

If you want exact results, you should try to calculate the model with MoM and CBFM (Characteristic Basis Functions Method). MLFMM is not recommended here due to the many plane waves, as each direction of incidence would mean a complete simulation. With MoM, the number of excitations would not be a problem.

MoM with CBFM is available in the current version Feko 2023. Your model apparently comes from a much older version (Feko 2021?).

Note: You can simplify your model by deleting redundant faces (e.g. PEC face between two PEC regions) with "Simplify".

Best regards,
Torben

Thank you for answering my question sir, It was really helpful and now I figured out what I did wrong, I didn't even considered the 'shadow region' as you said. 

actually I ran RCS analysis with MoM with lower frequency, and I think I could get the result that has not many 0.0 RCS values.