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.

Shahed 136 3D 해석 서페이스.png

Shahed136_PO_3D_1_9GHz.cfx

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