What are the main attributes of the asymptotic techniques?

Altair Forum User

What are the main attributes to take into consideration when selecting an asymptotic solution method in FEKO?

JIF

Attributes of the asymptotic techniques

The main attributes (both positive and negative) are listed below for each technique.

 

MoM/PO

• RWG basis functions, mesh size lam/10
• Back coupling from PO to MoM supported
• Multiple reflections computationally expensive
• Default #reflections =1
• Does not support diffraction around to the back of geometry

 

MoM/LE-PO

• Enlarged RWG, mesh size up to 2*lam
• Multiple reflections not supported
• Does not support diffraction around to the back of geometry

 

MoM/MoM-RL-GO

• Mesh must only resolve reflection angle off surface
• Back coupling from GO to MoM supported
• Multiple reflections less computationally expensive compared to PO
• Does not support diffraction around to the back of geometry

 

MoM/UTD

• No triangular mesh elements –  thus no restriction on frequency
• Back coupling from UTD to MoM supported
• Multiple reflections supported through “number of ray interactions”
• Supports diffraction around to the back of geometry (corner, edge, wedge diffraction)

 

What are these techniques good for and not so good for?

Suggestions on the applicability are listed below for each technique.

 

MoM/PO

• Mainly for metallic only problems, dielectrics can be included by modelling with a coating
• Where main field contribution are reflections that are (around) normal to surfaces
• Antenna placement and RCS
• Not good for antenna coupling if antennas are obscured from each other

 

MoM/LE-PO

• Same as PO but,
• When default PO mesh requires too many triangles
• No surface current can be displayed
• Nearfield requests too close to the surface (warning given in FEKO) will be ignored.

 

MoM/MoM-RL-GO

• When PO/LE-PO meshes require too many triangles
• When a dielectric is modelled 
• Antenna placement and RCS - required ray-launching angle could become quite small increasing resources

 

MoM/UTD

• When diffraction is important (no diffraction with PO and RL-GO)
• When PO meshes require too many elements
• Metallic only problems
• Antenna placement, antenna coupling – recommended to use point sources
• RCS is a problem due to caustics in the UTD