General Applicability of the Technique

Accurate MoM applied to source and triangular based PO applied to scattering region.

PO is formulated for use in instances where electrically very large metallic or dielectric structures are modelled. PO is an asymptotic high frequency numerical method of the same nature as the UTD, but is based on currents and not rays. Users will typically attempt a solution with the MoM at first and when they realise that the structure is electrically too large to solve with their available resources (platform memory, time) they will turn to the MLFMM and if they still can not solve the problem in the available resources, then PO.

Technical Foundation (Hybrid MoM/PO)

FEKO hybridises the current based accurate MoM with PO in the truest sense of the word with the bidirectional coupling between the MoM and PO being maintained in the solution, i.e. modification of the interaction matrix, ensuring accuracy. A practical example would be the calculate the effect on the input impedance of a horn antenna, treated with the MoM, when in close proximity to a large structure treated with the PO.

FEKO implements two special extensions to the PO:

• Fock currents to account for the effect of creeping waves over the shadow boundary region into "unlit" areas.

• Correction terms to achieve more accurate current representation close to edges and wedges.

Properties of the hybridization:

• FEKO triangulates a PO region, exactly the same as it would for a MoM solution, making it a simple task to switch between solution options.
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Typical Application of the PO

A typical example of how the MoM/PO hybridisation can be employed with good effect is in the analysis of reflector antennas. A large reflector antenna may be too large to analyse with the MLFMM, in which case a combination of MoM and PO is the ideal solution. The feed structure will typically be modelled with the MoM to achieve high accuracy in the currents on this part of the structure, with the reflector itself being modelled with the PO. Note that modal waveguide ports may be used in the MoM region of a hybrid MoM/PO analysis, enabling FEKO to deal very efficiently with horn feeds.

PO modelling of a reflector antenna with MoM modelling of the feed.