Feko is a comprehensive electromagnetic solver with multiple solution methods that is used for electromagnetic field analyses
involving 3D objects of arbitrary shapes.

EDITFEKO is used to construct advanced models (both the geometry and solution requirements) using a high-level scripting language
which includes loops and conditional statements.

One of the key features in Feko is that it includes a broad set of unique and hybridised solution methods. Effective use of Feko features requires an understanding of the available methods.

Solver methods can be categorized as either source-based methods or field-based methods. Understanding the main differences
between these two categories helps to understand and choose an appropriate solution method for each application.

The Solver includes multiple frequency and time domain solution methods. True hybridisation of some of these methods enables efficient
analysis of a broad spectrum of electromagnetic problems. You can also use more than one solver method for cross-validation
purposes.

Full wave solutions rigorously solve Maxwell's equations without making any assumptions regarding the nature of the electromagnetic
problem. The solution can be either in the frequency or the time domain.

The testing of the integral equation applies the integral equation over each triangle edge to obtain N equations with N unknowns which can readily be solved on a computer.

Summing or integrating the vector currents is the last step in the MoM procedure. This step leads to specific output parameters such as far fields and impedance.

The usage of a dense matrix in the MoM implies a limit to the size of the problem that can be solved. The limit is determined by the available computational
resources.

The multilevel fast multipole method (MLFMM) is an alternative formulation of the technology behind the method of moments (MoM) and applies to much larger structures (in terms of the wavelength) than the MoM, making full-wave current-based solutions of electrically large structures a possibility.

The relevant integral equation method can be used to solve a model to either obtain faster iterative or higher numerical
accuracy when using the MoM or MLFMM.

The adaptive cross-approximation (ACA) is a fast method similar to the multilevel fast multipole method (MLFMM) but is also applicable to low-frequency problems or when using a special Green’s function.

The finite element method (FEM) is a solution method that employs tetrahedra to mesh arbitrarily shaped volumes accurately where the dielectric properties
may vary between neighbouring tetrahedra.

The finite difference time domain (FDTD) is a full wave time domain solution method, and Fourier transforms are applied to convert the native time domain results
to the frequency domain.

Asymptotic solution methods solve Maxwell's equations, but make certain assumptions regarding the nature of the problem.
Feko provides various high frequency asymptotic solution methods that assume the frequency of interest is high enough that
the structure is much larger than the wavelength.

The windscreen antenna solution method reduces the computational requirements by meshing only metallic elements while analysing
the behaviour of the integrated windscreen antennas within their operating environment. The analysis can take into account
the physical features of windscreen antennas and their surroundings.

Feko offers state-of-the-art optimisation engines based on generic algorithm (GA) and other methods, which can be used
to automatically optimise the design and determine the optimum solution.

Feko writes all the results to an ASCII output file .out as well as a binary output file .bof for usage by POSTFEKO. Use the .out file to obtain additional information about the solution.

CADFEKO and POSTFEKO have a powerful, fast, lightweight scripting language integrated into the application allowing you to create
models, get hold of simulation results and model configuration information as well as manipulation of data and automate
repetitive tasks.

One of the key features in Feko is that it includes a broad set of unique and hybridised solution methods. Effective use of Feko features requires an understanding of the available methods.

The Solver includes multiple frequency and time domain solution methods. True hybridisation of some of these methods enables efficient
analysis of a broad spectrum of electromagnetic problems. You can also use more than one solver method for cross-validation
purposes.

Full wave solutions rigorously solve Maxwell's equations without making any assumptions regarding the nature of the electromagnetic
problem. The solution can be either in the frequency or the time domain.

Summing or integrating the vector currents is the last step in the MoM procedure. This step leads to specific output parameters such as far fields and impedance.

Summing or integrating the vector currents is the last step in the MoM procedure. This step leads to specific output parameters such as
far fields and impedance.

The Free Space Green Function

The free space Green's function is essential to the MoM to
allow calculation of fields at arbitrary points in 3D space. Without going into the finer
technical details of the equation, it can be stated that the Green function is contained inside
the integral operator $\mathcal{L}$ operating on the surface currents,

Consider an infinitesimally small current element J in free
space at a point r' radiating an electric field E and a magnetic field
H.

The Green's function (Equation 2) gives the spatial response to a spatially impulsive current source. This means
that for the current element (source) located at the point r', the Green's function gives
the potential of this source at the point r, or any required point in 3D space.

the distance from the source to the field point. When there are
multiple of these sources distributed in space, such as over the arbitrary PEC body, the
response at the point r is given by summing all the sources (integration over all the
sources).^{1}

^{1} Computational Electromagnetics for RF and Microwave Engineering, Second Edition,
David B. Davidson, p.265