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Introduction to the FEKO Suite FEKO is a suite of tools that is used for electromagnetic field analysis of 3D structures. It offers several state-of-the-art
numerical methods for the solution of Maxwell’s equations, enabling its users to solve a wide range of electromagnetic
problems encountered in various industries.
Applications
Antenna Analysis
FEKO is well-suited to the analysis of wire antennas, horn and aperture antennas,
reflector antennas, microstrip antennas, phased array antennas, conformal
antennas, broadband antennas and more. Many special formulations enable the
analysis of practical antenna problems.
One example is a MoM-based solution
method that was designed specifically for the analysis of windscreen
antennas. Multiple layers of windscreen glass can be taken into account,
without meshing the glass. Antenna elements may consist of either wire
or metallic elements which are located inside a layer or on the boundary
between adjacent layers. Multiple windscreens may be included and
coupling with external geometry, e.g. a car body, is accurately modelled.
A full 3D MoM formulation is available for the analysis of microstrip
antennas with arbitrarily oriented metallic wires and surfaces in multi-
layered dielectric media. Interpolation tables are used for faster
simulation times.
FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd www.feko.info
Solution Methods Applications Special Features
Method of Moments (MoM), extended to
a wide range of applications e.g. dielectric
volumes, planar multi-layered structures,
dielectric and magnetic coatings, thin
dielectric sheets, ground plane reflections,
periodic boundary conditions
Multilevel Fast Multipole Method
(MLFMM)
Finite Element Method (FEM)
Physical Optics (PO)
Ray-launching Geometrical Optics (RL-GO)
Uniform Theory of Diffraction (UTD)
Multi-Conductor Transmission Line (MTL)
Theory
3D antenna design
Antenna placement
Microstrip antennas (planar
and conformal)
Microstrip circuits
3D RF components (waveguide)
EMC analysis (including
complex cable harnesses)
Bio-electromagnetics
Scattering analysis (RCS)
True hybridisation (MoM with FEM,
PO, RL-GO, UTD and MTL)
Adaptive Cross-Approximation (ACA)
Parallel processing
Optimisation
Adaptive frequency sampling
Circuit co-simulation
Domain decomposition
Time domain analysis
Low frequency analysis
GPU acceleration
Out-of-core solution
Wide range of hardware supported
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FEKO also offers solutions for mobile and wireless antennas. Inherent
parametric modelling and fast and accurate solvers provide quick insight into the
initial design performance. CAD import filters can be used to add mechanical
data, e.g. device housing and components, to the model. The optimisation
platform is ideal for automated modification of the geometry to meet user
specified goals.
Antenna Placement
Measurements of the radiation characteristics of antennas mounted on large
platforms are difficult or even impossible to perform, necessitating accurate
simulation. The MoM/FEM, MoM/PO,
MoM/RL-GO, MoM/UTD hybridisations and the MLFMM enable the analysis of
antennas in electrically large environments where the interaction with the nearby
structures influences the antenna characteristics, e.g. UHF antennas on aircraft or
ships or GSM antennas on motor vehicles. The visualisation of UTD rays can be
very informative in identifying high frequency scattering and reflection points.
EMC Analysis
FEKO is used extensively for EMC analysis, especially in the automotive industry. It
has also been used in various lightning protection and RFI mitigation studies. FEKO
can efficiently calculate the radiation patterns and antenna factors of EMC antennas. Another application is the
investigation of the shielding effectiveness of enclosures, whether metallic or made of non-perfect screening materials.
A special technique for metallic enclosures allows for shielding
factors of 200 dB or more to be computed. It is also a powerful
tool for the calculation and visualisation of surface currents and
near-fields, and is relied on by engineers to guide them in
electromagnetic interference (EMI) characterisation.
Cable Coupling Analysis
Many problems of electromagnetic compatibility and interference
involve cables, which either radiate through imperfect shields and
cause coupling into other cables, devices or antennas, or which receive external electromagnetic fields and then cause
disturbance voltages and currents which could potentially result in a malfunctioning of the system. FEKO is useful for
computing cable-to-cable and cable-to-device coupling and for the investigation of cable radiation effects. It can solve
both radiation and irradiation problems, through standard multi-
conductor transmission line (MTL) theory or its unique combined MoM/
MTL solution method.
Supported cable types include single conductor, ribbon, twisted pair,
predefined or specified coaxial cable, non-conducting elements and user-
defined cable bundles. If shielded, cables can be defined to have solid or
braided shields. FEKO provides an internal database listing the transfer
impedances for more than 20 popular cable types and additionally allows
users to specify their own cable transfer impedance and admittance
properties.
FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd www.feko.info Copyright 2013
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Bio-Electromagnetics and Biomedical Applications
While MoM offers efficient and accurate solutions for metallic structures,
FEM excels at simulation of inhomogeneous dielectric geometries, such as
human bodies. Therefore the hybridisation of these two methods is a natural
choice for the biomedical industry.
MoM can be employed to design or analyse the performance of the radiating
structure. Dielectric sheets or coatings can also be analysed efficiently, and a
dielectric half space can be used to mimic an anatomical load as an intermediate
simulation step. The final simulation of the radiator and detailed anatomical
phantom can be analysed with hybridised MoM/FEM, enabling accurate field
calculations inside the body for field propagation, dosimetry, SAR and safety
analysis. Typical applications include active and passive implants, hearing aids and
other body worn antennas, hyperthermia and RF tissue ablation, MRI and other
MW imaging technologies.
Radiation Exposure Safety Studies
The MoM or MLFMM may be used to compute near-field values around complex
building and antenna structures where people work. Isosurface plots are then
instrumental in determining where the safety boundaries conforming to
international radiation safety guidelines are located. Such information is typically
used to place signage and barriers at the site, ensuring safety of the public and
personnel in proximity to the transmitters.
The fields inside lossy dielectric regions may be used for computation of the Specific
Absorption Rate (SAR). FEKO reliably calculates the volume averaged SAR in 1g or 10g tissue cubes or as a whole body
average. It has been applied extensively in studies regarding the compliance of mobile phone antennas and cellular
base stations to international radiation exposure guidelines.
Microwave and RF Components and Circuits
Components such as filters, circulators, couplers, power dividers, mixers, isolators and
others can be simulated in FEKO. Multi-layer planar dielectric MoM for the analysis of
substrates can be used for the simulation of microstrip circuits. The FEM is available as
an efficient method for solving closed waveguide structures. Circuit co-simulation is
often used for feeding and matching networks. Circuit schematics can be created with
lumped elements, SPICE network models, S-, Z-
and Y-parameter blocks and networks specified by data from Touchstone files.
Time Domain Analysis
FEKO is based on a frequency domain formulation, but time domain information
can be obtained by applying Fourier Transforms on broadband frequency-
domain data. An interface is provided in POSTFEKO which facilitates users in the
specification of time domain pulse shapes. Time domain analysis has
successfully been applied to perform lightning strike analysis and to evaluate
time domain characteristics of ultra-wideband antennas, such as fidelity.
www.feko.info Copyright 2013 FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd
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The FEKO Suite
FEKO offers a graphical user interface (GUI) with easy workflow, running on Windows or Linux. The GUI can be used
every step of the way, from model creation in CADFEKO through to visualisation of results in POSTFEKO. Advanced
users can resort to EDITFEKO, a scripting interface to the FEKO solver, to obtain full control over functionality. The
scripting editor in POSTFEKO may be used for advanced post-processing of results.
The GUI provides 3D mouse support, which may be used as input device in addition to a keyboard and standard
mouse for convenient manipulation of 3D objects.
Modelling in CADFEKO
Functionality:
Interactive geometry specification.
Excitation and port definition.
Output requirement specification.
Optimisation setup.
Automated or custom meshing.
Solution control.
Features:
Create parametric models with variables and
mathematical expressions which may be modified
to change the geometry, meshing and/or material parameters (e.g. dielectric constant, coating, conductivity).
Create canonical structures (cylinders, polygons, spheres, cones, etc.) with the click of a button.
Perform boolean operations on geometry objects (e.g. split, union, intersect and subtract).
Define various types of curves and surfaces, including analytical curves, splines and NURBS surfaces.
Create geometry by spinning, sweeping and lofting lines and curves.
Translate, rotate, scale, mirror and align objects.
Project points, curves and surfaces onto surfaces or solids.
Add cables with user specifiable paths, shields and cross sections.
Create surface meshes (triangles) or volume meshes (tetrahedra) with specifiable mesh density for any specific
region of the geometry.
Import and export filters for complex geometry or mesh models in industry standard CAD formats.
Request multiple solution configurations, and set the following globally or per configuration:
Solution parameters (e.g. frequency, loads).
Excitations (e.g. voltage source, waveguide excitation).
Calculation parameters (e.g. far-fields, near-fields, S-parameters, SAR analysis).
View and add components to network and cable schematics.
FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd www.feko.info Copyright 2013
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FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd www.feko.info Copyright 2013
Choice of Solver and Resource Scaling
Full-wave techniques (MoM, FEM etc.) generally
suffer from poor scalability. This limits the
electrical size of the problems that can be solved
on typical computers. When using field based
solution techniques (FEM, FDTD), the
discretisation of the field introduces a very small error as a wave propagates through the mesh. For very large
meshes, these errors could add up, resulting in reduced accuracy in results. The error can be reduced by using a finer
discretisation, but this increases the resource requirements.
The MoM does not require field discretisation, which means that the propagation distance does not degrade the
accuracy of the results. With the MoM the memory required relates to the number of basis functions squared (N2).
For general structures, a basis function density of about 100 basis functions per λ2 is recommended. For 1 GByte
RAM, and using no symmetry, this translates to a surface area of approximately 82λ2 that can be solved in-core.
Larger problems can be solved using an efficient out-of-core solver in FEKO, but this solution is slower than an in-core
solution.
The memory requirements for MoM is proportional to N2, whereas that of the MLFMM is N*log(N) (for metallic
surfaces N ≈ 100*(A/λ2) with A the surface area). For large N this is a huge difference!
Although FEKO offers the MLFMM which enables the analysis of electrically large problems, this accurate full-wave
method is not sufficient for the solution of electrically huge structures (e.g. aircraft or ship at 10 GHz and above).
FEKO offers asymptotic high frequency techniques (PO, RL-GO and the UTD) as solution to the scalability hurdles in
such problems. In the PO formulation the currents on the metallic surfaces are simply calculated from the incident
field. Large element PO (LE-PO) allows mesh sizes of multiple wavelengths and although it does not support multiple
reflections, it can lead to dramatic computational cost savings in cases where it is applicable. The RL-GO works by
launching rays from each MoM element and placing Huygens sources on surfaces, while with the UTD only the closed
form reflection and diffraction (edge and corner) coefficients are used in the solution. The size of the object,
therefore, does not influence the memory requirement. The coefficients (terms) and the number of interactions do
however influence the run-time. The UTD formulation requires that the smallest dimension of the UTD objects be at
least in the order of a wavelength.
Asymptotic predictions of memory usage for the MoM with and without MLFMM
N MoM MLFMM Application
100,000 150 GByte 1 GByte Military aircraft at 690 MHz Reflector antenna with aperture size 19λ.
200,000 600 GByte 2 GByte Military aircraft at 960 MHz Reflector antenna with aperture size 27λ.
400,000 2.4 TByte 4.5 GByte Military aircraft at 1.37 GHz. Reflector antenna with aperture size 38λ.
1 000,000 15 TByte 12 GByte Military aircraft at 2.2 GHz Reflector antenna with aperture size 60λ.
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Whereas the triangles (for PO and RL-GO) are well suited to represent complex geometry, the use of flat polygonal
plates restrict the application of the UTD to geometries which can be modelled sufficiently with such plates (e.g. a
ship).
In FEKO, the generally applicable MoM has been hybridised with the Physical Optics (PO), ray-launching Geometrical
Optics (RL-GO) and the Uniform Theory of Diffraction (UTD). This hybridisation enables the solution of large problems
on small computers. The hybridisation allows for full wave analysis where required, and approximations to be used
when applicable.
Post-processing with POSTFEKO
Functionality:
Model validation.
Post-processing and visualisation of results.
Features:
Support for multiple 2D and 3D views with
multiple geometry (*.fek) and result (*.bof) files in
a single session.
Support for multiple results of the same type, e.g.
displaying more than one near-field ortho-slice in
the same 3D view.
2D results can be displayed in various formats on Cartesian graphs, polar plots and Smith charts.
3D views can be set up to display geometry, meshes, currents, near-fields and/or far-fields.
2D graph measurements and annotations for values such as local and global maxima and minima, beamwidth,
bandwidth and side lobe levels.
Multiple and arbitrarily oriented cutplanes with selectable cut entities are supported for 3D views.
Graph and data import and export (e.g. import of measurements for comparison purposes).
Full multiport S-parameter extraction.
Advanced Specific Absorption Rate (SAR) display options (IEEE standard compliant whole body average, 10g
cube localised, 1g cube localised).
UTD ray colours indicate their relative amplitudes.
Electrical surface currents and electrical charge density display options.
Characteristic mode currents, fields, eigenvalues, modal significance and characteristic angle display options.
Scripting based advanced post-processing as well as automation with the Lua POSTFEKO API.
Export of images and animations to popular file formats.
Automatic report generation via simple or template based mechanisms to MS PowerPoint, MS Word or PDF file
formats.
Visualisation of optimisation results.
Support for time domain results processing.
FEKO is a product of EM Software & Systems – S.A. (Pty) Ltd www.feko.info Copyright 2013