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EMC Analysis

EMC Analysis
TEM cell analysis with aircraft

Modelling a TEM cell measurement chamber
with an aircraft inside.

Radiation Patterns and Antenna Factors

The FEKO solution engine employs the Method of Moments (MoM) which makes FEKO ideally suited to the analysis of typical EMC antennas. The power of the MoM approach lies in the fact that only problem elements where currents flow are discretised (e.g. wires, metallic surfaces, dielectric body surfaces). Free-space regions are not discretised and no absorbing boundary conditions (ABCs) have to be set in the simulation. Array patterns or specified near-field values are directly computed from the resulting MoM currents, resulting in a highly efficient computational process.

 

Near-fields for Radiation Hazard Analysis

Radiation hazard analysis is customisable to suit the user's requirements. Near-fields can be specified on Cartesian, cylindrical or spherical coordinate systems to enable easy visualisation of the near-fields around any particular structure of interest. Isosurfaces can be drawn from computed near-field blocks to visualise the shape of a hazardous radiation boundary around an antenna.

 

Electrically Large Problems

Computational resource requirements scale rapidly as the electrical size of a geometry increases and requirements can easily outstrip available resources for electrically large problems. FEKO provides the following solution features for such problems:

  • An efficient out-of-core solver that swops matrix blocks to hard disk during processing, allowing the solution of large problems on computers with less main memory than the problem normally requires.
  • A highly efficient parallel processing implementation for multiprocessor computers.
  • The Multilevel Fast Multipole Method (MLFMM) which greatly reduces computational resource requirements over the conventional MoM.
  • Approximation techniques hybridised with the MoM, e.g. Physical Optics (PO).

 

Automotive EMC measurement with log periodic antenna and near field

Automotive EMC measurement installation
with log periodic source.

Shielding

FEKO can compute electric and magnetic shielding factors for metallic or dielectric enclosures of arbitrary shape with arbitrary openings cut into them. Shielding effectiveness is typically tested for two scenarios:

  • The enclosure shields internal cables or components from outside radiation. In this case a plane wave may be directed at the enclosure and field values computed inside the enclosure to test its effectiveness.
  • The enclosure shields the external environment from internally generated radiation. In this case the internal radiating components are modelled to acceptable levels of detail (e.g. simple dipoles, patch antennas) and the near- or far-field levels outside the box are computed.
  • Imperfections in screening material, e.g. skin effects or radiation penetration through walls of finite conductivity, may be taken into account.

Cable Harness Analysis (Radiation and Irradiation)

Cable_types_CADFEKO_new.png

Cable Types available.

Several methods can be used to solve shielded and complex cable bundles within their operating environment. The combined Method of Moments and Multi-Conductor Transmission Line Theory method (MoM/MTL) has been developed for cables with arbitrary current return paths. This technique can handle gaps in conducting surfaces, but requires cables to be shielded for weak coupling to external fields.  A 2D static FEM solver to Laplace's equation that calculates cable parameters allows for the inclusion of arbitrary cable bundles.

Broad-Band Applications

EMC analysis (e.g. computing the shielding factor of an enclosure) typically has to be done over a wide frequency band. Frequency domain solvers (such as FEKO) that employ standard linear or logarithmic frequency stepping take prohibitively long to execute for such problems. FEKO features Adaptive Frequency Sampling (AFS) to adaptively scan the frequency band of interest in fewer frequency points, while still resolving all resonances and other characteristics of the problem.

Other Applications

FEKO has many features that make it attractive for a variety of EMC simulations in addition to the examples listed here. Examples of these features and solution abilities include:

  • Real ground (earth) can be modelled with a reflection coefficient approximation or a rigorous Sommerfeld formulation.
  • PCB whether simple or multilayered, with or without ground planes can be modelled with special stratified media Green's function formulations.
  • Dielectric or magnetic bodies of arbitrary shape can be modelled with an equivalent surface discretisation (e.g. multiple homogenous bodies) or a volumetric mesh (e.g. highly inhomogeneous bodies).
  • Several hybrid extensions for higher frequency ranges allow simulations where the traditional MoM fails due to excessive computational resource requirements.

 

RADHAZ surface at discone on naval mast car_with_cables.png Cylindrical coaxial cavity near field

Radiation hazard zones around
naval mast with mounted
antenna.

Defining a cable path for cable coupling analysis.

Analysis of shielding due to a cylindrical, coaxial cavity.

Additional Information

Additional Information