CST EMC STUDIO®

Modelling of EMC emissions

All electronic devices must pass EMC emission standards tests. These standards are handled by the Federal Communications Commission (FCC) or the Comité International Special Pertubations Radioélectriques (CISPR). The military has its own – significantly more stringent – standards and guidelines that are specified in MIL-STD-461E or MIL-STD-464.

Electromagnetic simulation can help to ensure compliance already in the development stage. Correct EMC modeling must capture the important coupling mechanisms for conducted and radiated emissions. In many cases, a full 3D analysis is required in order to capture the stray fields coupling and the shielding effectiveness of enclosures.

A unique and indispensable technology for the analysis of electromagnetic emissions in the CST STUDIO SUITE® is definitely the coupling of 3D EM field simulation and SPICE equivalent network calculation. With the co-simulation capability, CST has set a new benchmark for accurate and efficient electromagnetic analyses. By means of this technique it is possible to investigate the interaction of 3D electromagnetic fields and complex cable harnesses without the need to subdivide the entire space into tiny mesh cells.

Furthermore, there is the possibility to split complex systems into smaller parts like Transmit PCB – Connector – Cable – Connector – Receive PCB, to calculate each part separately with specific solvers, and finally to cascade them in a network for a complete system analysis.

Susceptibility

Susceptibility, or immunity, is related to ensuring that the product will work in its intended environment without being disturbed.

There are many different electromagnetic phenomena which a product could be exposed to, these could be continuous phenomena such as transmissions from nearby antenna masts, or transitory phenomena such as the noise introduced onto the mains due to the switching of a device (eg fridge).

During testing, the performance of the product is monitored to determine if the disturbance causes a degradation in performance – depending on the test being carried out, and the type of product being tested, the level of allowable degradation varies. This ranges from no degradation at all through to user intervention being required to return the device to full functionality.

In terms of modelling, typically we would look at the level of signals coupled to cables or to connector pins, or received field strengths. The model can be subjected to both continuous and transitory disturbances. Through knowledge of the functionality and design of the product, the results can then be used to assess the likely impact on the performance. Different mitigation techniques, such as using transient suppressors or different shielding techniques, can also be assessed.

Electromagnetic Environmental Effects

Electronic systems may be susceptible to damaging Electromagnetic Environmental Effects (E3) that can arise from a variety of natural or man-made environmental sources.  These sources may include Electromagnetic Pulse (EMP), Radio Frequency Interference (RFI), High Intensity Radiated Fields (HIRF), Electromagnetic Interference (EMI), Electrostatic Discharge (ESD), Lightning Strikes and Precipitation Static (P-STATIC). Other concerns include the hazards of electromagnetic radiation to personnel, ordnance and volatile materials (RADHAZ). E3 applications often involve electrically large structures (aircraft, ships, land vehicles) containing critical detail (seams, cables). The EM sources can be frequency-domain based over a broad range, or transient waveforms. CST’s complete simulation technology is ideal for handling these multi-scale problems.
CST’s E3 applications include: full vehicle susceptibility analysis, enclosure shielding effectiveness calculation, test rig design/assessment and normalization to free space environments (e.g. lightning return conductor systems), cable design and shield transfer impedance extraction, prediction of induced currents/voltages in complex cable systems and performance of EMI filters, ferrites or non-linear transient protection circuits.

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CST EMC STUDIO®

The solvers included in CST EMC STUDIO have been selected to allow a wide range of EMC workflows to be carried out in a straight forward way.

  • The transmission line matrix (TLM) solveris time domain method which is especially well suited to EMC simulation. The TLM solver can use octree gridding to significantly reduce simulation time on extremely complex structures, and also supports analytic compact model representations of fine details.
  • The transient solver, based on the finite integration technique (FIT), is a general purpose time domain solver and is best suited to broadband simulations of radiated emissions and susceptibility.
  • The frequency domain solveris based on the finite element method (FEM), and is often used to simulate conducted emissions. The frequency domain solver includes a special meshing engine optimized for PCBs, which allows complex boards to be simulated faster than conventional methods.
  • The cable harness solver is a specialized solver for simulating cables in complex environments. There is a bidirectional coupling between the cable harness solver and the time domain solvers, allowing cable harnesses to be integrated into a 3D model and analyzed using bidirectional simulation.

CST DESIGN STUDIO supplements the 3D solvers with circuit simulation. Non-linear circuit elements can be included in a 3D simulation using true transient/circuit co-simulation. CST DESIGN STUDIO also allows models to be linked together through System Assembly and Modeling (SAM), making it possible to carry out hybrid simulations of systems built up of individual components.

In addition, CST EMC STUDIO also includes the EMC rule checker from CST BOARDCHECK. This can quickly analyze imported PCB layouts against a set of design rules, and highlight violations that may lead to EMC issues.

CST EMC STUDIO (CST EMCS) is a specialized software package for analyzing electromagnetic compatibility (EMC) and electromagnetic interference (EMI) using 3D electromagnetic field simulation. The solvers and tools in CST EMCS have been selected to be especially relevant to EMC engineers, and are drawn from the mature technology of CST STUDIO SUITE and CST BOARDCHECK.

The range of solvers allow emissions and susceptibility to be investigated across a range of different components. Alongside the general purpose time and frequency domain solvers, CST EMCS also includes cable harness solvers, EDA and CAD import tools, circuit simulation tools, PCB design rule checking and compact models for simulating vents and seams efficiently. With CST’s System Assembly and Modeling (SAM) framework, simulations of individual components can also be combined for a hybrid simulation. Through its dedicated EMC workflows, CST EMCS can be integrated into a wide range of product design processes.

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