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Mastertitelformat bearbeitenOutline

O What is openEMS?O Concept of circuit simulation based superpositionO TheoryO Simple example

O Show cases in openEMSO Conclusion

19.05.2016 / EDUHF-LAB MRI, Magdeburg Jan Taro Svejda 2

Mastertitelformat bearbeitenWhat is openEMS?

O openEMS is …O … a 3D electromagnetic field solverO … open-source (licensed under the GNU GPL)O … suitable for Linux, Windows

O Controlled byO Matlab™ (commercial) orO Octave (open-source)

O Postprocessing directly in Matlab/OctaveO Field plots with

O Paraview (open-source) orO Matlab/Octave


Mastertitelformat bearbeiten

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What is openEMS?

O Field calculations based onEC-FDTD1 schemeO Time domain method ! broadband solutionO Resources scale linearly with problem sizeO Simple integration of advanced dispersive

material modelsO Calculations in …

O … Cartesian coordinates andO … Cylindrical coordinates


1 equivalent circuit (EC) - finite-difference time-domain (FDTD)

Mastertitelformat bearbeitenCircuit simulation based superposition

O Purpose

1. Replace lumped components withlumped ports

2. Carry out full wave simulation for each port

3. Take S-parameters to circuit simulationand apply complex network

4. Use the resulting currents for complexweighted field superposition




[1] K. Karlsson, et.al., “Optimization of antenna diversity gain by combining full-wave and circuit simulations”, in Proc. Second European Conference in Antennas and Propagation EuCAP 2007, Nov. 2007




O AdvantageO Fast computation of fields when only

network (lumped elements) has changedO Simple and fast calculation of total fieldO Highly suitable for optimisation Problems

O DisadvantageO Full wave simulation for each port necessary

O Increase of simulation time …… but: due to terminations no resonant structure(quick single simulations)

O Structural change leads to complete new simulation (for each port)



O Easy implementation in openEMS

O With script in Matlab/OctaveO Small circuit simulation tool-box (CTB)

included in openEMSO Further computation in other

circuit simulation software:O Advanced Design System (ADS)™ (commercial) orO Qucs (open-source)

O All possible optimisation routinesare useable in Matlab/Octave Postprocessing


Mastertitelformat bearbeitenShow cases

O Single loop coilO Capacitors and Matching Network

O 6 channel array of loop coilO Cylindrical coordinatesO Worst case SAR -> Safety

O Non-circular shaped birdcageO Optimisation of capacitors

for high polarisation purity


Mastertitelformat bearbeitenShow case:Single loop coil for head

O Simulation setupO 3 capacitors (red) for tuningO Matching network at port 1 (blue)





O Optimized S-parameters (tuning/matching)O Tuning in MatlabO Matching with ADS





O Simulation setup:O Use of cylindrical coordinates






Mastertitelformat bearbeitenShow case:Non-circular shaped birdcage

O Simulation setup:O One half of birdcage flattenedO 16 rungs involved, each with one capacitor





O Optimized fieldsO Excitation with two ports

and quadrature phase difference


Mastertitelformat bearbeitenConclusion

O openEMSO Free and open-source EC-FDTD solverO Supports Cartesian and Cylindrical coordinatesO All (dis)advantages of FDTD schemeO Controlled by powerful Matlab/Octave interface

O Parameterized structureO Postprocessing directly in Matlab/OctaveO Arbitrary optimisations

O Circuit simulator feature includedO Circuit simulation based superposition

O Highly suitable for non structural optimisationsO Simulation for each port/lumped element

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BioEM-Workshop'16 JanTaroSvejda komp · O All (dis)advantages of FDTD scheme O Controlled by...

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