Modeling Approach for Electromagnetic Simulation of Anechoic Chambers

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1 Bitte decken Sie die schraffierte Fläche mit einem Bild ab. Please cover the shaded area with a picture. (24,4 x 11,0 cm) Modeling Approach for Electromagnetic Simulation of Anechoic Chambers Ralf Kakerow, Raimund Baakes Continental Wetzlar, Germany Irina Munteanu CST AG Darmstadt, Germany Interior

Content EMC laboratory Anechoic Chamber modeling Hybrid absorbers New modeling approach The presented results have been obtained in close cooperation

2 Content EMC laboratory Anechoic Chamber modeling Hybrid absorbers New modeling approach The presented results have been obtained in close cooperation between CST and Continental Parametrizable chamber model Examples Field uniformity Radiated emission Conclusion R. Kakerow, R. Baakes, I. Munteanu, Continental AG 2

3 Continental Corporation Five Strong Divisions Chassis & Safety Powertrain Interior Tires ContiTech Vehicle Dynamics Engine Systems Instrumentation & Driver HMI PLT, Original Equipment Air Spring Systems Hydraulic Brake Systems Transmission Infotainment & Connectivity PLT, Repl. Business, EMEA Benecke-Kaliko Group Passive Safety & Sensorics Hybrid Electric Vehicle Body & Security PLT, Repl. Business, The Americas Compounding Technology Advanced Driver Assistance Systems (ADAS) Sensors & Actuators Fuel Supply Commercial Vehicles & Aftermarket PLT, Repl. Business, Asia Pacific Commercial Vehicle Tires Conveyor Belt Group Elastomer Coatings Two Wheel Tires Fluid Technology Power Transmission Group PLT Passenger and Light Truck Tires Vibration Control 3 R. Kakerow, R. Baakes, I. Munteanu, Continental AG

4 Contental Corporation Interior Division Interior Division Business Units Instrumentation & Driver HMI Infotainment & Connectivity Body & Security Commercial Vehicles & Aftermarket Instrument clusters Secondary displays Head-up displays Climate controls Haptic controls Faceplates Central input devices Roof controls Integrated centerstacks Cockpit modules Radios Connectivity &Telematics Multimedia Software and Solutions Body control units Exterior light control units Power closures Seat comfort systems Battery & energy management Access control systems Tire information systems Intelligent antenna modules Tachographs & services Vehicle control units for drive & onboard electronics Instrumentation & HMI Onboard toll units & telematics Wear parts, spare parts & services for the independent aftermarket Original equipment services R. Kakerow, R. Baakes, I. Munteanu, Continental AG 4

5 EMC Laboratory Anechoic Chamber Modeling R. Kakerow, R. Baakes, I. Munteanu, Continental AG 5

6 EMC laboratory Automotive electronic devices need to pass various validation tests before entering the final application Performance (functionality against specification) Environment (thermal, vibration, dust, moisture, aging, ) Electromagnetic Compatibility (radiated and conducted RF, transients, ESD) Validation tests are expensive Equipment cost Test setup development EMC Tests are usually well specified, but the compatibility of test setups is limited Cables, connectors, etc. are usually different s-parameters Anechoic Chambers are not really identical anechoic chamber model R. Kakerow, R. Baakes, I. Munteanu, Continental AG 6

7 Motivation Regulations for EMC test have changed over the years CISPR-25 standard has been known as industrial quasi-standard for automotive The European Norm for E-Marking (RL72/245/EWG) has legislative character for EMC tests of automotive electronic devices Contains definition of DUT and antenna positions, table height, and distances to chamber wall Most significant change during the last years was the reference to CISPR-25 standard Many old anechoic chambers that not fully comply to CISPR-25 standard still exist Their compatiblility with the current standards needs to be discussed Understanding the field effects during EMC test ( chamber planning, test setup, ) R. Kakerow, R. Baakes, I. Munteanu, Continental AG 7

8 Anechoic chamber modeling Chamber size: 5.16m x 4.36m x 2.88m 21,200 pyramid absorbers on a hybrid absorber structure results in 134,624,388 meshcells Material properties are unknown R. Kakerow, R. Baakes, I. Munteanu, Continental AG 8

9 Hybrid absorber reflectivity Absorbers are composed as hybrid structure Ferrite tiles Foam absorbers Mounting layers, shielding foil, Reflectivity in db (magnitude) 0,00 4,74-10,00 241,65 478,55 715,46 952,37-20,00-30,00-40,00 180,00 135,00 90,00 45,00 0,00-45,00-90,00-135,00-180,00 Reflectivity in db (phase) Drawings and measurement data with courtesy of Frankonia EMC Test-Systems GmbH, Forchheim, Germany R. Kakerow, R. Baakes, I. Munteanu, Continental AG 9

10 Hybrid absorber modeling approach Existing approaches Full pyramids Finite-thickness layers Thin layers only with Ray Tracing Modeling based on measurements: Nontrivial task Often measurements provide only the magnitude Measurements are typically performed with normal incidence anisotropy cannot be taken into account Fitting of frequency data by low order rational functions is difficult, especially if the input data are affected by errors. Nevertheless, depending on the required accuracy, reasonably good models are possible Field uniformity standards: field values 75% of the measured points must differ by no more than 6 db R. Kakerow, R. Baakes, I. Munteanu, Continental AG 10

Surface impedance model based on reflectivity measurement Use infinitely thin surface impedance type equivalent material Fitting procedure of the material model parameters directly from the

11 Surface impedance model based on reflectivity measurement Use infinitely thin surface impedance type equivalent material Fitting procedure of the material model parameters directly from the measurements Transmission line model e, m, T matrix for layer of thickness h : A B cos( kh) j sin( kh) T C D j sin( kh) / cos( kh) Measured: reflectivity (S11) S 11 0 A B 0 0 C D A B C D f S S ( ) 11 11target Nonlinear function needs to be solved =0 Z s V 1 AZ L B I CZ D 1 L R. Kakerow, R. Baakes, I. Munteanu, Continental AG 11

12 Surface impedance model based on reflectivity measurement II Algorithm Input data: layer thickness h, assumed permittivity e and permeability m 1) Smoothen/downsample the measured data. 2) For each frequency, solve nonlinear eq. such that to determine parameter matrix T f S S ( ) target 3) Determine the surface impedance Zs(f) at each frequency point f. These Zs values can be used directly in a frequency-domain simulation. 4) For a time-domain simulation, use a fitting procedure on the large number of Zs values calculated in 3) to generate an analytical material model of the type N M 0, n j n 1, n Z( ) Z j L 2 j j n 1 n n 1 0, n 1, n Automatic fitting from MWS is used to create the reduced order model R. Kakerow, R. Baakes, I. Munteanu, Continental AG 12

13 Verification of the material model TD & FD simulations in CST MWS Frequency-dependent surface impedance ( Tabulated Zs ) Model: Infinitely thin material object placed in a waveguide (thickness not meshed) T (fitted Zs) F-solver Measured R. Kakerow, R. Baakes, I. Munteanu, Continental AG 13

table geometries antenna position and properties probe locations Floor covered with ferrite or full/partial

14 Parametrizable anechoic chamber model Generic and paramerizable chamber model Quickly adaptable to typical geometries for component level test Parametrizable to adapt chamber size ground plane and straps measurement table geometries antenna position and properties probe locations Floor covered with ferrite or full/partial with ground plane Surface impedance model for walls and ceiling R. Kakerow, R. Baakes, I. Munteanu, Continental AG 14

15 Application: Field Uniformity R. Kakerow, R. Baakes, I. Munteanu, Continental AG 15

Field uniformity simulation IEC61000-4-3: 16 E-field probes at predefined locations Uniformity measurement needs to be performed with empty chamber Ground plane needs to be removed

16 Field uniformity simulation IEC : 16 E-field probes at predefined locations Uniformity measurement needs to be performed with empty chamber Ground plane needs to be removed Field values for 12 probes (75%) must be within 6dB field is considered uniform Simulation between 1 GHz and 2 GHz using horn antenna R. Kakerow, R. Baakes, I. Munteanu, Continental AG 16

17 Representative E-field probe Comparison of the new modeling approach with a 3D-model of the pyramidal absorbers R. Kakerow, R. Baakes, I. Munteanu, Continental AG 17

18 Representative E-field probe Comparison of the new modeling approach with a 3D-model of the pyramidal absorbers R. Kakerow, R. Baakes, I. Munteanu, Continental AG 18

19 Comparison of computing resources Number of DOFs Computing time / min Speedup factor Pyramidal absorbers 960 million Thin sheet model 283 million times faster computing time R. Kakerow, R. Baakes, I. Munteanu, Continental AG 20

Electric field strength Empty chamber Fully equipped chamber Vertical component of the electric field strength at 1 GHz, at the DUT location Blue color indicates the limit of the 0-6 db field

20 Electric field strength Empty chamber Fully equipped chamber Vertical component of the electric field strength at 1 GHz, at the DUT location Blue color indicates the limit of the 0-6 db field homogeneity area Effect of ground plane, equipment etc. can be visualized Simulation shows field distribution in the entire chamber (while the test according standard just considers 16 probe locations) R. Kakerow, R. Baakes, I. Munteanu, Continental AG 21

21 Application: Radiated Emission R. Kakerow, R. Baakes, I. Munteanu, Continental AG 22

22 chamber height Setup for radiated emission antenna distance to ceiling dipole radiator T F C B R. Kakerow, R. Baakes, I. Munteanu, Continental AG 23

23 E-field at antenna center C R. Kakerow, R. Baakes, I. Munteanu, Continental AG 24

24 E-field at antenna top T R. Kakerow, R. Baakes, I. Munteanu, Continental AG 25

25 100 MHz Wetzlar chamber R. Kakerow, R. Baakes, I. Munteanu, Continental AG 26

26 100 MHz CISPR25 compatible chamber R. Kakerow, R. Baakes, I. Munteanu, Continental AG 27

27 30 MHz R. Kakerow, R. Baakes, I. Munteanu, Continental AG 28

28 618 MHz Wetzlar Chamber R. Kakerow, R. Baakes, I. Munteanu, Continental AG 29

29 Conclusion EMC test according to given standards is well established Optimization of test setups or contribution to standardization is still based on decades of experience Anechoic chamber modeling helps to understand many effects A new modeling approach for anechoic chamber absorbing walls has been presented Equivalent surface impedance model instead of detailed absorber geometries Simulation run-time and hardware requirements are reduced The approach has been applied to field uniformity and radiated emission examples Research on this topic is still ongoing Many thanks to Peter Weidner, Frankonia EMC Test-Systems GmbH, for the fruitful discussions and his valuable support R. Kakerow, R. Baakes, I. Munteanu, Continental AG 30

30 Thank you for your attention! R. Kakerow, R. Baakes, I. Munteanu, Continental AG 31

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