Calibration and Validation for Automotive EMC

Transcription

1 Calibration and Validation for Automotive EMC Wolfgang Müllner Patrick Preiner Alexander Kriz Seibersdorf Labor GmbH 2444 Seibersdorf, Austria

2 Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 2

3 ALSE Performance Validation Standard: CISPR 25 Frequency range: 150kHz 1GHz Two methods: reference measurement method modelled long wire method Wolfgang Müllner 3

4 900 mm 1000 mm 900 mm 250mm 750 mm ALSE Performance Validation Reference Measurement Method (RMM): 1000 mm 1000 mm P3 Reference test site for calibration of Setup: OATS Transmit antennas: small monopole and small biconical antenna Corresponding measurements in ALSE ALSE measurements must be within defined tolerances RX Monopole 100mm 1000 mm Monopole TX Monopole TX Monopole Test bench Monopole RX Ant. 100mm 1000 mm P2 TX Ant. P1 Test bench test bench test bench 100 mm 100 mm Wolfgang Müllner 4

5 LWA Antenna 900 mm 1000 mm LWA Antenna 900 mm ALSE Performance Validation Modelled Long Wire Method (LWM): 50cm long wire as TX antenna Measurements with the long wire in 100 mm test bench 100 mm test bench the ALSE Measurements are compared to the Monopole 50 Ohm termination 500 mm 50 Ohm termination 500 mm modelled (simulated) fields RF cable RF cable ALSE measurements must be within 1000 mm 1000 mm defined tolerances 1000 mm 1000 mm Monopole LWA Antenna (5cm above GP) test bench test bench 100 mm 100 mm (CISPR 25) Wolfgang Müllner 5

6 Delta [db] Delta [db] ALSE Performance Validation Purpose of this Validation: compare the radiation characteristic of the ALSE setup table with the reference data (calibration or simulation) Limit: ±6dB Criterion: 90%of measured points within limit RMM LWM points out of 481 exceed 6 db (= 15.59%) points out of 481 exceed 6 db (= 8.73%) Frequency [MHz] Frequency [MHz] Wolfgang Müllner 6

7 900 mm 1000 mm 900 mm 250mm Delta [db] 750 mm ALSE Performance Validation Results RMM: OUT OF SPEC!!! 20 RMM points out of 481 exceed 6 db (= 15.59%) RX Monopole 1000 mm TX Monopole TX Monopole RX Ant mm P3 P2 TX Ant. P mm Test bench 100mm Test bench mm 1000 mm Monopole Monopole test bench test bench Frequency [MHz] 100 mm 100 mm Wolfgang Müllner 7

8 ALSE Performance Validation Results RMM: OUT OF SPEC bonding is critical!!! Wolfgang Müllner 8

9 Delta [db] ALSE Performance Validation Results LWM: WITHIN SPEC!!! LWM points out of 481 exceed 6 db (= 8.73%) Frequency [MHz] Wolfgang Müllner 9

10 Regular ALSE Re-Calibration Regular Re-Calibration of ALSE ALSE is test equipment Needs regular calibration (ISO requirement) Certain time interval (1-5 years) Anytime a change in the ALSE is made: Setup Table Bonding Antennas Absorbers Wolfgang Müllner 10

11 Delta [db] Regular ALSE Re-Calibration LWM points out of 481 exceed 6 db (= 8.11%) 34 points out of 481 exceed 6 db (= 7.07%) Frequency [MHz] Wolfgang Müllner 11

12 Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 12

13 Antenna Calibration Standard: SAE ARP 958 Determining the Antenna Factor (AF) OATS (d=1m; h=3m) (SAE ARP 958) Wolfgang Müllner 13

14 Antenna Calibration (SAE ARP 958) Determining AF (d=1m; h=3m) E = AF + U (E [dbµv/m]; U [dbµv]; AF [db/m]) Using two identical antennas G = 4πr λ V R AF db = 20 log log (G) V T λ (SAE ARP 958) (SAE ARP 958) Wolfgang Müllner 14

15 Antenna Calibration (SAE ARP 958) Three antenna method: antennas can be different 3 measurements: A2-A1, A3-A1, A3-A2 AF 1 db = 10 log f M (E max D + A 1 + A 2 A 3 ) AF 2 db = 10 log f M (E max D + A 1 + A 3 A 2 ) AF 3 db = 10 log f M ( E max D + A 2 + A 3 A 1 ) Wolfgang Müllner 15

16 Antenna Factor [db/m] Antenna Factor [db/m] Antenna Factor [db/m] Antenna Calibration (SAE ARP 958) Frequency [MHz] Biconical antenna Frequency [MHz] Log. Per. antenna Frequency [GHz] Horn antenna Wolfgang Müllner 16

17 Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 17

18 LISN Calibration LISN Line Impedance Stabilization Network Used for Conducted Emission Measurement To supply the EUT with proper power To suppress the RF voltage of the mains To conduct the RF voltage to the EMI receiver To terminate the power cord with a defined impedance 18

19 LISN - Defined Impedance? Impedance between conductor and reference earth Device: mains plug Automotive components: cable shoe or plug 19

20 LISN - Calibration Jig 20

21 LISN - Calibration procedure Set vector network analyzer (VNA) to S11 Perform 1-Port Open-Short-Load calibration Connect LISN via calibration jig Calculate impedance using Z = 50 1+S 11 1 S 11 Z is impedance of LISN 21

22 LISN - Requirement of CISPR Tolerance Absolute ± 20 % Phase ± 11.5 Ref. [1] 22

23 Same Calibration Result if The calibration jig has no influence to the result Everybody uses the calibration jig delivered by the manufacturer of LISN Everybody builds the calibration jig according to the design given by the manufacturer in the manual of the LISN If the systematic error from the calibration jig is corrected 23

24 Impedance [ ] Different calibration jigs will lead to Jig A Jig B Limit Frequency [MHz] 24

25 Scientific approach to solve problem Definition of the measurand Calibration plane Development of a model for the calibration jig Equivalent circuit Characterization of equivalent circuit Calculation Measurement Correction of systematic error 25

26 Correction Circuit Formula Z VNA C L Z LISN 1 Z VNA = 1 jωc + jωl + Z LISN 26

27 Impedance [ ] Calibration plane: Cable shoe Calibration plane cable shoe Jig A Jig B Jig A corrected Jig B corrected Limit Frequency [MHz] 27

28 LISN - Conclusion Calibration jig has influence on impedance result Absolute value: small influence Phase: large influence Characterization and correction possible Simple C L Model Clear definition of the measurand required Impedance Calibration plane 28

29 Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 29

30 Field Probe Calibration Calibration factor versus frequency Calibration factor for different orientations Isotropy test (setup depends on use of probe) Frequency combinations (user defined) Linearity at a certain frequency (user defined) Wolfgang Müllner 30

31 Calibration Methods Calibration using calculated field strengths. The field sensor under test is placed in a calculated reference field based on the geometry of the field source and the field source s measured input parameters. Calibration using a primary standard (reference) sensor that contains no active or passive electronic devices and has its calibration traceable to a national standards laboratory based on international standards. Calibration using a transfer standard (a field sensor similar to the one being calibrated), that has traceability to a national standards laboratory. Wolfgang Müllner 31

32 Calibration Methods Calibration using calculated field strengths. TEM Cell Calibration using a primary standard (reference) sensor Precision Reference Dipole PRD sensor Calibration using a transfer standard Substition Method d d Wolfgang Müllner 32

33 Calibration Methods Methods deliver relatively low field strength Automotive Company standards require higher field strength: EMC-CS (Ford) STD (Volvo) GMW 3097 (GM) GS _07_2013 (BMW) Solution: Reverberation Chamber High field strength resulting from repeated reflections from the conducting surfaces is a superposition of plane waves Wolfgang Müllner 33

34 Reverberation Chamber (RC) SG Amp Power Meter Reverberation Chamber Read Out

35 Field Strength [V/m] Power [W] Reverberation Chamber (RC) Field Strength Field Strength Limit Power Achievable Field Strength: GHz: 1200 V/m GHz: 600 V/m GHz: 300 V/m Frequency [GHz]

36 Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 36

37 What is a System Check? A System Check is a quick and reliable method to increase the confidence in measurement results of the test engineer the test lab and the customer. It detects failures in the measurement system: receive antenna, pre-amplifier, cable, spectrum analyzer, measurement software. Comb generator is the ideal source for emission tests: Antenna Antenna Coupler LISN Coupler Wolfgang Müllner 37

38 System Checkout Procedure Primary reference measurement Regular check measurement and computation of the difference to the reference. If deviation is less than a threshold the setup is OK otherwise the cause needs to be investigated. Wolfgang Müllner 38

39 RefRad X: Comb Generator & Field Source 3 Unique Features: Generator is built into an antenna field source with calculable radiation performance Fibre Link for synchronization of generator and receiver 30 db more dynamic range Frequency range starts from 10 khz system check for LISNs Wolfgang Müllner 39

40 The Antenna Coupler Small dipole antenna Mechanically well defined positioning Close proximity to receive antenna Antenna Coupler Antenna Wolfgang Müllner 40

41 Setup RX-Antenna Antenna Coupler Anechoic Chamber EUT RefRad EMI-Receiver Computer Wolfgang Müllner 41

42 Deviation [db] System Check Results Defective Wing Dipole 1-30 Dipole 12 Broken Tip Frequency [MHz] Wolfgang Müllner 42

43 System Checkout Procedure for CE-Test Primary reference measurement Regular check measurement and computation of the difference If deviation is less than a threshold the setup is OK otherwise the cause needs to be investigated. Wolfgang Müllner 43

44 Voltage [dbµv] 2-Phase LISN Coupler EN B QP EN B AV MaxPeak Average Frequency [MHz] Wolfgang Müllner 44

45 Coaxial Output Power [dbm] RefRad X: Output Signals khz 1MHz 5 MHz Frequency [MHz] Wolfgang Müllner 45

46 Time and Frequency Domain 1.2 a A T Time Frequency Wolfgang Müllner 46

47 How to Measure the Comb Spectrum EMI Receiver Set: f_start, f_stop, f_step, RBW No control software required Spectrum Analyzer Set: span, RBW Control software sets f_center and reads marker ONLY the amplitude at the comb peaks is relevant!!! Wolfgang Müllner 47

48 Output Level [dbm] Measurement of Comb Spectrum Frequency [MHz] Wolfgang Müllner 48

49 Frequency Accuracy of Comb Generators Comb Generator: 1 MHz crystal with 50ppm accuracy 150 khz at 3 GHz EMI Receiver: RBW > 150 khz Spectrum Analyzer: RBW > 150 khz, zero span RBW <<, span > 150 khz good for low signal amplitude Wolfgang Müllner 49

50 Level [dbm] Error Caused by Frequency Offset (RBW <<) SPAN 300kHz SPAN 100kHz SPAN 20kHz SPAN 10kHz SPAN 0Hz Frequency [MHz] Wolfgang Müllner 50

51 RBW Considerations Large enough to measure the whole spectral energy of each pulse Small enough to measure only one pulse When changing the RBW within the suitable range the reading is nearly invariant Wolfgang Müllner 51

52 System Check Comb generator is a powerful measurement tool Special care on measurement settings of receiver bandwidth span amplitude RefRad X offers 3 unique advantages Generator is built into an antenna field source with calculable radiation performance Fibre Link for synchronization of generator and receiver 30 db more dynamic range Frequency range starts from 10 khz system check for LISNs Wolfgang Müllner 52

53 Thank you very much for your attention! Wolfgang Müllner 53

54 Wolfgang Müllner, Patrick Preiner, Alexander Kriz No part of this document may be copied by any means without written permission from SEIBERSDORF LABORATORIES Seibersdorf Labor GmbH, 2444 Seibersdorf, Austria T +43 (0) Wolfgang.Muellner@seibersdorf-laboratories.at