Calibration and Validation for Automotive EMC Wolfgang Müllner Patrick Preiner Alexander Kriz Seibersdorf Labor GmbH 2444 Seibersdorf, Austria http://rf.seibersdorf-laboratories.at rf@seibersdorf-laboratories.at
Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 2
ALSE Performance Validation Standard: CISPR 25 Frequency range: 150kHz 1GHz Two methods: reference measurement method modelled long wire method Wolfgang Müllner 3
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
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
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 20 14 15 10 75 points out of 481 exceed 6 db (= 15.59%) 12 10 8 42 points out of 481 exceed 6 db (= 8.73%) 5 6 0 4-5 2 0-10 -2-15 -4-6 -20 0 1 10 100 1000 Frequency [MHz] -8 0 1 10 100 1000 Frequency [MHz] Wolfgang Müllner 6
900 mm 1000 mm 900 mm 250mm Delta [db] 750 mm ALSE Performance Validation Results RMM: OUT OF SPEC!!! 20 RMM 15 10 5 75 points out of 481 exceed 6 db (= 15.59%) RX Monopole 1000 mm TX Monopole TX Monopole RX Ant. 1000 mm P3 P2 TX Ant. P1 0 100mm Test bench 100mm Test bench -5 1000 mm 1000 mm -10-15 Monopole Monopole test bench test bench -20 0 1 10 100 1000 Frequency [MHz] 100 mm 100 mm Wolfgang Müllner 7
ALSE Performance Validation Results RMM: OUT OF SPEC bonding is critical!!! Wolfgang Müllner 8
Delta [db] ALSE Performance Validation Results LWM: WITHIN SPEC!!! LWM 14 12 10 8 42 points out of 481 exceed 6 db (= 8.73%) 6 4 2 0-2 -4-6 -8 0 1 10 100 1000 Frequency [MHz] Wolfgang Müllner 9
Regular ALSE Re-Calibration Regular Re-Calibration of ALSE ALSE is test equipment Needs regular calibration (ISO 17025 requirement) Certain time interval (1-5 years) Anytime a change in the ALSE is made: Setup Table Bonding Antennas Absorbers Wolfgang Müllner 10
Delta [db] Regular ALSE Re-Calibration 10 8 6 LWM 4 2 0-2 -4-6 -8-10 39 points out of 481 exceed 6 db (= 8.11%) 34 points out of 481 exceed 6 db (= 7.07%) 0 1 10 100 1000 Frequency [MHz] Wolfgang Müllner 11
Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 12
Antenna Calibration Standard: SAE ARP 958 Determining the Antenna Factor (AF) OATS (d=1m; h=3m) (SAE ARP 958) Wolfgang Müllner 13
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 9.73 10 log (G) V T λ (SAE ARP 958) (SAE ARP 958) Wolfgang Müllner 14
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 24.46 + 0.5 (E max D + A 1 + A 2 A 3 ) AF 2 db = 10 log f M 24.46 + 0.5 (E max D + A 1 + A 3 A 2 ) AF 3 db = 10 log f M 24.46 + 0.5 ( E max D + A 2 + A 3 A 1 ) Wolfgang Müllner 15
Antenna Factor [db/m] Antenna Factor [db/m] Antenna Factor [db/m] Antenna Calibration (SAE ARP 958) 24 22 20 18 16 14 12 26 10 24 8 22 0 50 100 150 200 250 300 Frequency [MHz] Biconical antenna 20 18 49 16 44 14 39 12 200 300 400 500 600 700 800 900 1 000 Frequency [MHz] Log. Per. antenna 34 29 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Frequency [GHz] Horn antenna Wolfgang Müllner 16
Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 17
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
LISN - Defined Impedance? Impedance between conductor and reference earth Device: mains plug Automotive components: cable shoe or plug 19
LISN - Calibration Jig 20
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
LISN - Requirement of CISPR 16-1-2 Tolerance Absolute ± 20 % Phase ± 11.5 Ref. [1] 22
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
Impedance [ ] Different calibration jigs will lead to 100 80 Jig A Jig B Limit 60 40 20 0-20 10-1 10 0 10 1 10 2 Frequency [MHz] 24
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
Correction Circuit Formula Z VNA C L Z LISN 1 Z VNA = 1 jωc + jωl + Z LISN 26
Impedance [ ] Calibration plane: Cable shoe 100 80 60 Calibration plane cable shoe Jig A Jig B Jig A corrected Jig B corrected Limit 40 20 0-20 10-1 10 0 10 1 10 2 Frequency [MHz] 27
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
Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 29
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
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
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
Calibration Methods Methods deliver relatively low field strength Automotive Company standards require higher field strength: EMC-CS-2009.1 (Ford) STD 515-0003 (Volvo) GMW 3097 (GM) GS 95002-2_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
Reverberation Chamber (RC) SG Amp Power Meter Reverberation Chamber Read Out
Field Strength [V/m] Power [W] Reverberation Chamber (RC) 3500 70 Field Strength 3000 2500 Field Strength Limit Power 60 50 Achievable Field Strength: 2000 1500 40 30 1 4 GHz: 1200 V/m 1000 20 4 12 GHz: 600 V/m 500 0 1 10 10 0 12 18 GHz: 300 V/m Frequency [GHz]
Overview ALSE Performance Validation Antenna Calibration LISN Calibration Field Probe Calibration System Check Wolfgang Müllner 36
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
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
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
The Antenna Coupler Small dipole antenna Mechanically well defined positioning Close proximity to receive antenna Antenna Coupler Antenna Wolfgang Müllner 40
Setup RX-Antenna Antenna Coupler Anechoic Chamber EUT RefRad EMI-Receiver Computer Wolfgang Müllner 41
Deviation [db] System Check Results 20 10 0-10 -20 Defective Wing Dipole 1-30 Dipole 12 Broken Tip -40 10 100 1000 10000 Frequency [MHz] Wolfgang Müllner 42
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
Voltage [dbµv] 2-Phase LISN Coupler 90 80 70 60 50 EN 55022 B QP EN 55022 B AV 40 30 MaxPeak Average 20 0.1 1 10 100 Frequency [MHz] Wolfgang Müllner 44
Coaxial Output Power [dbm] RefRad X: Output Signals 10 0-10 -20-30 -40-50 -60-70 10 khz 1MHz 5 MHz -80 0.01 0.1 1 10 100 1000 10000 Frequency [MHz] Wolfgang Müllner 45
Time and Frequency Domain 1.2 a 1 1.2 A 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 T Time 0 5 10 15 20 25 30 35 40 45 0 0 1 2 3 4 5 6 7 8 9 Frequency Wolfgang Müllner 46
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
Output Level [dbm] Measurement of Comb Spectrum -10-20 -30-40 -50-60 -70-80 -90 40 41 42 43 44 45 46 47 48 49 50 Frequency [MHz] Wolfgang Müllner 48
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
Level [dbm] Error Caused by Frequency Offset (RBW <<) -10-20 -30-40 -50-60 SPAN 300kHz SPAN 100kHz SPAN 20kHz SPAN 10kHz SPAN 0Hz -70 1 10 100 1000 10000 100000 Frequency [MHz] Wolfgang Müllner 50
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
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
Thank you very much for your attention! Wolfgang Müllner 53
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) 50 550-2803 Wolfgang.Muellner@seibersdorf-laboratories.at www.seibersdorf-rf.com