RF Ingress MEasurements for STP Cables from from Automotive ALSE Test ... Direct measurement of RF ingress voltage at cable ... RF Ingress MEasurements for STP Cables from Automotive ALSE ...

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  • RF Ingress Measurements for STP Cables from Automotive ALSE Test

    Larry CohenRamin Shirani

    11/8/2017

  • 11/8/2017

    Overview Measurement of the differential RF ingress voltage induced at the termination of an

    automotive shielded cable (STP) based on standard automotive radiated immunity absorber-lined shielded enclosure (ALSE) test method described in ISO 11452-2

    Test results from 80 MHz to 1 GHz and 1GHz to 3GHz

    Direct measurement of RF ingress voltage at cable terminations; no PHY MDI port interface

    Results are for differential rms voltage vs frequency at cable termination (100 Ohms differential impedance)

    Test performed on STP with H-MTD connectors and STP with HSD connectors; both cable assemblies were 2 meters long with only end connectors

    2

  • 11/8/2017

    3 ALSE Automotive Cable RF Ingress Measurement Test Setup

    Ground plane table(90 cm above ground

    plane floor)

    1 m

    1.5 m

    DUT cable harness, totallength < 2 meters

    Balun

    Antenna height is 1mabove ground plane floor

    Absorber-linedshielded chamber

    (ALSE)

    Insulating cable support(5 cm thick)

    GPIBControl PC

    Shielded TerminationBlock

    (Sits on 5 cm ofinsulating material)

    0.1 m

    Shielded enclosurefor cable adapter

    (Sits on 5 cm ofinsulating material)

    CableAdapter

    >1.5 m

    Cableconnector

    GPIB

    RF Power Amplifier

    RF SignalGenerator50 50

    GPIB GPIB

    50

    Ferriteclamp

    INOUT

    50

    DirectionalCoupler (40 dB)

    FWDCPL

    SpectrumAnalyzer / RFPower Meter

    50

    EMC Lab GPIBControl PC for

    ALSE TestGPI

    B

    The spectrum analyzer and directional coupler are used to monitorthe forward signal power to the antenna. At each frequency, thesignal generator output is adjusted to match the forward signalpower previously obtained during the calibration procedure.

    R&S FSU-8SpectrumAnalyzer

    (8 GHz BW)

    GPIB

    Balun

    GPIB

    Ferriteclamp

    50

    Aquantia testequipment

    EMC lab testequipment

    24 ft. coaxialcable

    ETSPI-102

    Added 3 dBattenuators toimprove differentialport return loss

    -3dB

    -3dB

    0.2 m

    0.2 m 61 61

    Split-ring

    ferriteclamps(on 6"coax)

    Split-ringferrite

    clamps

    Horn antenna aligned 10 cmoffset from DUT for testingfrom 1 GHz to 3 GHz

    Test field strength is 50 V/mfrom 80 MHz to 3 GHz (CW).

    Measured result scaled to100 V/m by adding 6 dB.

    Bilog antenna aligned tomidpoint of cable span fortesting from 80 MHz to 1 GHz

    Balun

    The spectrum analyzerdetermines both the frequencyand power of the RF ingresssignal by monitoring themaximum peak signal (RFingress from the radiation) duringeach frequency sweep.

    31 31

    61 31

    Cable adapter breaks out STP andSSQ 100 differential cablechannels to a pair of 50 SMA jacks

    Split-ring ferrite clamps added to allcoaxial cables inside chamber tosuppress stray test fixture RFingress below 1 GHz and lower themeasurement noise floor.

    Shielded enclosure has added coppertape on seams and EMI gaskets to

    reduce stray ingress above 500 MHz

    >2 m

    3

  • 11/8/2017

    4 ALSE Automotive Cable RF Ingress Measurement Test Setup (80 MHz to 1 GHz)

    Antenna

    Shielded Cable (DUT)

    Shielded Cable Adapter

    24 ft Coaxial Cable

    Copper Ground Plane Table

    ETS PI-102

    Shielded Termination Block

    Split-ring Ferrite Clamps

    4

  • 11/8/2017

    5 Test Setup Measurement noise floor is the measured stray RF ingress from the stand-alone test fixture

    Measured under ALSE test conditions with the cable DUT disconnected from the cable adapter and all unconnected cable ports on the test fixture covered with copper tape

    Cable adapter enclosures have EMI gasket seals between the cable connectors and enclosure and copper tape on seams to reduce stray ingress above 500 MHz

    Added split-ring ferrite clamps to the exposed coaxial cables inside the chamber to reduce stray ingress coupling below 500 MHz; moderately effective below 200 MHz

    Spectrum analyzer operated in free running sweep mode; measures both frequency and level of maximum peak signal during each frequency sweep

    Proper measurement requires a spectrum analyzer measurement noise floor < -150 dBm/Hz to observe weak ingress signals, otherwise an additional pre-amplifier is necessary

    RF disturber field calibrated to 50 V/meter using a CW signal (no 80% AM)

    Reduced field strength to minimize harmonic distortion from the EMC lab RF amplifier

    Harmonic distortion can introduce measurement errors for this test setup by causing the spectrum analyzer to observe the wrong (harmonic) peak

    Test level a compromise between harmonic distortion and improved signal observability

    Used linear spaced frequency sweep step size(s) from ISO 11452-1 Table 2; dwell time set at 2 sec.5

  • 11/8/2017

    6

    Port 2(Cable Adapter)100 Differential

    Port 1(Spectrum Analyzer)50 Single-ended

    ETSPI-102(Balun)

    -3dB

    -3dB

    24 ft. Coaxial cable6 in Coaxial cables

    ALSE Test Fixture

    6

  • 11/8/2017

    7

    7

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    8

    8

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    9

    9

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    10

    10

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    11

    Observations and Next Steps Overall, the RF ingress in the STP cable with the H-MTD connectors was lower than the STP cable with the

    HSD connectors

    The peak RF ingress in the STP cable with the H-MTD connectors (~1.5 mV rms) was lower than STPcable with the HSD connectors (~5 mV rms) over 80MHz to 1GHz

    The peak RF ingress in the STP cable with the H-MTD connectors (~3 mV rms) was lower than the level in the STP cable with the HSD connectors (~6 mV rms) over 1 GHz to 3 GHz

    There is a measurement discontinuity at 1 GHz because of the change in relative antenna position with the (slightly) different test setups for measurements above and below 1 GHz

    RF ingress measurements below 200 MHz may not be accurate because of a higher measurement noise floor from stray RF ingress into the test fixture cabling

    Some reduction in the measurement noise floor below 200 MHz obtained by adding split-ring ferrite clamps to the exposed coaxial cables inside the chamber

    Passing the 24 ft coaxial cable outside the chamber through a bulkhead connector at the chamber wall instead of a shielded aperture should provide some additional improvement

    Next steps Extend measurements to 5 GHz; insertion loss notches reported in this range (possibly caused by helical

    shield construction) may have important implications for radiated immunity

    Test on different cable types (e.g. SSQ) and cable spans with connector junctions

    Test on cable bundles 11

    RF Ingress Measurements for STP Cables from Automotive ALSE TestOverviewALSE Automotive Cable RF Ingress Measurement Test SetupALSE Automotive Cable RF Ingress Measurement Test Setup (80 MHz to 1 GHz)Test Setup Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Observations and Next Steps

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