automotive datalinks over twisted quad cabling - … · thomas müller 2 outline ieee rtpge...
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IEEE RTPGE
Rosenberger Hochfrequenztechnik GmbH & Co. KG
Automotive Datalinks over Twisted Quad Cabling
T. Müller, G. Armbrecht, S. Kunz
Thomas Müller 2
IEEE RTPGEOutline
� Automotive Datalinks over Twisted Quad Cabling� Twisted Quad fundamentals� Twisted Quad connector interface
� EMC� Coupling to adjacent systems
� Measuring EMC properties of components
� Linking mode conversion to radiation
� Summary
Thomas Müller 3
IEEE RTPGETwisted Quad Fundamentals
� Opposite conductors form a differential pair� Fields cancel each other > virtual ground plane� Independent transmission of two data streams over one cable� Second pair can also be used for remote powering devices� Compact size� Round shape without fillers (mechanically stable)
+-
+ -
Virt. GND Pair 1 Virt. GND Pair 2
Thomas Müller 4
IEEE RTPGETwisted Quad Fundamentals
� Typical insertion loss 1 dB/m @ 1 GHz� Low crosstalk� Bidirektional communication
up to 3 GBit/s over 10 m LVDS possible
Sdd21 [Pair 1]
f [MHz]
Inse
rtio
n lo
ss [
dB/m
]
0.1 1 10 100 10000.001
0.01
0.1
1
10
NEXT [Pair 1 to Pair 2]
f [MHz]
Sdd
21 (
near
-end
) [d
B]
0.1 1 10 100 1000-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Orange: Cat 6aBlack: Cat 5
Thomas Müller 5
IEEE RTPGE
� Open interface (connectors are available from different vendors)
� Interface as described in automotiveIEEE 1394 Copper Automotive Standard(Supplement to IDB-1394) Project TS2008001
� Designed to meet automotive requirements� Electrical (e.g. ISO/IEC 60603-7-51 CAT 6a, LV213)
� Mechanical and environmental (forces, waterproofness, LV214, USCar)
� Fully automated assembly process
� EMC� Radial shielding contact
� Compatible with fully-shielded (braid + foil),semi-shielded (foil) and unshielded
STQ Connector Interface
Thomas Müller 6
IEEE RTPGEEMC – Coupling to adjacent systems
Ethernet Networking100Base-TX,BroadR-Reach
CommunicationGSM, UMTS, LTE,WLAN, Bluetooth,Car2X, …
BroadcastAM, FM, DVB-T,DAB(+)
TransientsElectronic enginecontrol, switchingpower supplies,processor clock
Video Linksup to 3Gbit/sAPIX, LVDS, MHL
HV-Traction networkElectric drives,auxiliary systems(48V-Powernet)
EMCNavigationGPS, Glonass,Galileo
BUS SystemsLIN, CAN, MOST,USB
Thomas Müller 7
IEEE RTPGE
Common to differential mode conversion
Differential mode signal behavior
Differential to common mode conversion
Common mode signal behavior
Differential In
SCD11SCD11 SCD12SCD12
SCD21SCD21 SCD22SCD22
SDC11SDC11 SDC12SDC12
SDC21SDC21 SDC22SDC22
SCC11SCC11 SCC12SCC12
SCC21SCC21
SDD11SDD11
SCC22SCC22
Port2Port1
Common In
Port2Port1
Diff
eren
tial O
ut
Por
t2P
ort1
Com
mon
Out
Por
t2P
ort1
SDD12SDD12
SDD22SDD22SDD21SDD21
Common to differential mode conversion
Common to differential mode conversion
Differential mode signal behaviorDifferential mode signal behavior
Differential to common mode conversion
Differential to common mode conversion
Common mode signal behaviorCommon mode signal behavior
Differential InDifferential In
SCD11SCD11 SCD12SCD12
SCD21SCD21 SCD22SCD22
SDC11SDC11 SDC12SDC12
SDC21SDC21 SDC22SDC22
SCC11SCC11 SCC12SCC12
SCC21SCC21
SDD11SDD11
SCC22SCC22
Port2Port2Port1Port1
Common InCommon In
Port2Port2Port1Port1
Diff
eren
tial O
utD
iffer
entia
l Out
Por
t2P
ort2
Por
t1P
ort1
Com
mon
Out
Com
mon
Out
Por
t2P
ort2
Por
t1P
ort1
SDD12SDD12
SDD22SDD22SDD21SDD21
Measuring EMC properties
� Coupling attenuation determines the EMC properties of a differential channel as the sum of� Differential to common mode conversion attenuation
� Shielding attenuation for screened cables
� Mode conversion measured withS-parameter measurements byNetwork Analyzer (NWA)� TCL (Sdc11)� TCTL (Sdc21)
� …
Thomas Müller 8
IEEE RTPGEMeasuring EMC properties
� Unbalance along the channel causesmode conversion
� Concentrated unbalance can be compensated(e.g. through optimized footprint design)
� Distributed unbalance is most critical(e.g. within cable)
0.1 1 10 100 1000-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0Length imbalance of differential pair
f [MHz]
Equ
al L
evel
Tra
nsve
rse
Con
vers
ion
Tra
nsfe
r Lo
ss [
dB]
∆∆∆∆ l = 500 mm
∆∆∆∆ l = 200 mm
∆∆∆∆ l = 100 mm∆∆∆∆ l = 50 mm
∆∆∆∆ l = 20 mm∆∆∆∆ l = 10 mm
CAT 5/6a Limit
∆∆∆∆ l = 1 mm
0.1 1 10 100 1000-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0Capacitance imbalance of differential pair
f [MHz]
Equ
al L
evel
Tra
nsve
rse
Con
vers
ion
Tra
nsfe
r Lo
ss [
dB]
CAT 5/6a Limit
∆∆∆∆ C = 0.1 pF
∆∆∆∆ C = 100 pF∆∆∆∆ C = 50 pF
∆∆∆∆ C = 20 pF∆∆∆∆ C = 10 pF∆∆∆∆ C = 5 pF
∆∆∆∆ C = 1 pF
∆∆∆∆ C = 2 pF
Thomas Müller 9
IEEE RTPGE
� Measure transmission path� Identify basic screening parameters
Measuring EMC properties
EMI Source
EMI-EMS Trans-
mission Path
EMIVictim
Interferencetransfer function
Operational system
Adjacent systemsubject to interference
Transmitter
(e.g. NWA Port1)
Transfer impedancescreening-/ coupling
attenuation
Receiver
(e.g. NWA Port2)
Thomas Müller 10
IEEE RTPGE
� Triaxial tube allows measuring screening properties of individualcomponents along the channel
Measuring EMC properties
Cable Inline connections Feed-throughs
Thomas Müller 11
IEEE RTPGE
� Allows measuring screening properties of individual components along the channel by means of triaxial measurements
� The DUT can be fed from the NWA in common mode or differential mode to measure screening- or coupling attenuation
� Also applicable for unshielded differential pairs
Measuring EMC properties
DUT Triaxial Tube Diff. / comm. Termination
Shielded ferrule
NWA
Coax toDifferential PCB
1
2
3
Thomas Müller 12
IEEE RTPGE
� Twisted Quad cable assembly measurement examples
� Measurement of screening attenuation not intended for unshieldedcables according to given standards
� Quality of shield may be adjusted by construction
Measuring EMC properties
0.1 1 10 100 1000 10000-120
-100
-80
-60
-40
-20
0
Frequency [MHz]
Scr
eeni
ng a
tten
uatio
n [d
B]
Semi-shieldedFully-shieldedUnshielded
Screening attenuation
Thomas Müller 13
IEEE RTPGE
� Twisted Quad cable assembly measurement examples
� Fully-shielded cables provide excellent coupling attenuation� Unshielded cables can provide noticeable performance, if the balance
throughout the channel is maintained (connector, cable, termination)� Semi-shielded cables may be a viable compromise
Measuring EMC properties
0.1 1 10 100 1000 10000-120
-100
-80
-60
-40
-20
0
Frequency [MHz]
Cou
plin
g at
tenu
atio
n [d
B]
Coupling attenuation
Semi-shieldedFully-shieldedUnshielded
Coupling attenuation
Thomas Müller 14
IEEE RTPGE
� Measure differentialand common modecoupling to striplinein a three port NWAmeasurement
� UTQ cable 1.7 m� First end connected
to ground plane� Second end floating
� Measure TCTL inin same setup
� Compare the resultswith triaxial tube
EMC – Linking mode conversion to radiation
1 2 3 4
DUT 1.7 m
NWA
floating 1 2 3 4grounded
Thomas Müller 15
IEEE RTPGEEMC – Linking mode conversion to radiation
� Small coupling at low frequencies due to limited coupling length� Resonances at quarter wavelength and odd multiples
100
101
102
103-120
-100
-80
-60
-40
-20
0
f [MHz]
com. mode coupling diff. mode coupling
Thomas Müller 16
IEEE RTPGEEMC – Linking mode conversion to radiation
� Coupling to stripline is linked to mode conversion properties of the DUT� Mode conversion as difference between differential and common mode
coupling can be reproduced� Triaxial tube is less dependent on setup (e.g. DUT length, coupling
length, grounding) and easier to handle (e.g. no need for shielded chamber)
100
101
102
103-80
-70
-60
-50
-40
-30
-20
-10
0
f [MHz]
TCTLStripline: diff. coupling - com. coupling Triaxial Tube: coupling attenuation - screening attenuation
Thomas Müller 17
IEEE RTPGESummary
� Twisted Quad cables are widely used for differential signal transmission within vehicles.
� In combination with the STQ connector interface the automotive requirements concerning mechanical and electrical properties are met.
� The EMC properties of components along the channel can be evaluated by measuring mode conversion and coupling attenuation by means of a triaxial tube.
� The grade of shielding may be adapted to bandwidth, topology andEMC-environment of the application to be implemented without the need to change the connector interface.
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