1. The Ongoing Challenges in
Automotive EMC Compliance
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2. The Ongoing Challenges in
Automotive EMC Compliance
Contents
Introduction ..............................................................................................2
History .......................................................................................................3
The Changing EMC Environment.............................................................3
Changing EMC Test Requirements ..........................................................6
Summary ...................................................................................................7
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3. The Ongoing Challenges in
Automotive EMC Compliance
Introduction
With advances in technology over the last decade, customer demand and OEM
competition has forced automakers to try to integrate many of the latest
technologies into their vehicles. Many of these technological advances, whether
entertainment, communication or performance improvements, do succeed in
bringing to the consumer a new level of comfort and convenience as well as
enhanced safety features. But along with these features come new challenges to
ensure EMC (Electromagnetic Compatibility) and device interoperability within the
vehicle. EMC issues can result in minor annoyances such as unwanted noise through
the entertainment system, as well as major issues such as loss of engine functions or
control issues that could compromise the safety of drivers, passengers and the
public. Add to this the growing demand of Hybrid Electric Vehicles (HEV) and
Electric Vehicles (EV). These systems may bring a whole new set of concerns in
relation to EMC. For these reasons, EMC is and will continue to be a very important
topic of concern for the automakers’ present and future.
There are two opposing forces at work influencing EMC in the vehicular
environment. 1) The growing number of electronic components and modules for
control, communications, and entertainment now being installed make achieving
EMC far more demanding. 2) The force promising to bring the situation under
control is the trend to replace complex vehicle wiring carrying analog, digital, and
high-current signals with simpler, low-power signaling protocols.
Between these two forces, engineers are modifying their predictive tools to keep up
with changes at all levels – integrated circuit EMC evaluation, module EMC
prediction and measurement, and whole vehicle characterization. As circuits operate
at higher frequencies (and voltages), simulation methods have to adopt smaller
grids for the accurate prediction of the resulting electromagnetic fields.
As this process of modification is underway, the vehicle manufacturers need to
assure that new modules have been tested to their respective EMC standards
correctly and that the standards reflect the actual environment of future installation.
While many vehicle EMC standards are non-governmental (and/or OEM specific)
and therefore simpler to update, in the EU the Automotive EMC Directive
2004/104/EC contains its own requirements and is therefore more cumbersome to
amend. Fortunately, it contains a number of international EMC standard references.
With the recent surge of public awareness for a need for alternative vehicles such as
EV’s and HEV’s , there are more independent auto manufacturers on the scene and
they are starting to review their own EMC procedures and may see themselves
developing their own standards based on their findings and business growth.
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4. The Ongoing Challenges in
Automotive EMC Compliance
History
The popularization of the car radio in the late 1920s was the “canary in the coal
mine” — the proverbial early warning— that automotive EMC would be an
ongoing challenge. By the 1930s, a number of commercial radio brands were
available. The early models were AM (amplitude modulation) only and very
susceptible to both ignition noise and static buildup from the car’s tires. Both
sources of disturbances were quickly overcome. Spark plug suppression was
provided by resistive cables and resistive plugs; research on optimum spark plug
suppression continued into the 1970s1. Conductive carbon was added to the car
tires to prevent electrostatic charge buildup. In 1947, SAE J551, the first SAE
(Society of Automotive Engineers) EMC standard, was published, but it was not
until the proliferation of vehicular electronics in the 1970s that development of
further vehicle EMC standards occurred.
The Changing EMC Environment
Today’s motor car contains an amalgam of legacy electrical/electronic functions and
more recent devices – literally dozens of components or modules, sensors and
actuators, and more than one network. Table 1 below lists typical functions and
their attributes.
function history attributes
Airbag deployment Existing Critical
Braking control Existing Critical
Comfort, Radio Noise, gage/warning
Cabin environment Existing
function
Collision avoidance New Likely unlicensed radar 77 GHz.
Communications
New Cellular, Bluetooth (800, 1900, 2400 GHz)
system
Environmental and legal concerns in some
Emissions control Existing
states
Engine ignition Existing Critical
May include satellite radio receiver, FM
Entertainment system New
modulator (low power 88-108 MHz).
Fuel injection Existing Critical
1
“Relationship Between Spark Plugs and Engine-Radiated Electromagnetic Interference,” IEEE
Transactions on Electromagnetic Compatibility, Burgett et. al.,August 1974, pp. 160-172.
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5. The Ongoing Challenges in
Automotive EMC Compliance
Lighting system New Some Xenon discharge lamps.
Navigation system New GPS receiver
Noise cancellation New Comfort
Seat and pedal position Existing Critical
Short-range and Part 90 radio (170-300
Security system Existing
MHz)
Stability control New Critical
Tire pressure
New Short-range radio
monitoring
Transmission control Existing Critical
Table 1 Typical automotive electronic component or module functions.
Each of these functions exists in, and impacts, the vehicle’s EMC environment. For
example, all of the control systems add to network/bus noise. Also, the
communications, entertainment and security systems introduce radio sources while
the GPS (global positioning systems) and satellite radio receivers require very low RF
noise over their operating bands.
Compounding these EMC challenges from the added electronic functions are the
new factors associated with Hybrid Electric Vehicles (HEVs) and Electric Vehicles
(EVs). Specifically, these include bus voltages exceeding 200 V, power inverter
switching noise, and new bus/cable configurations. These issues are illustrated in
the propulsion system block diagrams in Figure 1 and 2 for HEV and EV
configurations.
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6. The Ongoing Challenges in
Automotive EMC Compliance
transmission
DC
AC
power High
inverter voltage
battery
DC/DC 12V battery
Electric motor Engine
Figure 1 Simplified HEV (Hybrid Electric Vehicle) block diagram.
DC
Electronic High
control voltage
unit battery
12V battery
Power inverters and motors
Figure 2 Simplified EV (Electric Vehicle) block diagram.
In addition to the basics shown in these figures, there are the myriad modules,
sensors, actuators, networks, and central control for the vehicle.
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7. The Ongoing Challenges in
Automotive EMC Compliance
Changing EMC Test Requirements
Existing EMC whole vehicle and module test standards cover the range of
electromagnetic phenomena in conventional vehicles2. Vehicle manufacturers have
adopted SAE and international standards to varying degrees and have established
their own EMC standards that the testing laboratory must follow closely. Table 2
summarizes some of the relevant standards by reference number.
A sample of automotive EMC standards
parameter SAE GM Ford Toyota Int’l
EMISSIONS
CISPR TSC7026G
25 TSC7058G
Radiated RF ES-XW2T- CISPR 25
J551/1,
GMW3097 1A278-AC
J551/5
Conducted RF CISPR 25 TSC7058G CISPR 25
CS-2009.1
Conducted J1113-42 _ ISO7637-2
transient
RADIATED IMMUNITY
J551/1, TSC7025G
J551/12, ES-XW2T- ISO 11452-2,
RF immunity
J551/16, GMW3097 1A278-AC ISO 11452-3
J1113/28
Magnetic field J551/17 CS-2009.1 TSC7001G
immunity ISO 11452-8
J1113-22
COUPLED TRANSIENTS
Inductive J1113-12 ES-XW2T- TSC7001G
coupled 1A278-AC
transients GMW3097 ISO 7637-2
CS-2009.1
CONDUCTED IMMUNITY
Susceptibility J551/13 TSC7315G ISO 11452-4
J1113-2,3,4 ES-XW2T-
J1113-11 GMW3097 1A278-AC TSC7001G ISO 7637-2,
Transient
ISO 7637-3
ESD J551/15 CS-2009.1 TSC7018G ISO 10605
J1113-13
2
“An Overview of Automotive EMC Standards, “Poul Anderson, IEEE EMC Symposium 2006 Proceedings, 2006,
pp. 812-816.
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8. The Ongoing Challenges in
Automotive EMC Compliance
Due to the high cost of performing whole-vehicle EMC testing and the need to
expedite component integration, EMC testing is being performed at both the
component or module and chip levels. The results are then used to predict
compliance of the whole vehicle. Even without the added complexities of new HEV
and EV propulsion systems, there are difficulties inherent in the existing test
methods. At the chip or IC level, test standards such as IEC 61967-x family and SAE
J145 2/3 do not fully predict installed EMC. The correlation between near- and far-
field emissions may not hold, and the result is highly dependent on any external
wiring harness. Also, at the module or component level, similar ambiguities exist.
Component testing, however, can still be useful for identifying potential EMC
problems.
The introduction of HEV and EV propulsion systems clearly intensifies the challenges
to existing test methods even more. High battery voltages reduce power
transmission losses, but the resulting higher system impedances can render invalid
emissions test results obtained with the artificial networks described in CISPR 253.
Battery and drive motor impedance and impedance changes can also become an
important factor in EMC. Worst-case RF emissions from vehicular power converters
have been observed under transient conditions of load and speed4. Unfortunately,
measurement standards have not yet taken this observation into account.
Summary
The automotive EMC environment is in a constant state of flux as new onboard
electric devices, communications media (both wired and wireless), and new drive
systems are added. Consequently, both EMC standards writers and vendors find
themselves in a situation without fixed, agreed-upon testing procedures for assuring
the compatibility of vehicles and components in hybrid and all electric cars.
Ongoing change is the only constant. Automakers need to continue with strict
attention to detail and try to model tests to capture the newer issues and concerns
they come across. Component suppliers need to be aware of these concerns during
their development cycles. Manufacturers of after market products and “cross over”
devices, such as various kinds of IT equipment now being used in vehicles need to
be cognizant of the requirements of the automotive EMC environments.
Although automotive EMC standards are well-established by manufacturers and
both domestic and international standards-making bodies, refinements may be
3
“High Voltage Automotive EMC Component Measurements Using an Artificial Network,” Nelson et. al.,IEEE
Proceedings 18th Int. Zurich Symposium on EMC, 2007, pp. 195-200.
4
“HEV System EMC Investigation during Transient Operations,” Nelson and Aidam, IEEE Proceedings 18th Int.
Zurich Symposium on EMC, 2007, pp. 205-208.
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9. The Ongoing Challenges in
Automotive EMC Compliance
needed to achieve better correlation between chip-level and component- or
module-level measurements and whole vehicle testing. New HEV and EV drive
systems continue to add further challenge to automotive EMC testing.
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