ISO 11451-1:2025

International
Standard
ISO 11451-1
Fifth edition
Road vehicles — Vehicle test
2025-06
methods for electrical disturbances
from narrowband radiated
electromagnetic energy —
Part 1:
General principles and terminology
Véhicules routiers — Méthodes d'essai d'un véhicule soumis
à des perturbations électriques par rayonnement d'énergie
électromagnétique en bande étroite —
Partie 1: Principes généraux et terminologie
Reference number
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General aim and practical use . 6
5 General test conditions . 7
5.1 General .7
5.2 Test temperature .7
5.3 Supply voltage .8
5.3.1 Vehicle low voltage (LV) power supply .8
5.3.2 Hybrid or electric vehicle not connected to power mains .8
5.3.3 Hybrid or electric vehicle in charging mode (a.c. or d.c.) .8
5.4 Modulation .8
5.5 Dwell time .9
5.6 Frequency step sizes .9
5.7 Definition of test severity levels .10
5.8 Evaluation of test instrumentation uncertainties .10
6 Instrumentation . 10
6.1 DC-charging-AN, AMN, and AAN .10
6.2 Test signal quality .10
7 Test procedure .10
7.1 Test plan .10
7.2 Test methods .11
7.2.1 General .11
7.2.2 Substitution.11
7.2.3 Closed loop levelling . 12
7.2.4 Disturbance application process . . 12
7.3 Test report . 13
Annex A (normative) Function performance status classification (FPSC) . 14
Annex B (normative) Direct current charging artificial networks (DC-charging-AN), artificial
mains networks (AMN) and asymmetric artificial networks (AAN) . 17
Annex C (normative) Constant peak test level for amplitude modulation .24
Annex D (informative) Broadband test signal generation .27
Annex E (informative) Evaluation of test instrumentation uncertainties .36
Bibliography .39

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 32,
Electrical and electronic components and general system aspects.
This fifth edition cancels and replaces the fourth edition (ISO 11451-1:2015), which has been technically
revised.
The main changes are as follows:
— update in Table 1;
— update on modulations (type and frequency range);
— technical revision of Annex B;
— new Annex D on broadband test signal generation;
— new Annex E on evaluation of test instrumentation uncertainties.
A list of all parts in the ISO 11451 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
In recent years, an increasing number of electronic devices for controlling, monitoring and displaying a
variety of functions have been introduced into vehicle designs. It is necessary to consider the electrical and
electromagnetic environment in which these devices operate.
Electrical and radio-frequency (RF) disturbances occur during the normal operation of many items of motor
vehicle equipment. They are generated over a wide frequency range with various electrical characteristics
and can be distributed to on-board electronic devices and systems by conduction, radiation or both.
Narrowband signals generated from sources on or off the vehicle can also be coupled into the electrical
and electronic system, affecting the normal performance of electronic devices. Such sources of narrowband
electromagnetic disturbances include mobile radios and broadcast transmitters.
The characteristics of the immunity of a vehicle to radiated disturbances should be established. The
ISO 11451 series provides various test methods for the evaluation of vehicle immunity characteristics (not
all methods need be used to test a vehicle).
The ISO 11451 series is not intended as a product specification and cannot function as one (see A.1).
Therefore, no specific values for the test severity level are given.
It is important to consider protection from potential disturbances in a total system validation, and this can
be achieved using the various parts of the ISO 11451 series.
NOTE Immunity measurements of complete vehicles are generally able to be carried out only by the vehicle
manufacturer, owing to, for example, high costs of absorber-lined shielded enclosures, the desire to preserve the
secrecy of prototypes or a large number of different vehicle models. The ISO 11452 series specifies test methods for
the analysis of component immunity, which are better suited for supplier use.

v
International Standard ISO 11451-1:2025(en)
Road vehicles — Vehicle test methods for electrical
disturbances from narrowband radiated electromagnetic
energy —
Part 1:
General principles and terminology
1 Scope
This document specifies general conditions, defines terms, gives practical guidelines and establishes the
basic principles of the vehicle tests used in the ISO 11451 series, for determining the immunity of passenger
cars and commercial vehicles to electrical disturbances from narrowband radiated electromagnetic energy,
regardless of the vehicle propulsion system (e.g. spark-ignition engine, diesel engine, electric motor).
The electromagnetic disturbances considered are limited to continuous narrowband electromagnetic fields.
A wide frequency range (0,01 MHz to 18 000 MHz) is allowed for the immunity testing in the ISO 11451 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
CISPR 16-1-2:2014+AMD1:2017 CSV, Specification for radio disturbance and immunity measuring apparatus
and methods — Part 1-2: Radio disturbance and immunity measuring apparatus — Coupling devices for
conducted disturbance measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
1 dB compression point
input signal level at which a system becomes non-linear, when the output value will deviate by 1 dB of the
value given by an ideal linear system
3.2
absorber-lined shielded enclosure
ALSE
shielded enclosure (3.34) with radio frequency (RF) absorbing material on its internal ceiling and walls
Note 1 to entry: The common practice is for the room to have a metallic floor, but absorbing material can also be used
on the floor.
3.3
amplitude modulation
AM
process by which the amplitude of a carrier wave is varied following a specified law, resulting in an AM signal
3.4
artificial mains network
AMN
network that provides a defined impedance to the vehicle under test at radio frequencies (RFs), couples the
disturbance voltage to the measuring receiver, and decouples the test circuit from the supply mains
Note 1 to entry: There are two basic types of AMN, the V-network (V-AMN) which couples the unsymmetrical
voltages and the delta-network which couples the symmetric and the asymmetric voltages separately. The terms line
impedance stabilization network (LISN) and V-AMN are used.
Note 2 to entry: This network is inserted in the power mains of the vehicle in charging mode and provides, in a given
frequency range, a specified load impedance and which isolates the vehicle from the power mains in that frequency range.
3.5
artificial network
AN
network inserted in the supply lead or signal/load lead of apparatus to be tested which provides, in a given
frequency range, a specified load impedance for the measurement of disturbance voltages and which can
isolate the apparatus from the supply or signal sources/loads in that frequency range
Note 1 to entry: This network is inserted in the DC power lines of the vehicle in charging mode and provides, in a
given frequency range, a specified load impedance and which isolates the vehicle from the DC power supply in that
frequency range.
3.6
asymmetric artificial network
AAN
network used to measure (or inject) asymmetric (common mode) voltages on unshielded symmetric signal
(e.g. telecommunication) lines while rejecting the symmetric (differential mode) signal
Note 1 to entry: This network is inserted in the communication/signal lines of the vehicle in charging mode to provide
a specific load impedance and/or a decoupling (e.g. between communication/signal lines and power mains).
3.7
auxiliary equipment
AE
equipment needed to exercise, monitor or both exercise and monitor the operation of the vehicle
EXAMPLE Load simulator, charging cables, monitoring equipment, fibre optic interface modules, TV camera.
3.8
bonded
grounding connection with a DC resistance not exceeding 2,5 mΩ
and that provides the lowest possible impedance (resistance and inductance) connection between two
metallic parts
Note 1 to entry: See CISPR 16-2-1:2014/AMD1:2017, 5.3.
Note 2 to entry: A low current (≤100 mA) 4-wire milliohm meter is recommended for this measurement.
3.9
broadband signal
signal where the power is distributed over several megahertz, either by a broadband nature of the signal
itself or by a collection of subcarriers
3.10
bulk current
total amount of common mode current in a harness

3.11
charging mode
mode of operation intended for charging the storage system that provides electric energy for electric
propulsion
3.11.1
charging mode 1
charging mode where the vehicle is connected to a standard socket-outlet of an AC supply network, utilizing
a cable and plug, both of which are not fitted with any supplementary pilot or auxiliary contacts
Note 1 to entry: In some countries, mode 1 charging can be prohibited or requires special precautions.
Note 2 to entry: Charging mode 1 is defined in IEC 61851-1:2017, 6.2.1.
3.11.2
charging mode 2
charging mode where the vehicle is connected to AC mains using a charging cable, which has an electric
vehicle supply equipment (EVSE) (3.18) box in-line (e.g. in-cable control box / in-cable control and protection
device), providing control pilot signalling between the vehicle and the EVSE box and personal protection
against electric shock
Note 1 to entry: In some countries, special restrictions have to be applied for mode 2 charging.
Note 2 to entry: There is no communication with the vehicle.
Note 3 to entry: Charging mode 2 is defined in IEC 61851-1:2017, 6.2.2.
3.11.3
charging mode 3
charging mode where the vehicle is connected to a fixed installation [electric vehicle supply equipment (EVSE)
(3.18), e.g. AC charging station, AC wallbox] providing AC power to the vehicle, with communication between
the vehicle and the EVSE (through signal/control lines and/or through wired network lines)
Note 1 to entry: Charging mode 3 is defined in IEC 61851-1:2017, 6.2.3.
3.11.4
charging mode 4
charging mode where the vehicle is connected to a fixed installation [electric vehicle supply equipment
(EVSE) (3.18), e.g. DC charging station], providing DC power to the vehicle (with an off-board charger),
with communication between the vehicle and the EVSE (through signal/control lines and/or through wired
network lines)
Note 1 to entry: Charging mode 4 is defined in IEC 61851-1:2017, 6.2.4.
3.12
coupling
means or device for transferring power between systems
3.13
current injection probe
device for injecting current in a conductor without interrupting the conductor and without introducing
significant impedance into the associated circuits
3.14
current measuring probe
device for measuring the current in a conductor without interrupting the conductor and without introducing
significant impedance into the associated circuits

3.15
degradation of performance
undesired departure in the operational performance of any device, equipment, or system from its intended
performance
Note 1 to entry: The term “degradation” can apply to temporary or permanent failure.
3.16
direct current charging artificial network
DC-charging-AN
network inserted in the high voltage DC lead of vehicle in charging mode which provides, in a given frequency
range, a specified load impedance and which can isolate the vehicle from the HV DC charging station in that
frequency range
3.17
dual directional coupler
four-port device consisting of two transmission lines coupled together in such a manner that a single
travelling wave in any one transmission line will induce a single travelling wave in the other, the direction of
propagation of the latter wave being dependent upon that of the former
3.18
electric vehicle supply equipment
EVSE
equipment or a combination of equipment, providing dedicated functions to supply electric energy from a
fixed electrical installation or supply network to an electric vehicle for the purpose of charging
3.19
electromagnetic compatibility
EMC
ability of equipment or system to function satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbance (3.20) to anything in that environment
3.20
electromagnetic disturbance
any electromagnetic phenomenon which can degrade the performance of a device, equipment, or system or
adversely affect living or inert matter
EXAMPLE An electromagnetic disturbance can be an electromagnetic noise, an unwanted signal, or a change in
the propagation medium itself.
3.21
electromagnetic interference
EMI
degradation of the performance of equipment, transmission channel, or system caused by electromagnetic
disturbance (3.20)
Note 1 to entry: The English words “interference” and “disturbance” are often used indiscriminately.
3.22
electromagnetic radiation
phenomenon by which energy in the form of electromagnetic waves emanates from a source into space;
energy transferred through space in the form of electromagnetic waves
Note 1 to entry: By extension, the term “electromagnetic radiation” sometimes also covers induction phenomena.
3.23
forward power
power supplied by the output of an amplifier or generator
3.24
ground reference plane
flat conductive surface whose potential is used as a common reference

3.25
immunity to a disturbance
ability of a device, equipment, or system to perform without degradation in the presence of an electromagnetic
disturbance (3.20)
3.26
lowest usable frequency
LUF
lowest frequency for which the field uniformity requirements are met for the reverberation chamber method
and at least 12 independent stirring configurations can be achieved
3.27
net power
forward power (3.23) minus reflected power (3.32)
3.28
polarization
property of sinusoidal electromagnetic wave or field vector defined at a fixed point in space by the direction
of the electric field strength vector or of any specified field vector, when this direction varies with time
Note 1 to entry: The property can be characterized by the locus described by the extremity of the considered field vector.
3.29
portable transmitter
hand-held radio frequency (RF) communication device
3.30
power mains
general purpose alternating current (a.c.) or direct current (d.c.) electric power supply
3.31
pulse modulation
PM
process by which the amplitude of a carrier wave is varied following a specified law, resulting in a PM signal
3.32
reflected power
reverse power
power reflected by the load due to impedance mismatch between radio frequency (RF)-source and load
3.33
reverberation chamber
high Q shielded room (cavity) whose boundary conditions are changed via one or several rotating tuners
or moving walls (including Vibrating Intrinsic Reverberation Chambers (VIRC) with or without conductive
contact to the floor) or repositioning of the transmitting antenna(s)
Note 1 to entry: This results in a statistically uniform electromagnetic field.
Note 2 to entry: VIRC is defined in ISO 11451-5.
3.34
shielded enclosure
mesh or sheet metallic housing designed expressly for the purpose of separating electromagnetically the
internal and external environment
3.35
susceptibility
inability of a device, equipment or system to perform without degradation in the presence of an
electromagnetic disturbance (3.20)
Note 1 to entry: Susceptibility is the lack of immunity.

3.36
susceptibility threshold
minimum level of a given electromagnetic disturbance (3.20) incident on a particular device, equipment or
system for which it does not operate at a required degree of functional performance
3.37
test generator
generator capable of generating the required test signal
Note 1 to entry: The test generator can, e.g. include a vector signal generator, modulation sources, attenuators,
broadband power amplifiers and filters.
3.38
transmission line system
TLS
field-generating device that works in a similar way to a TEM (transverse electromagnetic) wave generator
EXAMPLE Stripline, TEM cell, parallel plate.
3.39
tubular wave coupler
TWC
device to couple RF power to a harness or a conductor without interrupting the conductor and without
introducing significant impedance into the associated circuits
3.40
voltage standing wave ratio
VSWR
ratio, along a transmission line, of a maximum to an adjacent minimum magnitude of a particular field
component of a standing wave
Note 1 to entry: This ratio is equal to: (1+|Γ|)/(1-|Γ|) where |Γ| is the magnitude of the complex reflection factor Γ.
3.41
white noise
flat random noise
random noise which has a continuous spectrum and a constant power spectral density in the frequency
band considered
4 General aim and practical use
The test methods, procedures, test instrumentation, and levels specified in the ISO 11451 series are intended
to facilitate vehicle specification for electrical disturbances by narrowband radiated electromagnetic
energy. A basis is provided for mutual agreement between vehicle manufacturers and component suppliers
intended to assist rather than restrict.
Certain devices are particularly susceptible to some characteristics of electromagnetic disturbance, such as
frequency, severity level, modulation or type of coupling.
Electronic devices are sometimes more susceptible to modulated, as opposed to unmodulated, RF signals.
The reason is that high-frequency disturbances can be demodulated by semiconductors. In the case of
unmodulated signals, this leads to a continuous shift of, for example, a voltage; in the case of amplitude-
modulated signals, the resulting low-frequency fluctuations can be interpreted as intentional signals (e.g.
speed information) and therefore, disturb the function of the vehicle under test more severely.
A single standard test might not reveal all the needed information about the vehicle under test. It is thus
necessary for users of the ISO 11451 series to anticipate the appropriate test conditions, select applicable
parts of the ISO 11451 series, and define function performance objectives. The main characteristics of each
test method in ISO 11451-2 to ISO 11451-5 are presented in Table 1.

Table 1 — Main characteristics of test methods in the ISO 11451 series
Part of the ISO 11451 Applicable fre- Test severity pa-
Coupling to Provisions
series quency range rameter and unit
ISO 11451-2
Components and
10 kHz to 18 GHz Electric field (V/m) ALSE required
Off-vehicle radiation
wiring harness
sources
ISO 11451-3
Components and
1,8 MHz to 6 GHz Power (W) ALSE recommended
On-board transmitter
wiring harness
simulation
ISO 11451-4
Current (mA) or Shielded enclosure rec-
100 kHz to 3 GHz Wiring harness
Harness excitation meth-
Power (dBm) ommended
ods
ISO 11451-5
10 kHz or LUF to Components and Reverberation chamber
Electric field (V/m)
18 GHz wiring harness required
Reverberation chamber
5 General test conditions
5.1 General
Unless otherwise specified, the following test conditions are common to all parts of the ISO 11451 series:
— test temperature;
— supply voltage;
— modulation;
— dwell time;
— frequency step sizes;
— definition of test severity level;
— test signal quality.
NOTE 1 The use of the same parameters as those used for the vehicle test methods given in the corresponding parts
of the ISO 11452 series will achieve better correlation.
Unless otherwise specified, the variables used shall have the following tolerances:
— ±10 % for durations and distances;
— ±10 % for resistances and impedances;
and the following magnitude accuracy:
— ±1 dB for power meter including power sensor;
— ±3 dB for field probe.
NOTE 2 When estimating the instruments' uncertainty, the calibration results and the uncertainties of the
calibration laboratory can be used.
5.2 Test temperature
Heat is generated in the test facility when the vehicle is operated during the performance of the test.
Sufficient cooling shall be provided to ensure that the engine does not overheat.
The ambient temperature during the test should be (23 ± 5) °C.

5.3 Supply voltage
5.3.1 Vehicle low voltage (LV) power supply
LV is used for DC operating voltages below 60 V (e.g. 12 V, 24 V, 48 V). For tests that require the vehicle
engine to be running, the electrical charging system shall be functional. For tests where the vehicle engine
is not required to be running, unless other values are specified in the test plan, the battery voltage shall be
maintained above 12 V for 12 V systems, above 24 V for 24 V systems and above 48 V for 48 V systems.
5.3.2 Hybrid or electric vehicle not connected to power mains
The supply voltage and tolerances for high voltage electrical systems operating above 60 V d.c. shall be
documented in the test plan.
5.3.3 Hybrid or electric vehicle in charging mode (a.c. or d.c.)
The DC power supply voltage during the test shall be nominal ±10 %.
The AC power supply voltage during the test shall be nominal −15 % to +10 %. The rated value of the
frequency shall be nominal ±1 %.
5.4 Modulation
The characteristics of the vehicle under test determine the type and frequency of modulation to be used.
If no values or specific modulation techniques are agreed between the users of the ISO 11451 series, the
following modulations shall be used:
a) unmodulated sine wave (CW), see Figure 1 a);
b) sine wave amplitude modulated (AM) by 1 kHz sine wave at 80 % (modulation index m = 0,8) [see
Annex C and Figure 1 b)];
c) sine wave pulse modulated type 2 (PM, similar to radar), with t = 3 µs and period = 3 333 µs [see
on
Figure 1 c)];
d) sine wave pulse modulated type 3 (PM, similar to digital mobile services), with t = 500 µs and period =
on
1 000 µs [see Figure 1 d)].
a) CW signal b) AM signal
c) PM type 2 signal d) PM type 3 signal

Key
X time [µs]
Y test signal, expressed as electric field, current or power
f modulation frequency
NOTE 1 Dashed lines denote the test signal envelopes.
NOTE 2 Dash dotted lines denote the peak values of the test signals.
Figure 1 — Modulation
The following modulations should be used for all applicable parts of the ISO 11451 series:
— CW: 10 kHz to 18 GHz;
— AM: 10 kHz to 400 MHz;
— PM type 2: 2,7 GHz to 3,1 GHz;
— PM type 3: 380 MHz to 2,7 GHz and 3,1 GHz to 18 GHz.
Alternative broadband test signal generation (e.g. for digital broadcast and communication systems
frequency bands) which is described in Annex D may be used if intended by a particular standard of the
ISO 11451 series (i.e. as referenced in the published edition of ISO 11451-3:2024).
5.5 Dwell time
At each frequency, the vehicle shall be exposed to the test level for a time equal to the response time of the
vehicle system. If a dwell time is not specified in the test plan, or system response time is not specified, then
the dwell time shall be a minimum of 1 s.
5.6 Frequency step sizes
All tests in the ISO 11451 series shall be conducted with frequency step sizes (logarithmic or linear) not
greater than those specified in Table 2. The step size agreed upon by the users of this document shall be
documented in the test plan and in the test report.
For tests performed with broadband signals, according to Annex D, different step size deviating from Table 2
may be used depending on the bandwidth of the signal.
Table 2 — Maximum frequency step sizes
Frequency band Linear steps Logarithmic steps
10 kHz to 100 kHz 10 kHz 10 %
>100 kHz to 1 MHz 100 kHz 10 %
>1 MHz to 10 MHz 1 MHz 10 %
>10 MHz to 200 MHz 5 MHz 5 %
>200 MHz to 400 MHz 10 MHz 5 %
>400 MHz to 1 GHz 20 MHz 2 %
>1 GHz to 18 GHz 40 MHz 2 %
If it appears that the susceptibility thresholds of the vehicle under test are very near to the chosen test level,
these frequency step sizes should be reduced in the frequency range concerned in order to find the minimum
susceptibility thresholds.
5.7 Definition of test severity levels
The user should specify the test severity level or levels over the frequency range. The concept of FPSC
detailed in Annex A shall be used for specifying the test severity level or levels over the frequency range.
For both the substitution and closed loop levelling methods, and for tests with unmodulated and amplitude-
modulated signals, the test severity levels of the ISO 11451 series (electric field, current or power) are
expressed in terms of the equivalent root-mean-square level value of the unmodulated wave.
Both these methods use a constant peak test level for tests with unmodulated and amplitude-modulated
signals. The relationship between the mean power for the amplitude-modulated signal and the mean power
for the unmodulated signal results from this principle shall be calculated as in Annex C.
5.8 Evaluation of test instrumentation uncertainties
Annex E provides general guidance for estimating test instrumentation uncertainties. Each part of
the ISO 11451 series may provide a detailed influent parameter for instrumentation and a specific
budget associated with each test method.
6 Instrumentation
6.1 DC-charging-AN, AMN, and AAN
The networks (DC-charging-AN, AMN, and AAN) to be used (when required by an individual test method)
for a vehicle in charging mode connected to the power grid are defined in Annex B. Annex B shall therefore
be followed.
6.2 Test signal quality
In the frequency range limited by the bandwidth of both the amplifier and the antenna (transducer) in use,
each amplifier output harmonic shall be limited to −12 dB (up to the fifth harmonic) for frequencies below
or equal to 1 GHz, −6 dB (up to the third harmonic) for frequencies above 1 GHz, relative to the carrier wave,
unless otherwise specified for a particular test method or in the test plan.
This characteristic shall be verified at least for the maximum used test level, wit
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