CISPR 25

Latest version of CISPR 25, Edition 5.0 requires emissions tests from 150 kHz to 5925 MHz. This is an EMC standard that defines RF emissions requirements. Conducted Emissions and Radiated Emissions are the two main test type.

Conducted Emissions tests are performed to ensure the RF emissions on EUT’s ports/cables are under the limits. LISNs and measuring receiver are the two main test setup requirements for this test. Radiated Emissions tests are performed to ensure the RF emissions from EUT’s enclosure are under the limits. Antennas and measuring receiver are the main test setup requirements for this test.

About CISPR 25

Current version of CISPR 25 is 5.0 and this new edition is recently published by IEC. What are the differences when compared to previous version (4.0)? Main change is the frequency range is extended. CISPR 25:2021 requires conducted and radiated emissions testing in this frequency range: 150 kHz to 5,925 MHz. Another change is inclusion of measurement uncertainty annexes to new version. Since Edition 4.0 has been expired, Edition 5.0 can be used. Some regulatory bodies, countries and test laboratories are adapting to this new version due to its fundamental changes affecting testing and reporting. 

CISPR 25 includes both conducted emissions and radiated emissions tests. For magnetic field emissions testing CISPR 36 is used. For immunity tests, ISO 11452 standard series are used. 

Which products are under the scope of CISPR 25? 

Comparison between CISPR 25:2016 and CISPR 25:2021

The most essential difference between the previous version and recent version is upper frequency. With CISPR 25:2021 (Edition 5.0), upper frequency goes up to 5,925  MHz instead of 2,500 MHz. 

CISPR 25: 2021 (Edition 5.0)

Let us review CISPR 25:2021

Title

Vehicles, boats and internal combustion engines – Radio disturbance characteristics – Limits and methods of measurement for the protection of on-board receivers

Languages

English and French. Most of IEC publications are multilingual and the languages are English and French. 

How to preview the free version? 

IEC publishes preview versions of the standards free of charge. Click here to reach preview version of CISPR 25:2021

How to purchase and download the full version? 

IEC sells the full version of their standards via their online store. You need to create a user profile on the online store. You can either purchase a single-user or multi-user copy. Click here to reach online online store page of CISPR 25:2021. You can purchase full version of CISPR 25 via other parties like national standards institutes, regional standard committees who are collaborating with IEC. 

Scope of CISPR 25:2021 (Edition 5.0)

The standard contains limits and procedures for the measurement of radio disturbances in the frequency range of 150 kHz to 5 925 MHz. It applies to 

vehicles, boats, internal combustion engines, trailers, devices and any electronic/electrical component intended for use in vehicles, boats, trailers and devices. 

The limits are intended to provide protection for on-board receivers installed in a vehicle from disturbances produced by components/modules in the same vehicle. The receiver types to be protected are, for example, broadcast receivers, land mobile radio, radio telephone, amateur, citizens’ radio, Satellite Navigation, WiFi, V2X, and Bluetooth. 

The standard does not include protection of electronic control systems from radio frequency (RF) emissions or from transient or pulse-type voltage fluctuations. These subjects are included in ISO publications. 

The limits in CISPR 25:2021 are recommended and subject to modification as agreed between the customer (e.g. vehicle manufacturer) and the supplier (e.g. component manufacturer). The standard is also intended to be applied by vehicle manufacturers and suppliers which are to be added and connected to the vehicle harness or to an on-board power connector after delivery of the vehicle. 

CISPR 25:2021 defines test methods for use by vehicle manufacturers and suppliers, to assist in the design of vehicles and components and ensure controlled levels of on-board radio frequency emissions. The emission requirements are not intended to be applicable to the intentional transmissions from a radio transmitter as defined by the ITU including their spurious emissions. However, this exclusion is limited to those intended transmitter emissions, which leave the EUT as radiated emissions and are coupled onto the wire line in the measurement setup. For conducted transmissions on frequencies intentionally produced by the radio part of an EUT, this exclusion does not apply. It is usual for customers and suppliers to use radio regulation standards to manage the effect of spurious emissions from a radio transmitter unless limits of spurious emission are agreed in the test plan.

Definitions

The standard list the definitions of essential terms.

Absorber Lined Shielded Enclosure (ALSE): shielded enclosure/screened room with radio frequency-absorbing material on Its internal ceiling and walls

Antenna Factor: factor which is applied to the voltage measured at the input connector of the measuring instrument to give the field strength at the antenna

Antenna Matching Unit: unit for matching the impedance of an antenna to that of the 50 R measuring instrument over the antenna measuring frequency range

Artificial Mains Network (AMN): network that provides a detailed impedance to the EUT at radio frequencies, couples the disturbance voltage to the measuring receiver and decouples the test circuit from the supply mains

Note 1: 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 interchangeably

Note 2: Network inserted in the power mains of the vehicle in charging mode or of a component (e.g. charger) which provides, in a given frequency range, a specified load impedance and which isolates the vehicle component from the power mains in that frequency range..

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 or disturbance voltages and which can isolate the apparatus from the supply or signal sources/loads in that frequency range

Note 1: Network Inserted in the DC power lines of the vehicle in charging mode which provides, in a given frequency range, a specified load impedance and which isolates the venice from the DC power supply in that frequency range.

 

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: This network is inserted in the communication/signal lines of the vehicle in charging mode or of a component (e.g charger) to provide a specific load impedance and/or a decoupling (e.g. communication/signal lines and power mains). The AAN is also used in CISPR 25:2021 for symmetric lines.

 

Bandwidth <equipment> : width of a frequency band over which a given characteristic of an equipment or transmission channel does not differ from its reference value by more than a specified amount or ratio

Note 1: The given characteristic may be, for example, the amplitude/frequency characteristic, the phase/frequency characteristic or the delay/frequency characteristic.

Bandwidth <emission or signal> : the width of the frequency band outside which the level of any spectral component does not exceed a specified percentage of a reference level

 

Boat: vessel intended to be used on the surface of water, its length being no greater than 15 m intended to carry persons or goods and equipped with either an inboard or outboard engine

 

Bonded ‹ground connection and DC resistance>: grounding connection with a DC resistance not exceeding 2.5 mohm and that provides the lowest possible impedance (resistance and inductance) connection between two metallic parts (see 5.3 of CISPR 16-2-1:2014/AMD1:2017)

Note 1: A low current (<100 mA) 4-wire milliohm meter is recommended for this measurement

Broadband Emission: emission which has a bandwidth greater than that of a particular measuring apparatus or receiver

Note 1: An emission which has a pulse repetition rate (in Hz) less than the bandwidth or a particular measuring instrument can also be considered as a broadband emission.

 

Charging Mode: mode that is intended to charge the traction battery with one of the following four categories: described from 3.11.1 to 3.11.4

Charging Mode 1: charging mode as defined in IEC 61851-1:2017, 6.2.1

Note 1: In some countries, mode 1 charging is prohibited or requires special precautions.

Charging Mode 2: charging mode as defined in IEC 61851-1:2017, 6.2.2 where the vehicle is connected to AC mains using a charging cable including an Electric Vehicle Supply Equipment (EVSE) box providing control pilot signaling between the vehicle and the EVSE box and personal protection against electric shock

Note 1: In some countries, special restrictions are applied for mode 2 charging

Note 2: : There is no communication between the venice and the AC supply network (mains)

Charging Mode 3: charging mode as defined in IEC 61851-1:2017, 6.2.3 where the vehicle is connected to ar EVSE (e.g charging station, wall box) providing AC power to the vehicle with communication between the vehicle and the charging station (through signal/control lines and/or through wired network lines)

Charging Mode 4: charging mode as defined in IEC 61851-1:2017, 6.2.4 where the vehicle is connected to an EVSE providing DC power to the vehicle (with an off-board charger) with communication between the vehicle and the charging station (through signal/control lines and/or through wired network lines)

Class: performance level agreed upon by the customer and the supplier and documented in the test plan

Compression Point: input signal level at which the gain of the measuring system becomes non-linear such that the indicated output deviates from an ideal linear receiving system’s output by the specifier increment in dB

Controller Area Network (CAN): network documented in ISO 11898-1 that connects devices, sensors and actuators in systems.

Device: machine driven by an internal combustion engine which is not primarily intended to carry persons or goods

Note 1: Devices include, but are not limited to, chainsaws, irrigation pumps, snow blowers, air compressors, and landscaping equipment.

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

Disturbance Voltage: interference voltage (deprecated in this sense) voltage produced between two points on two separate conductors by an electromagnetic disturbance. measured under specified conditions

Electric Vehicle: vehicle propelled exclusively by electric motor(s) powered by on-board traction battery or oateres

Equipment Under Test (EUT): vehicle, boat, device, component, module or internal combustion engine within CISPR 25:2021 (Edition 5.0)

Hybrid Electric Vehicle: vehicle propelled by electric motor(s) and internal combustion engine

Note 1: The two propulsion systems can operate individually or in a combined mode depending on the hybrid system

Note 2: Vehicle where the electric motor is used to start the internal combustion engine are not considered as a hybrid vehicle

High Voltage (HV):  operating DC voltage between 60 V to 1 000 V

Note 1: The term high voltage can be defined with a different voltage range in other standards.

High Voltage Artificial Network (HV-AN): network inserted in the high voltage DC 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 in that frequency range

Low Voltage (LV): operating DC voltage below 60 V, e.g. nominal voltages of 12 V, 24 V or 48 V

Note 1: he term low voltage can be defined with a difterent voltage range in other standards

Measurement Time: effective, coherent time for a measurement result at a single frequency

• for the peak detector, the effective time to detect the maximum of the signal envelope,
• for the quasi-peak detector, the effective time to measure the maximum of the weighted

envelope

• for the average detector, the effective time to average the signal envelope

Narrowband Emission: emission which has a bandwidth less than that of a particular measuring apparatus or receiver

Note 1: An emission which has a pulse repetition rate (in Hz) greater than the bandwidth of a particular measuring instrument can also be considered as a narrowband emIssion

Open Area Test Site (OATS):  facility used for measurements of electromagnetic fields the intention for which is to simulate a semi-free-space environment over a specified frequency range that is used for radiated emission testing of products

Note 1: An OATS typically is located outdoors in an open area and has an electrically-conducting ground plane. This is defined in CISPR 16-2-3.

Powerline Communications (PLC): communication technique based on error tolerant modulation schemes which transmits information superimposed to electrical power over lines or cables

Reference Ground Plane: flat conductive surface whose potential is used as a common reference

Note 1: For the purpose of CISPR 25:2021, the reference ground plane is defined as the top metallic surface of the test bench/table

RF boundary: element of an EMC test setup that determines what part of the harness and/or peripherals are included in the F environment and what is excluded

Note: A RF boundary can consist of, for example, ANs, filter feed-through pins, RF absorber coated wire, and/or RF shielding.

Shielded Enclosure: mesh or sheet metallic housing designed expressly for the purpose of electromagnetically separating the internal and the external environment

Signal/Control Port: port intended for the interconnection of components of an EUT, or between an EUT and local auxiliary equipment (AE) and used in accordance with relevant functional specifications (for example for the maximum length of cable connected to it)

Note 1: Examples include RS-232. Universal Serial Bus (USB). High-Definition Multimedia Interface (HDMI), IEEE Std 1394 (‘’FireWire”)

Note 2: For vehicles in charging mode, this includes Control Pilot signal, PLC technology used on Control Pilot signal line and CAN.

Traction Battery: high voltage (HV) battery used for the propulsion of electric or hybrid electric vehicle

Validation Reference Ground Plane: elevated reference ground plane with the dimensions of 2,5 m × 1 m which is used as the standard for modelling in Annex I

Note 1: The validation reference ground plane size and grounding used during the modeling can be different from what a laboratory would use durina tul measurements

Wired Network Port: port for the connection of voice, data and signaling transfers intended to interconnect widely dispersed systems by direct connection to a single-user or multI-user communication network

Note 1: Examples of these include CATV, PSTN, ISDN, xDSL, LAN and similar networks.

Note 2: Wired network ports can support screened or unscreened cables and can also carry AC or DC power where this Is an integral part of the telecommunication specification

Vehicle: machine operating on land which is intended to carry persons or goods or that is operated by a person

Note 1: Vehicles include, but are not limited to cars, trucks, buses, mopeds, agricultural machinery, earth-moving machinery, trailers, material-handling equipment, mining equipment, floor treatment machines, walk-behind floor treatment machines and snowmobiles

Vehicle Inlet / Electric Vehicle Inlet: part of a vehicle coupler incorporated in, or fixed to, the electric vehicle or hybrid vehicle (if equipped)

Requirements common to vehicle and component/module emissions measurement

These requirements are given in the 4th article of the standard. It consists of General Test Requirements, Shielded Enclosure, Absorber Lined Shielded Enclosure (ALSE), Measuring Instrument, Power Supply. Let us review all of these requirements:

1) General Test Requirements

Categories of disturbance sources (as defined in the test plan): narrowband sources and broadband sources. Categorization of the disturbance type is used only in simplifying the testing demands by potentially reducing the number of detectors that shall be used. Type of disturbance does not affect the applicability of limits. 

Test Plan: It shall specify frequency range to be tested, the emissions limits, antenna types and locations, test report requirements, supply voltage and other relevant parameters, including EUT operating conditions. The test plan shall define for each frequency band whether the conformance can be obtained with Average & Peak limits or Average & Quasi-Peak limits. 

Determination of Conformance of Equipment Under Test (EUT) with limits: In all cases the EUT shall conform to the Average limit. The EUT shall also conform to either Peak or Quasi-Peak limits.

The EUT shall also conform to either peak or quasi-peaks limits as follows.

• for frequencies where both peak and quasi-peak limits are defined, the EUT shall conform to either the peak or the quasi-peak limits (as defined in the test plan);
• for frequencies where only peak limits are defined, the EUT shall conform to the peak limit.

The general procedure applicable for all frequency bands is described in Figure 1 of the standard as shown below: 

Operating Conditions: When performing component/module tests, the EUT shall be made to operate under typical loading and other conditions as in the vehicle such that the maximum emission state occurs. To ensure correct operation of components/modules during test, a peripheral interface unit shall be used which simulates the vehicle installation.

Test Report: The report shall contain the information agreed upon by the customer and the supplier, e.g sample identification, date and time of test, bandwidth, step size, required test limit, ambient data and test data.

2) Shielded Enclosure Requirements

The ambient electromagnetic noise levels shall be at least 6 dB below the limits specified in the test plan for each test. The shielding effectiveness of the shielded enclosure shall be sufficient to assure that the ‘6 dB below’ requirement is met. Shielded enclosure, without any absorber, is recommended only for conducted emissions measurements. For simplicity, the standard allows any suitably grounded bench-top screened cages to be used as shielded enclosure. 

Shielded Enclosure (in French version of CISPR 25 it is ‘Cage de Faraday’) is mostly constructed with metallic panels to provide a reasonable shielding effectiveness between inside and outside the enclosure. The most essentail parameter of a shielded enclosure its shielding effectiveness parameters for a frequency range. Shielding Effectiveness measurements of a shielded enclosure are done according to IEEE 299, EN 50147-1 or any other standard (IEEE 299, ASTM F3057-14, ASTM D4935-18, ASTM D4935-99, NSA 94-106, NSA 65-6, IEC 61000-5-7, IEC 61587-3, ANSI/SCTE 48-3, IEC 60512-23-3)

One of the antenna manufacturers in the market, A.H. Systems, on its Shielding Effectiveness Test Guide, mentions the importance of periodic testing of shielded enclosures as follows: ‘Even without changes in compliance standards, they do require periodic testing of enclosures — typically every year or two, depending on the standard — to demonstrate they provide the necessary degree of shielding effectiveness. Ideally that is enough to produce 100 dB of attenuation across an enclosure wall. Between 60 dB and 80 dB might be acceptable for some manufacturers, industries, or applications.’

3) Absorber-Lined Shielded Enclosure (ALSE) Requirements

Radiated emission measurements requires RF absorber material on the walls and ceiling of the shielded enclosure. RF absober material is required to eliminiate or minimize the reflected energy from the walls and ceiling and avoid measurement errors due these reflections. 

Size: Sufficient size to ensure that neither vehicle/EUT nor the test antenna (except the rear part of the horn antenna) shall be closer than 1 meter from the walls or ceiling, or to the nearest surface of the absorber material used thereon. CISPR 25 does not mention exact or minimum dimensions of the ALSE since it depends on the vehicle/EUT sizes. 

Objects in ALSE: In order to reduce any effect, the ALSE shall be cleared of all items. Unnecessary equipment, cable racks, storage cabinets, desks, chair, etc. and the personnel not actively involved in the test shall be excluded from the ALSE. 

ALSE Performance Validation: The standard differentiates the validation into two: Vehicle ALSE and Component ALSE.

For Vehicle ALSE, the the performance of the absorption material shall be greater than or equal to 6 dB, between 70 MHz and 5925 MHz. No absober shall be placed on the floor for vehicle tests. For evaluation of absorber material standard refers to IEEE STD 1128-1998

For Component ALSE, the the performance of the absorption material shall be greater than or equal to 6 dB, between 70 MHz and 5925 MHz. No absober shall be placed on the floor for component tests, however flat ferrite tiles with a maximum thickness of 25 mm can be utilised on the floor for component level testing if the chamber performance in this configuration meets Annex I requirements. For evaluation of absorber material standard refers to IEEE STD 1128-1998

The ALSE performance validation procedure given in Annex I shall be used to evaluate the performance of the ALSE as configured for component radiated emissions testing. This procedure is for evaluating the influences of the chamber, absorber, reference ground plane, reference ground plane grounding, and any other possible cause for measurement variation..

4) Measuring Instrument Requirements

The measuring instrument shall comply with CISPR 16-1-1. The appropriate average detector is the linear detector with meter time constants defined in CISPR 16-1-1. Peak, Quasi-Peak, Average detector, bandwidth requirements, spectrum analyser parameters and scanning receiver parameters are given in the CISPR 25:2021. If needed, in addition to measuring instrument, a preamplifier can be used between the antenna and measurement instrument in order to achieve the 6 dB ambient noise requirement. 

Conducted Emissions Test System: Measuring Receiver (EMI Receiver or Spectrum Analyzer with EMC capability), RF cable and CISPR 25 compliant LISNs/AMNs are the three main components for conducted emissions measurements. Transient limiter, attenuator, reference source and test software are optional items which may be added to the test setup. LISNs/AMNs’ current limit shall fulfill the highest current of the equipment under test or vehicle under test. Conducted Emissions shall be measured in ALSE or shielded enclosure. 

Radiated Emissions Test System: Measuring Receiver (EMI Receiver or Spectrum Analyzer with EMC capability), RF cable, antennas and CISPR 25 compliant test table are the four main components for radiated emissions measurements.  Attenuator, Preamplifier, reference source and test software are optional items which may be added to the test setup. Radiated Emissions shall be performed in ALSE or OATS. 

5) Power Supply Requirements

Supply voltage ranges by referencing the nominal supply voltages, are defined. The power supply requirements are given for five different cases:

* Internal combustion engine vehicle – ignition on, engine off (for systems with 12V, 24V, 48V nominal supply voltage) 

* Internal combustion engine vehicle – engine running (for systems with 12V, 24V, 48V nominal supply voltage) 

* Plug-in hybrid electric or electric vehicle in charging mode (for systems with 12V, 24V nominal supply voltage) 

* Hybrid electric or electric vehicle in running mode (for systems with 12V, 24V nominal supply voltage) 

* Component/module tests (for systems with 12V, 24V, 48V nominal supply voltage) 

For component/module tests, the DC power supply voltage during the test shall be nominal +/-10%. The AC power supply voltage during the test shall be nominal -15% / +10%. The rated value of the frequency shall be nominal -/+1%.

Sample ALSE for testing Electronic Components

This DMC CISPR 25 Anechoic Chamber is used for testing electronic components. The features of this ALSE is given below:
External dimension 5.5m x 5.5m x 3.5m (LxWxH)
Load capacity: 1500 kg (Minimum)
Frequency range: 30 MHz to 40 GHz

As seen below, special grounding is also done to fulfil the CISPR 25 requirement. The requirement says the test table shall be grounded with a conductive as short as possible to the chamber’s ground (metallic enclosure). Thus that copper plates are used for grounding. 

Prepare for CISPR 25 EMC tests

If you are in automotive electronics, you should be increase your CISPR 25 knowledge. Choose one of the recommendations depending on your current status:

1) If you are new to CISPR 25, purchase it and read carefully. GET STANDARD

2) If you would like to add more CISPR 25 knowledge, have some training service from an Automotive EMC consultant, expert or engineer. HAVE TRAINING

3) If you have a newly designed product to be tested according to CISPR 25 and looking for a pre-compliance testing service find a pre-compliance test laboratory whose pricing is affordable. HAVE PRE-COMPLIANCE EMC TESTING SERVICE

4) If you have a product to be tested according to CISPR 25 and start in house testing, build a pre-compliance test laboratory by contacting EMC test equipment suppliers. BUILD PRE-COMPLIANCE EMC LABORATORY

5) If you have a product which is ready to launch, have a fully compliance or accredited  CISPR 25 testing service from an independent test laboratory and certify your product. HAVE FULLY-COMPLIANCE EMC TESTING SERVICE

6) If you have various products to be tested according to CISPR 25 and start in house testing, build a fully-compliance test laboratory by contacting EMC test equipment and anechoic chamber suppliers. BUILD FULLY-COMPLIANCE EMC LABORATORY

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