Table of contents
Preparing an EMC test, sizing a test bench
or choosing equipment?
This FAQ helps you make the right technical decisions. It answers the questions we are most often asked by laboratories, manufacturers and design offices: how to choose an antenna or an amplifier, when to opt for a GTEM cell rather than an anechoic chamber, which coupling device to select, and how to approach transients, HEMP and test automation.
For specific requirements, our engineers will help you choose the right solution.
EMC / RF testing
What is an EMC test?
An EMC (electromagnetic compatibility) test verifies that an electrical or electronic device:
• operates correctly in its electromagnetic environment
• does not generate excessive interference affecting other equipment
• complies with the emission levels set by the applicable standard
• maintains the expected performance when subjected to electromagnetic disturbances
EMC testing mainly covers conducted and radiated emissions, and conducted and radiated immunity.
What is the difference between an EMC emissions test and an immunity test?
• An emissions test measures the electromagnetic interference generated by the equipment.
• It verifies that this interference stays below the limits set by the applicable standard.
• An immunity test, by contrast, subjects the equipment to defined disturbances.
• It verifies that the equipment continues to operate in line with the expected performance criteria.
Emissions and immunity tests are therefore complementary.
What equipment is needed to carry out EMC testing?
Depending on the method and standard, an EMC laboratory may use:
• EMI receivers or spectrum analysers
• RF generators and power amplifiers
• antennas and field probes
• power meters and power sensors
• LISNs, CDNs, BCI clamps and current probes
• ESD, burst, surge or transient generators
• anechoic chambers, reverberation chambers, Faraday cages or GTEM cells
• control and automation software
HEMERA RF covers EMC, RF and microwave equipment over a stated range from DC to 110 GHz.
What are the main EMC test standards?
Standards depend on the sector, the product and its operating environment. They notably include:
• IEC/EN 61000-4-x for many immunity tests;
• CISPR publications for radio disturbances and their measurement methods;
• CISPR 25 for automotive;
• ISO 11451 / ISO 11452, ISO 7637 and ISO 16750 for automotive;
• RTCA DO-160 / EUROCAE ED-14 for civil aviation;
• various MIL-STD standards for military applications.
How do I choose the equipment for an EMC test bench?
The choice should start from the technical requirement:
• standards and methods to be covered
• frequency ranges
• test levels
• characteristics of the equipment under test
• required power and dynamic range
• coupling devices and instrumentation
• test environment
• automation needs
The test bench must be designed as a complete system, not as a simple collection of instruments.
How can an EMC test bench be automated?
Test software can control:
• generators
• amplifiers
• receivers and analysers
• power meters and sensors
• RF switches
• antenna masts and turntables
• other auxiliary equipment
Drivers allow the software to communicate with the various instruments, making it possible to build an automated multi-brand test bench.
How do you set up a turnkey EMC laboratory?
An EMC laboratory project typically includes:
• technical qualification of the requirement
• identification of the standards
• definition of the architecture
• equipment selection
• supply and integration
• automation
• installation and commissioning
• metrology and calibration management
EMC, RF and microwave antennas
How do I choose an antenna for EMC testing?
The factors to consider include:
• frequency range
• type of test: emissions or immunity
• applicable standard
• gain
• antenna factor
• power handling
• radiation pattern
• installation constraints
Depending on the application, loop, biconical, log-periodic, BiLog or horn antennas may be used, as well as antennas designed for microwave and millimetre-wave frequencies.
What is the antenna factor?
The antenna factor:
• relates the voltage measured at the antenna output to the electric field
• varies with frequency
• is usually expressed in dB/m
• is used to convert a voltage measured by a receiver into a field strength
It is therefore an essential characteristic for radiated emissions measurements.
Why does antenna gain matter in EMC?
Gain:
• describes the antenna’s ability to concentrate energy
• affects the field strength achieved for a given power
• plays a direct role in sizing a radiated immunity test chain
It must be considered together with frequency, distance, radiation pattern, VSWR and the required field uniformity.
Does an EMC antenna need to be calibrated?
For quantitative emissions measurements, you need to know in particular:
• its antenna factor as a function of frequency
• the characterisation conditions
• the associated uncertainty
• the corresponding metrological traceability
Whether calibration is needed, and how often, depends on use and on the applicable requirements.
How do I choose an antenna mast or positioner?
The factors to consider are:
• the weight and dimensions of the antenna
• the required height and travel
• polarisation changes
• positioning accuracy
• the level of automation required
• the electromagnetic influence of the structure
RF / power amplifiers
How do I choose an RF amplifier for EMC testing?
The main criteria are:
• frequency band
• power available across the whole band
• gain
• linearity
• compression
• tolerance to mismatch
• protection features
• the power actually required for the test
Rated power alone is therefore not enough to select the right amplifier.
How much amplifier power is needed for a radiated immunity test?
It depends on:
• the required field strength in V/m
• the test distance
• the antenna gain
• the frequency
• cable and accessory losses
• the test environment
• the required margin
Sizing must be carried out across the entire frequency band.
How much RF power is needed to generate a 10 V/m field?
There is no universal power figure.
The power depends on:
• the antenna gain
• the distance
• the frequency
• RF losses
• the electromagnetic environment
• the required field uniformity
A theoretical estimate allows preliminary sizing, but the actual configuration must be validated by calibration.
How do you calculate the RF power needed to reach a given field strength?
The calculation must take into account:
• the required field
• the antenna-to-equipment distance
• the antenna gain
• cable losses
• losses in couplers, switches and connectors
• an operating margin
Calibration is then used to verify the actual performance of the chain.
Why is rated power not enough to size an EMC test chain?
Because the field strength also depends on:
• the antenna gain
• the frequency
• RF losses
• the distance
• VSWR
• the test environment
• amplifier linearity
You therefore need to size the amplifier, RF chain, antenna and test environment as a whole.
How can RF amplifier saturation be avoided?
In particular, you should:
• keep a margin from the compression point
• monitor output power
• monitor reflected power
• take the load VSWR into account
• check linearity across the operating band
How do I correctly match an amplifier with an antenna?
You should check:
• that the frequency bands are compatible
• impedance
• the antenna’s power handling
• the power available from the amplifier
• the antenna gain
• the required field strength
How do I size an amplifier and antenna chain to reach a given level in V/m?
The approach consists of determining:
• the required field
• the distance
• the frequency band
• the antenna gain
• RF losses
• the power required
• the operating margin
The final performance must then be confirmed by calibration.
Which criteria should be compared before buying an RF power amplifier?
Compare in particular:
• frequency band
• output power across the whole band
• gain
• linearity
• compression
• VSWR tolerance
• permissible reflected power
• protection features
The deciding criterion remains its ability to deliver the required performance in the actual test chain.
How is RF power measured during an EMC test?
You can use:
• a power meter
• one or more power sensors
• a directional coupler
• a means of distinguishing forward and reflected power
Anechoic chambers / Faraday cages / GTEM
What is an EMC anechoic chamber?
An anechoic chamber combines:
• a shielded enclosure
• RF absorber materials
• a controlled electromagnetic environment
It is used for a range of radiated emissions and immunity tests.
What is a semi-anechoic chamber?
It typically has:
• absorber-lined walls
• an absorber-lined ceiling
• a conductive, reflective floor
This configuration reproduces certain conditions specified by standardised methods.
What is the difference between an anechoic chamber and a reverberation chamber?
Anechoic chamber:
• aims to reduce reflections
• uses RF absorbers
Reverberation chamber:
• on the contrary, exploits reflections
• uses a conductive enclosure
• uses stirrers to vary the field distribution
What is a GTEM cell?
A GTEM cell:
• is a shielded electromagnetic structure
• generates a controlled field
• can be used for certain immunity tests
• can also be used for certain emissions characterisations
What is the difference between a TEM cell and a GTEM cell?
Both generate a transverse electromagnetic mode.
The GTEM cell notably features:
• a tapered geometry
• a matched termination
• a design that extends the usable range compared with a conventional TEM cell
GTEM cell or anechoic chamber: which should I choose?
The choice depends on:
• the size of the equipment
• the frequencies
• the test levels
• the standards to be covered
• the available space
• the configurations required
A GTEM cell is a compact solution, whereas a chamber generally offers more configuration options.
Can immunity tests be carried out in a GTEM cell?
Yes, for certain methods, provided you check:
• the available power
• the usable test volume
• field uniformity
• the frequency
• the required level
• compatibility with the applicable standard
Can emissions tests be carried out in a GTEM cell?
Yes, for certain characterisations.
For a compliance measurement, however, you must check that the GTEM method is compatible with the standard and with the purpose of the test.
How do you size an EMC anechoic chamber?
The specifications must define in particular:
• standards and methods
• frequency ranges
• measurement distances
• equipment dimensions
• field strengths
• shielding performance
• absorber performance
• access, ventilation and filtered power supplies
• antenna masts, turntables and automation
How do I choose RF absorbers for an anechoic chamber?
The choice depends on:
• the lowest frequency
• the highest frequency
• the required reflectivity performance
• the chamber geometry
• the available space
Ferrite tiles, pyramidal absorbers or hybrid solutions can be combined.
What are Faraday cage filters used for?
They make it possible to:
• bring certain power supplies or signal lines into the enclosure
• limit the propagation of interference along cables
• preserve shielding performance
How do I choose an RF shielded enclosure?
The factors to consider are:
• frequency range
• required shielding effectiveness
• dimensions
• doors
• feedthroughs
• connectors
• filters
• ventilation
ARACION shielded enclosures and racks
What is an RF shielded enclosure?
An RF shielded enclosure (box or rack) is a screened housing that protects electronic equipment from external electromagnetic interference. It enables reliable, repeatable radio-frequency testing in a controlled electromagnetic environment.
What shielding performance do ARACION enclosures offer?
ARACION shielded enclosures offer shielding effectiveness of up to 120 dB.
Which applications require an RF shielded enclosure?
RF shielded enclosures are used for 5G, Wi-Fi, Bluetooth, IoT and EMC testing, as well as for antenna characterisation, radio module validation and quality control of telecommunications equipment. They integrate into R&D laboratories and automated test benches.
Can ARACION shielded enclosures and cabinets be customised?
Yes. ARACION shielded enclosures can be customised in size, connectivity and equipment. They can integrate RF connectors (SMA, N, BNC), filtered USB, Ethernet or HDMI interfaces, filtered AC/DC power supplies, shielded ventilation and RF absorbers.
What is the difference between an RF shielded enclosure and an anechoic chamber?
Anechoic chambers are mainly used for EMC testing and antenna measurements, particularly on large equipment. More compact, shielded enclosures are particularly well suited to testing wireless communication equipment (5G, Wi-Fi, Bluetooth, IoT), in R&D laboratories or on production test benches.
Injection clamps / current probes / LISNs
What is a BCI current injection clamp?
A BCI (Bulk Current Injection) clamp:
• is placed around the cable or harness
• injects an RF disturbance without direct connection to the conductors
• works on the principle of transformer coupling
• is used for certain conducted immunity tests
What is a BCI test used for?
It is used to:
• inject a controlled RF current into a harness
• assess the immunity of the equipment
• reproduce certain electromagnetic coupling effects on the wiring
This method is widely used in the automotive industry.
What is the difference between an injection clamp and a current probe?
• The injection clamp applies the RF disturbance.
• The current probe measures the RF current flowing in the harness.
They can therefore be used together in the same test chain.
How is a BCI injection clamp calibrated?
Characterisation establishes in particular:
• the relationship between RF power and injected current
• performance as a function of frequency
• the clamp’s characteristics in the configuration defined by the method
The exact procedure depends on the standard used.
What is a LISN?
A LISN (line impedance stabilisation network, “RSIL” in French) is a network that:
• is inserted between the power supply and the equipment
• presents a defined RF impedance
• is used to pick off conducted emissions
• contributes to measurement reproducibility
What is a LISN used for in a conducted emissions test?
It is used in particular to:
• present a controlled impedance to the equipment
• provide RF isolation from the power supply
• route the interference to the EMI receiver
• achieve reproducible measurement conditions
How do I choose a LISN?
The factors to consider are:
• the standard
• the type of power supply
• the number of lines
• voltage
• current
• the required impedance
• frequency range
In the automotive sector, the network must in particular meet the requirements of standards such as CISPR 25.
What is a coupling/decoupling network (CDN)?
A CDN is used to:
• apply a controlled RF disturbance
• couple it onto the cable under test
• limit its propagation towards auxiliary equipment
• achieve reproducible conditions
What is the difference between a LISN and a CDN?
LISN:
• mainly associated with conducted emissions measurement
• provides a defined impedance
CDN:
• mainly used to inject an RF disturbance
• provides both coupling and decoupling
How do I choose a CDN for IEC 61000-4-6 testing?
The factors to consider are:
• cable type
• number of conductors
• currents and voltages present
• frequency
• the characteristics required by IEC/EN 61000-4-6
What equipment is needed for a conducted immunity test?
A test chain may include:
• RF generator
• amplifier
• power meter and power sensors
• CDN or injection clamp
• couplers
• attenuators
• loads
• cables and adapters
• control software
How do I choose the accessories for a conducted test chain?
Check:
• frequency band
• impedance
• power handling
• insertion loss
• matching
• compatibility with the method
ESD / Burst / Surge / transients
What is the difference between ESD, burst and surge tests?
• ESD: electrostatic discharge.
• EFT/burst: bursts of electrical fast transients.
• Surge: higher-energy transient overvoltages.
Waveforms, levels, energies and coupling modes are therefore different.
What is an ESD generator?
It is used to:
• produce standardised electrostatic discharges
• apply contact or air discharges
• assess the immunity of the equipment
IEC/EN 61000-4-2 is a key standard.
How is an ESD test carried out to IEC 61000-4-2?
The following must be defined in particular:
• voltage levels
• polarity
• points of application
• contact or air discharge
• number of discharges
• performance criteria for the equipment
What is the difference between contact and air ESD discharges?
• Contact: the tip is placed on the equipment before the discharge is triggered.
• Air: the charged tip is moved towards the equipment until a spark occurs.
• The contact method generally offers better repeatability.
What is an EFT/burst test?
It reproduces:
• electrical fast transients
• grouped into bursts of pulses
• which typically occur during switching events
The method is defined in IEC/EN 61000-4-4.
What is a surge test?
It reproduces:
• transient overvoltages
• with higher energy than a burst
• applied using defined coupling configurations
IEC/EN 61000-4-5 is a key standard.
Which generator should I choose for IEC 61000-4 testing?
You need to determine which phenomena must be covered:
• ESD
• burst
• surge
• voltage dips and interruptions
• magnetic fields
• other tests in the IEC/EN 61000-4 series
What equipment is needed to carry out ISO 7637-2 testing?
Depending on the test:
• transient generator
• power supply
• networks and loads
• coupling devices
• oscilloscope and probes
• accessories specified by the method
What is the difference between ISO 7637-2 and ISO 11452?
• ISO 7637-2: conducted electrical transients in the automotive environment.
• ISO 11452: immunity of automotive components to electromagnetic disturbances, using various methods.
Can a single generator cover several IEC 61000-4 standards?
Yes, some multifunction systems can cover several phenomena.
However, you should check:
• which functions are actually built in
• the coupling networks required
• the available levels
• the compliance of each function with the relevant method
What is an RF power sensor?
A power sensor is characterised in particular by:
• its frequency band
• its dynamic range
• its maximum power
• its accuracy
• its linearity
• the types of signal it can measure
What is the difference between CW and pulse measurement?
• CW: measurement of a continuous or quasi-continuous signal.
• Pulse: measurement of a pulsed signal.
For pulsed signals, you may need to characterise:
• peak power
• pulse width
• duty cycle
• time-domain behaviour
Why is the linearity of an RF power sensor important?
Good linearity makes it possible to:
• maintain reliable measurements as the power level varies
• reduce errors across the dynamic range used
• better control the power actually applied
What is an isotropic E-field probe?
An isotropic probe:
• measures the electric field along several axes
• gives a reading that is largely independent of its orientation
• can be used for field calibration
• is used in particular in radiated immunity testing
What is the difference between RF power measurement and field measurement?
• RF power describes the energy flowing in a transmission line.
• The electric field describes the electromagnetic environment in space and can be expressed in V/m.
The two measurements are complementary.
Why use several sensors in a test chain?
Because a single sensor may not cover:
• the whole frequency band
• the whole dynamic range
• all power levels
• all signal types
How often should a field probe be calibrated?
The calibration interval depends on:
• use
• the manufacturer’s recommendations
• the stresses the probe is subjected to
• the quality system
• its stability history
How often should an RF power meter be calibrated?
The following should also be considered:
• frequency of use
• criticality of the measurements
• environmental conditions
• recommendations
• metrological history
HEMP (High-altitude Electromagnetic Pulse)
What is a HEMP test?
A HEMP test assesses how an item of equipment or a system behaves when exposed to:
• pulsed electromagnetic disturbances
• fast rise times
• high levels
• phenomena corresponding to the HEMP environment under consideration
The methods and levels depend on the applicable standard.
What is a high-altitude electromagnetic pulse?
A HEMP (high-altitude electromagnetic pulse):
• is associated with a nuclear event at high altitude
• can produce an electromagnetic disturbance over a very wide area
• can couple onto structures and cables
• can disrupt electrical and electronic systems
What equipment is needed to carry out HEMP testing?
Depending on the method:
• pulse generators
• high-voltage or high-current generators
• coupling devices
• injection networks
• high-voltage probes
• current probes
• high-speed acquisition systems
• suitable accessories and protection
Which standards govern HEMP testing?
The applicable standard depends on the programme.
• MIL-STD-188
• MIL-STD-464
• MIL-STD-461
• CS106
• CS114
• CS115
• CS116
EMC / RF / radio software and automation
What is EMC test software used for?
It is used to:
• control the instruments;
• run the test sequences;
• acquire the measurements;
• record the results;
• coordinate the various equipment in the bench;
• improve traceability.
Drivers make it possible to integrate equipment from different manufacturers.
Why automate EMC testing?
Automation makes it possible to:
• improve repeatability
• increase productivity
• reduce manual operations
• control test sequences
• ensure traceability
• record results automatically
Can a radiated immunity test be automated?
Yes. The software can coordinate:
• generator
• amplifier
• power meter
• field probe
• switches
• positioners
• monitoring of the equipment under test
Can a conducted immunity test be automated?
Yes. It can automate in particular:
• RF generation
• frequency changes
• modulation
• applied level
• power acquisition
• use of calibration data
• monitoring of the equipment under test
How can a radiated emissions measurement be automated?
The software can coordinate:
• EMI receiver or analyser
• antenna mast
• polarisation
• turntable
• frequency sweeps
• search for critical frequencies
• final measurements
Which instruments can EMC software control?
Depending on the drivers available:
• generators
• amplifiers
• EMI receivers
• analysers
• power meters
• sensors and probes
• oscilloscopes
• power supplies
• switches
• antenna masts
• turntables
Can equipment from different brands be controlled by the same software?
Yes, and this is a key point when designing a high-performance, scalable EMC laboratory.
• A laboratory should not be designed around an obligation to use a single brand.
• Each function must be analysed independently.
• The general contractor or integrator selects the most suitable equipment, regardless of brand.
• The choice depends on performance, standards, compatibility and budget.
• Drivers allow the software to communicate with these different instruments.
• This architecture reduces dependence on a single manufacturer and makes it easier to upgrade the laboratory.
Can software automate both EMC and radio tests?
Depending on its functions and drivers, it can automate:
• EMC tests
• RF measurements
• certain radio measurements
• instrument control
• frequency sequences
• acquisition and processing of results
What are the benefits of an automated EMC test system?
They include:
• repeatability
• productivity
• traceability
• fewer manual interventions
• automation of complex sequences
• multi-brand integration
• easier upgrading of the test bench