In defence, controlling the electromagnetic environment is essential to the availability and operational safety of critical systems.
EMC testing applies to equipment and subassemblies as well as to complete materiel and systems: conducted or radiated emissions and susceptibility, transients and severe electromagnetic environments.
Standards such as MIL-STD 461 govern testing of equipment and subsystems in particular, supplemented, depending on the programme, by further requirements applicable to materiel and systems. HEMERA RF supports their normative and operational qualification with EMC, RF, HEMP and transient solutions.
Defence EMC: qualification, availability and control of the electromagnetic environment
EMC testing applies to equipment and subassemblies as well as to complete materiel, platforms and systems: conducted or radiated emissions and susceptibility, electrical transients, high-intensity electromagnetic fields and severe electromagnetic environments.
Applicable requirements depend on the level under consideration (equipment, subsystem or system), but also on the platform, its operational environment and programme-specific specifications.
HEMERA RF supports manufacturers and laboratories in defining and integrating EMC, RF, microwave, HEMP and transient test facilities, from the technical qualification of requirements through to commissioning and metrology follow-up.
MIL-STD-461:
EMC testing of equipment and subsystems
MIL-STD-461 is one of the main standards for controlling electromagnetic interference in military equipment and subsystems.
It defines a range of emission and susceptibility requirements grouped into four main families: CE, RE, CS and RS.
Depending on the tests and applicable requirements, the phenomena considered can range from very low frequencies up to RF and microwave, at levels representative of military electromagnetic environments.
CE: Conducted Emissions
CE tests characterise the conducted emissions generated by the equipment that may propagate through its power supplies, cables and interfaces.
Depending on the tests, measurements can extend from low frequencies up to several tens of MHz.
The aim is to verify that the disturbances produced by a piece of equipment remain compatible with the other equipment integrated within the system.
RE: Radiated Emissions
RE tests measure the electromagnetic emissions radiated by the equipment and its cabling.
Depending on the application, measurements can extend from low frequencies up to potentially several tens of GHz.
Controlling emissions is particularly important when equipment is installed close to sensitive systems: radio receivers, communications, navigation, radar or other electronic equipment.
CS Conducted Susceptibility
CS tests verify a piece of equipment's ability to operate when subjected to conducted disturbances injected onto its cables and interfaces.
They cover very different phenomena: low-frequency disturbances, RF injection and fast electrical transients.
Commonly encountered tests include CS106, CS114, CS115 and CS116.
CS 114
CS114 verifies the immunity of cables and interfaces to conducted RF disturbances.
As an order of magnitude, tests can cover a wide band from the kHz range up to several hundred MHz, with injection levels depending on the application and the environment considered.
They require, in particular, RF generators, amplifiers, injection clamps, current probes, and measurement and control systems.
CS 115 and CS 116
CS115 reproduces fast transient pulses applied to cabling, while CS116 addresses damped sinusoidal transients at various frequencies.
These tests illustrate the need to supplement continuous-wave RF testing with equipment able to generate and measure fast pulsed phenomena.
RS Radiated Susceptibility
RS tests verify how a piece of equipment behaves when subjected to radiated electromagnetic fields.
They are a major concern in defence because of the presence of radars, communication systems, jammers and other high-power RF transmitters.
Depending on the applicable requirements, a test such as RS103 can cover a range from a few tens of MHz up to several tens of GHz.
Field levels can reach several tens, or even several hundred, V/m in certain environments and applications.
Covering such a wide frequency band often requires several amplifiers and several antenna technologies.
MIL-STD-461 thus addresses the four fundamental dimensions of equipment EMC:
CE / RE: what the equipment emits
CS / RS: what the equipment must withstand
MIL-STD-464: from equipment to the complete platform
Defence EMC does not stop at the qualification of individual equipment.
MIL-STD-464 addresses electromagnetic environmental effects (E3) at the level of military systems and platforms.
It therefore complements the MIL-STD-461 approach:
MIL-STD-461 → equipment and subsystems
MIL-STD-464 → systems and platforms
This approach takes into account the real electromagnetic environment in which the materiel must operate: coexistence of multiple transmitters, proximity to radars or high-power communication systems, integration of many electronic devices within a single platform, or exposure to severe electromagnetic environments.
The aim is to ensure that integrating the various pieces of equipment does not compromise the operational performance, availability or operational safety of the complete system.
From low frequencies to microwave
One of the distinctive features of defence applications is the sheer range of electromagnetic phenomena to be reproduced or measured.
For information, tests can span several decades of frequency, from conducted disturbances in the kHz range up to radiated tests reaching several tens of GHz, with fields of up to several hundred V/m depending on the application.
Such broad frequency coverage generally calls for several complementary technologies:
- RF and microwave generators
- amplifiers suited to different bands
- low-frequency, broadband or microwave antennas
- field probes
- power meters and power sensors
- coupling and injection devices
- measurement and control systems.
The values actually applicable are determined by the standard, the platform and the specific requirements of each programme.
CW, modulation and pulse: reproducing different electromagnetic environments
Military environments are not made up solely of continuous RF signals.
Depending on the application, tests may use CW (Continuous Wave), modulated or pulsed signals, in particular to reproduce different environments associated with communication systems, radars or high-power transmitters.
The constraints placed on an RF chain then differ.
A system designed to generate high fields must be sized taking into account:
- the frequency band
- the target field level
- CW or pulsed operation
- modulation characteristics
- average and peak power
- antenna gain and behaviour
- RF chain losses
- test distance and installation geometry.
The ability to cover a very wide frequency band, high levels and different signal types at the same time is therefore a major technical challenge in the design of defence test facilities.
High fields and large equipment under test
Defence tests may involve EUTs (Equipment Under Test) of widely varying sizes, from an electronic unit or a rack up to subsystems, vehicles or complete materiel.
For large EUTs, reaching a high field level at a single point is not enough. The test area or volume, the field distribution, the exposure distance and the various configurations of the materiel must also be taken into account.
The size of the EUT therefore has a direct impact on:
- the dimensions of the chamber or test area
- the distance between the antenna and the EUT
- the required RF power
- the choice and positioning of antennas
- field measurement and control
- cabling and external interfaces
- positioning equipment
- safety devices.
The test facility must therefore be designed as a complete system, not simply as an amplifier paired with an antenna.
Controlling and monitoring the EUT during testing
A susceptibility test is not just about exposing equipment to a field or injecting a disturbance into it. Its functional behaviour must also be checked during the test.
This requirement becomes particularly important for complex materiel and systems, whose operation may depend on numerous devices, interfaces, communications, computers, sensors or actuators.
The test system may therefore need to:
- control the various operating modes of the EUT
- drive the EUT during exposure
- monitor its critical parameters in real time
- monitor communications or functional states
- detect faults or performance degradation
- log events
- synchronise these events with the exposure sequence
- correlate an anomaly with the applied frequency, field level, modulation or pulse.
This is where automation comes into its own. It coordinates the RF chain, the measuring instruments and functional monitoring of the EUT to improve the repeatability, traceability and analysis of tests.
A complete test architecture
Building a high-field defence test facility therefore requires a global approach that goes well beyond simply supplying an amplifier or an antenna.
It must cover a very wide frequency spectrum, generate the required levels in CW, modulated or pulsed mode, control the field over EUTs that are sometimes very large, and monitor their functional behaviour during exposure.
These constraints require the following to be sized together:
generation → amplification → antennas/injection → field and power measurement → test control → EUT monitoring → results acquisition.
HEMERA RF sizes and integrates these functions within a coherent, automated architecture, selecting the technologies and equipment best suited to each frequency band and each type of test.
MIL-STD-188-125 and HEMP
Some defence applications also need to take into account high-altitude electromagnetic pulse – HEMP (High-Altitude Electromagnetic Pulse).
The MIL-STD-188-125 series addresses, in particular, HEMP protection of ground-based facilities and systems performing critical missions.
These environments have very different characteristics from continuous-wave RF testing. They can combine high amplitudes, extremely short rise times and very broad spectral content.
For the fastest components, the phenomena considered can have characteristic times of the order of a few nanoseconds.
HEMP testing and verification may therefore require dedicated equipment to generate high-amplitude pulses, perform cable injection, characterise protection devices or measure extremely fast transient phenomena.
HEMERA RF addresses these challenges with solutions dedicated to HEMP and fast high-voltage transients, complementing conventional EMC and RF test equipment.
GAC: addressing EMC from the design stage
Beyond qualification testing, controlling EMC means taking it into account from the design stage of the materiel or system.
The GAC (Guide d’Aide à la Conception, a design guide) follows this approach, providing recommendations for integrating EMC constraints early in development.
This approach covers, in particular:
- the electrical and electronic architecture
- shielding
- cabling and cable routing
- filtering
- grounding and earthing
- interfaces between equipment
- integration of equipment into the platform
- consideration of the operational electromagnetic environment.
The aim is to treat EMC not merely as a validation step at the end of development, but as a constraint built in from the design stage, reducing the risk of non-compliance and late modifications.
From the standard to the defence test facility
Designing a test facility starts with identifying the standard, the tests to be performed, the levels to be reached, the signal types and the frequency ranges to be covered.
Depending on the project, HEMERA RF can size and integrate RF and microwave generators, high-power amplifiers, antennas, EMI receivers, LISNs, injection clamps, current and field probes, transient generators, HEMP equipment, shielded and anechoic chambers, positioners and safety devices, together with the software needed to control and automate the whole system.
Covering wide frequency bands, high field levels and CW or pulsed modes often requires combining several technologies and several manufacturers.
The HEMERA RF approach to defence projects
HEMERA RF acts as general contractor and multi-brand integrator, designing test facilities tailored to the specific requirements of defence programmes.
Its involvement can cover the entire project: technical qualification of requirements, analysis of target performance, sizing of RF and transient chains, turnkey project management, sourcing of specialist manufacturers and innovative technologies, hardware and software integration, automation, commissioning and metrology follow-up.
This independence from any single manufacturer makes it possible to find the most relevant solution for each function: generation, amplification, antennas, injection, measurement, positioning, shielding, software and EUT monitoring.
It is particularly well suited to defence applications, where wide frequency coverage, high fields, CW or pulsed signals, large EUTs and functional monitoring during testing must all be integrated into a single architecture.
Experience with major defence players
HEMERA RF draws on experience gained through numerous EMC, RF and severe electromagnetic environment projects carried out for major French defence manufacturers, the DGA (French defence procurement agency) and private test laboratories.
These projects cover all types of equipment under test, addressing emissions, susceptibility, high fields, very wide frequency coverage, CW and pulsed signals, transients and HEMP.
This diversity of projects enables HEMERA RF to understand the technical and normative constraints specific to defence applications and to support its customers from requirements analysis through to the delivery of high-performance, automated and scalable turnkey test facilities.
Frequently asked questions
Frequently asked questions
Defence
Which EMC standards apply to aerospace and defence?
In aerospace and defence, the standards include:
• RTCA DO-160 for airborne equipment
• its European counterpart, EUROCAE ED-14
• various MIL-STD standards for military applications
• specific requirements for individual programmes and platforms
The exact requirements must be identified before sizing the test setup.
What is the difference between HEMP and indirect lightning testing?
Indirect lightning:
• transients associated with a lightning event
• particularly relevant in aerospace applications
HEMP:
• a specific pulsed electromagnetic environment
• its own standards, waveforms and levels
Both fields use transient generation and measurement equipment, but they do not represent the same phenomenon.
What are the CS114, CS115 and CS116 tests?
These methods correspond to different types of conducted susceptibility in the military domain.
They differ in particular in:
• the type of signal
• the frequency range
• the coupling mode
• the levels
• the equipment required
How are fast high-voltage transient pulses generated?
The system must reproduce the required characteristics:
• amplitude
• rise time
• duration
• energy
• impedance
• repetition, where applicable
The generator must be combined with suitable coupling devices and measurement equipment.
How is a high-voltage or high-current pulse measured?
You need to select in particular:
• a suitable voltage probe
• a suitable current probe
• attenuation
• cabling
• a high-speed acquisition system
• sufficient bandwidth
Performance must be assessed across the entire measurement chain.
How do you size a HEMP test chain?
You need to start from:
• the standard
• the waveform
• the amplitude
• the rise time
• the duration
• the energy
• the coupling mode
• the equipment under test
These parameters determine the generator, injection devices, protection and instrumentation.
Which generators, couplers and probes should be used for HEMP testing?
The choice depends on:
• amplitude
• rise time
• duration
• energy
• bandwidth
• injection mode
• the applicable standard
As with an EMC laboratory, a multi-brand approach allows the general contractor to select each component on its performance rather than imposing a single supplier.