Principal EMC Consultant at standards testing organisation TÜV SÜD, Pete Dorey examines the latest standards affecting the UK defence industry.
In the military domain, EMC compliance is critical since electromagnetic interference may severely impair radio-communications and the functioning of other devices.
Ministry of Defence (MoD), Def Stan 59-411 Issue 3 was issued on 14 June 2019 and provides the foundation for ensuring EMC in defence procurement. TÜV SÜD was an editor within the original MoD Def-Stan 59-411 EMC Working Group and has carried out development work in support of the Issue 3 update. There are a wide range of updates, of which some of the key ones include:
Part 1 Management and Planning addresses EMC throughout the project lifecycle and defines the documentation such as control plans, test plans and test reports. For COTS/MOTS (Commercial / Military Off-The-Shelf) procurement, a risk assessment procedure is provided that requires electromagnetic (EM) environment definition, evaluation of EMC compliance evidence (eg by gap analysis), determination of functional criticality of the equipment and platform and mitigation of unacceptable risks by remedial design, installation methods and retest. The MoD’s gap analysis evaluation tool has now been made available via the EMC Test Laboratory Association.
Part 1 Annex D has also been updated to include the latest guidance on compliance with the EMC Directive 2014/30/EU. Testing can be minimised by establishing technical documentation to demonstrate where Def Stan 59-411 satisfies EMC Directive requirements via gap analysis and ensuring that the remaining unsatisfied requirements are tested using commercial standards. The manufacturer or supplier then makes a Declaration of Conformity and applies CE Marking, with the option of assistance from an EMC Notified Body.
Part 3 Test Methods and Limits for Equipment and Sub Systems has been updated with new antenna port tests and changes to the radiated emission tests.
Previously, the land service radiated emission tuned antenna test DRE03 required the use of obsolete “Clansman” radio equipment in the frequency range up to 30 MHz. Commercially available active rod antennas can now achieve the required sensitivity and DRE03 has been replaced with a “standard” radiated emission test DRE01. Test laboratories will need to ensure they have active rod antenna that meets the performance requirement. The DRE01 test set-up for rod antenna has been amended and the rod antenna counterpoise must now be isolated from the ground plane bench, whereas previously it was bonded.
Antenna port tests were previously considered outside the scope of Def-Stan 59-411, but emissions can cause significant interference issues. The new antenna port emission tests therefore assess the contribution of unintentional emissions from antenna feeder cables and antennas when the radio is transmitting, on standby or receiving. The tests also apply to antenna power amplifiers. The new antenna port susceptibility tests assess the radio receiver performance in the presence of other transmissions. This is of increasing importance due to the MoD spectrum release and sharing initiatives, where military and civilian users must co-exist compatibly in the same frequency bands. Specialised test equipment is required for the antenna port susceptibility tests including low noise signal generators, filters and couplers.
Part 4 applies to whole platform and large system test and trials.
New updates have been made to the Annex B Land Service radiated emission tests. Radiated emission test DRE03 can be replaced with an equivalent test DRE01 using an active rod antenna over the frequency range 1.6 MHz to 30 MHz as long as precautions are taken to avoid overload of the antenna.
Part 5 provides design guidance with sections to cover air, land and sea applications, and addresses EMC fundamentals, equipment and platform design. There are no major changes to this part of the standard.