Power line filters safeguard EMC test chambers

5th September 2022

MPE Ltd

Sam Holland

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In most situations nowadays, systems must be available 24 hours a day, seven days a week, and operate safely and securely without any interruption in service due to interference. That is no more so than in the universe of EMC test chambers. Such specialised chambers test electronic devices against regulatory standards applicable to both radiated and conducted radio-frequency (RF) emissions and immunity. MPE discusses.

This article originally appeared in the August '22 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

Various forms of RF regulations and test & measurement may be applicable to anechoic chambers for antenna testing or for automotive NVH (Noise, Vibration, Harshness) and performance testing – or indeed the world of satellite communications and broadcasting.

Accordingly, integrated high-current MPE filters provide essential EMC protection for incoming power lines on RFI-shielded test chambers designed in-house, manufactured, and installed by NTD Shielding of St Helens, Merseyside.

During 2019, NTD Shielding Services installed and commissioned a high-performance RF chamber for the BBC. The high-performance chamber measures 2.4 x 2.4 x 3.6m and incorporates a full electrical package with fibre-to-data conversion. Within this system MPE filters were vital to provide protection and Power line filters safeguard EMC test chambers electrical immunity for the incoming power lines, a Vesda fire detection system and a ‘test-in-progress’ status warning light.

MPE’s EMC filters were specified to ensure the high efficiency of the RFI shield and also the EMC compliance of the whole electrical system and each of its incoming lines. The power line filters manufactured by MPE for this application provide 100dB of insertion loss performance across a full frequency range extending to over 20GHz. A variety of MPE filters for up to 32A current were required to meet the demands of the application.

In another set of applications, NTD Shielding Services installed three bespoke chamber solutions for Isotropic Systems at Reading, each incorporating MPE’s high-performance EMC filters.
A pioneer in the satellite communications market, Isotropic Systems has a host of ambitious new satellite constellations from SES, Inmarsat, SpaceX, OneWeb, Telesat and Amazon currently being developed and deployed in conjunction with GEO HTS assets. Central to these development programmes, Isotropic required a high-performance in-house EMC testing capability as a critical resource.

NTD Shielding Services installed the three bespoke chambers between January and March 2020, with commissioning completed shortly afterwards. In support of these works MPE supplied a range of its high-performance filter solutions, including extended performance variants which provided high levels of attenuation through to 40GHz.

The first chamber at Isotropic Systems measured 4.5 x 9.5 x 4.5m, featuring double access doors, access ramps and fire detection systems, with integral 16A and 32A extended performance filters from MPE. Measuring 3.5 x 10.5 x 3.5m, the second chamber was equipped with semi-automatic pneumatic doors, USB ports, a media conversion pack and fire detection systems. Again, MPE’s 32A filter solutions were utilised.

Completing the installation was a 40GHz ultra-performance, millimetre wave, mobile chamber, measuring 1.3 x 2.8 x 1.3m and incorporating MPE’s DC filter solutions. MPE’s EMC filters were specified on all three applications at Isotropic Systems to ensure the high-performance of each EMC chamber and also the EMC compliance of each electrical system and its incoming lines. In this case, the power line filters manufactured by MPE provide 100dB of insertion loss performance across a full frequency range to more than 40GHz.

Among other test chambers in current service in the UK which incorporate MPE protection solutions are those for the Microwave Vision Group (MVG) and Horiba MIRA Ltd.

NTD Shielding installed radio-frequency chamber for the BBC, Shepherd's Bush.

At Horiba MIRA in Nuneaton, Warwickshire, MPE upgraded the protection on a chamber to meet the requirements of the electric vehicle market.

MPE delivered both AC and DC filters, with the DC filter providing a very high attenuation performance of 100dB from 10KHz through to 18GHz and being rated for 800A at up to 1,500V DC. Whilst the chamber itself measured around 20 x 11 x 7.5m, the available space for any new filters was of primary concern, as was the overall increase in weight to the existing structure from the filters.

MPE therefore adapted designs from its high-current DC filter catalogue range, ensuring that envelope size and weight limits were met. MPE also designed and delivered custom busbar configurations and custom enclosure hardware for both external and internal mounting to the existing structure. The result was a smooth and efficient filter installation, minimising the need for MIRA to make changes to its existing chamber.