Rohde & Schwarz Demysifying EMC 2019

A fantastic day at the Rohde and Schwarz Demystifying EMC 2019 show down at Silverstone. It provided a chance to reconnect with some familiar faces and meet a whole load of new ones. R&S always put on a good event with varied content and lots of interest.

I was presenting a talk entitled “From Design To Pre-Compliance: Pitfalls and Pro Tips” which received lots of positive feedback from the attendees.

The weather was glorious with bullet blue skies and The Wing venue in the centre of the circuit makes for a great location.

The Unit 3 Compliance stand was very popular throughout the day with a queue of people stopping by to say hello and talk about pre-compliance testing.

The Pocket EMC Debug Probes flew off the table too.

Demystifying EMC 2018 – Silverstone

Rohde & Schwarz held this years’s instance of their excellent Demystifying EMC seminar at the Silverstone race track in the Midlands. The venue was right in the middle of the racecourse with a great view of the start/finish straight.

It was good to see so many meaty sounding technical EMC presentations on offer and my only regret was that I couldn’t split myself into two or three and attend them all. Instead, I’m going to have to wait patiently for the PDFs of the slides to come through.

In the meantime here’s a quick rundown of some salient points from the presentations that I attended.

“Practical Probing Techniques for EMC Troubleshooting” – Lee Hill, Silent Solutions

Given the relatively short amount of time, Lee gave a very condensed presentation of basic EMI issues encountered, the need for probing and the merits of different types of probes available.

He included some good explanations on the figures of merit for RF current probes and gave a compelling argument for the use of a pre-amplifier with a near field probe: “it makes all the signals look important!”

The only small disagreement I’d have with his otherwise excellent talk was his recommendation against making one’s own near field probes. I think that, with some consideration and research, it is possible to make probe sets that are just as useful as ones you can buy. I frequently use a home made capacitive field probe for debugging and actually prefer it to the one from my purchased kit. However, having the luxury of an anechoic chamber, I’m usually using the probes to chase a known frequency. Therefore I’m more interested in relative sensitivity rather than absolute calibration as I’ll already have some comparable absolute levels from the chamber.

If you get the chance to see Lee present I can highly recommend attending.

“Technical Documentation for CE Marking” – Stuart Aust, Horiba Mira

Stuart gave a brief run down of the Technical File requirements and I was pleased to find out my understanding of the requirements was aligned with his.

“Risk Assessments Required by the EMC and RE Directives” – James Daniels, Element

The EMCD and RED come with a requirement for manufacturers to complete a Risk Assessment and James gave a thought provoking presentation on how one might go about this.

Interestingly in future harmonised product standards, the Annex ZA/ZZ part will give information on what Essential Requirements of the directives that the standard gives a presumption of conformity to. This will take a while to filter into the mainstream, especially given the sometimes glacial pace of standards publishing and vested interests within standards committees.

Again, it all hinges on how comfortable a particular manufacturer is with the concept of risk. Sometimes, as EMC and standards professionals we often apply things rigorously when such an approach might not be required from the manufacturers standpoint. This is an issue I’ll be coming back to in a future blog as its something that most people probably don’t already formally complete or even consider. I shall be advising my customers on how to best complete these requirements in the future.

“Assessment of modules and EMC testing of non-radio products which include a radio module” – Michael Derby, ACB

Michael gave a thorough and practised presentation into the requirements for integrating radio modules into existing products, from the perspective of the FCC and the RED. I was pleased to find out his talk confirming my understanding of the process.


After receiving copies of all the other presentations, some things that stood out as particularly interesting were:

  • Real time spectral analysis for EMI debugging. I miss the real time analyser from my previous employer when I could prise it out of the hands of the RF department. I’ve had some success with replicating this using a low cost pre-amplifier and Software Defined Radio (SDR) but its not a patch on a proper instrument. The usefulness of a large real time bandwidth and good user interface is not to be underestimated and I’ve found several intra-system (platform noise) based problems using this technique.
  • Langer presented a really good look at the physical basis for radiated emissions from PCBs. I’ll be studying these slides for future ideas into debugging emissions! They also had a demo in the exhibition hall of their miniature noise injection pens which I’d be very interested to trial in future.
  • Wurth have some dense and interesting looking info on filtering for DC/DC converters. The broadband noise from these can be quite pernicious and often ends up making its way out of poorly filtered unscreened power cables.
  • Albatross Projects gave an update from the CISPR committees responsible for various product standards. Points of interest were EN 55035 making onto the RED list of standards and some small changes to test equipment for EN 55015.
  • Rohde & Schwarz had a good primer on requirements for the Radio Equipment directive from the radio testing perspective. Given the vast range of radio test equipment they make it was no surprise that this featured and who can blame them!
  • Michael Derby (ACB) also had some slides on the RED and the state of various ETSI standards. There was a wealth of info in this presentation so I shall be going through it in some detail.

All in all I was most impressed with the technical content at the seminar and will certainly be attending future events. Thanks to the Rohde & Schwarz for putting on such a good event.


An Important Balance

Here at Unit 3 Compliance, we recognise that the industry we primarily work in, electronics, has environmental consequences caused by the production, use and disposal of electronic products and systems. Many electronic components are highly complex and not easily recyclable. Energy usage of electronic products is massive. Waste electronics, if not disposed of correctly can cause an environmental hazard, never mind the associated plastics and other components.

We only have one planet to live on, to pass on to future generations and we feel strongly that we cannot shirk our responsibility to the environment. That said, the ability of an individual or small organisation to make significant changes to society and the environment is difficult. We have taken action to try and redress the balance and to attempt to lessen our impact on the environment.

We try to minimise the amount of waste we generate but, where we do, as much of it as possible is recycled. Given the amount of tea we drink, this adds up to a lot of composted teabags!

We have moved our electricity provider to Ecotricity who reinvest their profits into building windfarms and bio-methane mills.

Most importantly for us, we have become a member of 1% For The Planet. In doing so we have committed to give at least 1% of our sales turnover (not profit) every year to environmental charities who are on the front line of trying to make the planet a better place. Reading Yvon Chouinard’s book “Let My People Go Surfing” that tells of his environmental commitments as CEO of Patagonia Inc. was a significant influencing factor in this decision.

We look forward to playing our part.

log periodic christmas tree

Have an anechoic Christmas!

The office tree is up!

Wishing all the customers, suppliers and friends of Unit 3 Compliance a very happy Christmas and a prosperous New Year.

“Oh Christmas tree, oh Christmas tree

Your branches grow,

Log periodically…”

log periodic christmas tree

Antenna Miniaturisation

An article just published on Nature Communications covers some interesting and quite exciting developments in antenna miniaturisation.



Electrical antennae rely on being resonant or partly resonant with the electromagnetic wave at the frequency of interest. For a dipole, a length of lambda / 4 is ideal but antennae can be designed with electrical lengths down to lambda / 10. The technique of antenna construction shown in this research means that effective antennae can be constructed that work at electrical lengths of nearly lambda / 600.

If you take a 950MHz (mobile phone low band frequencies) full dipole it will have a length = c / (f * 2) = 16cm. With this new technology, this antenna length could come down to sub 1cm distances. This decrease by over a factor of 10 is highly significant and with the application to sub-resonant antenna designs, further decreases in size could reasonably be expected.



The technology itself is very clever, sandwiching a layer of piezoelectric material (voltage to mechanical movement) with a layer of ferromagnetic material to form what the paper refers to as a “ME heterostructure” (I prefer sandwich… mmmm… sandwich). The magnetic part of an incident EM wave causes the ferromagnetic layer to change shape in response. In turn, this makes the bonded piezoelectric layer change shape, creating a voltage on the output terminals. The process of reception is now mechanical rather than electronic with the tuning of the antenna primarily performed by selecting the materials based on their mechanical properties, thereby tuning the mechanical resonant frequency.

Similarly, applying a voltage to the piezoelectric material will change its shape, causing the shape of the

It’s worth taking a step back to point out that you can perform a similar trick with a conventional antenna by increasing the dielectric constant of the surrounding material. This changes the speed of light within this medium which is dictated by the Velocity Factor (VF) = 1 / sqrt [Er] (where Er is the dielectric constant or relative permittivity). This is why placing your antenna closely coupled to a plastic enclosure can change the effective frequency. Two downsides that make this approach less useful for antenna miniaturisation:

  1. The range of dielectric constants of insulating materials. FR4 PCB material is typically around 4, silicon and alumina can be in the 11-12 region. Higher values for liquids or more exotic materials do exist.
  2. The square root term around the dielectric constant causing the reduction in VF to become less significant with increasing Er

The mechanical “stiffness” of the new antenna (analogous to dielectric constant) is suitably high that the resonant wavelength is much smaller in the materials used leading the the significantly smaller antennae producible using this technique.


CMOS Process

What is even more exciting is that these new antennae are produced using a CMOS process (detailed in the supplementary material).

This means that integration of the antenna and receiver could be integrated onto the same silicon die in future. Not only would this make things ridiculously compact but it would also allow the receiver circuitry to be placed electrically right next to the antenna which could reduce coupling of noise and improve sensitivity.

It also gives the scope, as mentioned in the paper, of being able to print arrays of antennae on the same die. This could be used to make compact phased arrays, wideband arrays or just the key antennae for different frequencies required for a mobile communications device.

IoT (the favourite industry buzzword at present) solutions will get smaller, cheaper and easier to integrate, perhaps leading to a further connected-ness revolution. The potential impact is fascinating.


Magnetic Coupling and the Near Field

Because these antenna operate on the magnetic component of the EM wave, it should make them more efficient when operating in the near field.

Original image can be found here.

The near field is the distance between antenna and source when the ratio of distance to wavelength is below the ratio of 1 / 2*pi (see above chart). In this region, the impedances of the magnetic and electric fields are not related by the impedance of free space (approx 377 ohms). The field from a magnetic dipole decays with the cube of the distance (not the square) so being able to place a small magnetically sensitive resonant antenna closer to the magnetic field source provides a new method for sensing small currents right next to the source.



The decrease in size could lead to problems in the capacity to handle higher transmit powers or currents. Having said that, the thermal coupling of the antenna to a solid material should be good meaning the thermal resistance of the antenna to ambient could be both quite low and controllable.

Magnetic materials have other characteristics such as saturation and hysterisis so it will be interesting to see how it handles large DC or low frequency AC magnetic fields caused by electrical power wiring. I wonder if this will mean it gets classified as a magnetically sensitive component and starts to fall under the remit of IEC 61000-4-8 testing for such things.

Having worked on designs involving high voltage differential piezoelectric transformers below, I know that they require careful mechanical handling as they will chip, crack and break if treated roughly (although, probably just as much as ferrite of the same dimensions). Conventional metallic structure antennae are generally quite robust or can be made so. I believe the small mass and the encapsulation of these antennae in a plastic or ceramic package could well solve many of these issues.

This also presents the possibility of mechanical interference to an electrical signal. I don’t have a handle on what sort of high frequency mechanical vibrations might exist in the real world and I can imagine their energy would be quite low at the really high frequencies with elasticity of materials starting to take over. I can imagine trying to debug an RF sensitivity issue with a stethoscope for a change!

The technology website Futurism speculates that these could form the basis of a brain-computer interface. Needless to say, the EMC immunity applications of such a technology, especially in our increasingly “EM-dense” environment would be of massive concern. Perhaps we will be seeing the imminent return of the tin-foil hat as a genuine reason for keeping the government out of your brain!

You can read the full article here.

Header image taken from the original article.

We Are Opening!

Unit 3 Compliance is a new West Yorkshire based EMC design and test consultancy. It provides a unique service of engineering led EMC test support for your products through the entire design cycle. We know that meeting EMC requirements can be a challenge for companies without their own test facilities or in depth experience which is where we can help.

We are pleased to announce that we are opening our new HQ and EMC test laboratory in Bradford, West Yorkshire. Easily accessible from the M62/M606 we are well placed to serve companies across the north of England and beyond.

As you can imagine, installing all the necessary measurement facilites, such as our 3m anechoic chamber, takes some time. Our EMC test lab is in the process of being commissioned and should be open for testing services from Monday 5th June 2017.

However we are not just a test lab. We provide design support and consultancy services for your products to help you to meet whatever EMC requirements you may have. These services will be available from Monday 24th April 2017.

We are looking forward to working with you, helping to solve your problems, and getting your products to market as smoothly as possible. So get in touch and let’s get started!