EMC EMI Testing

ITC India NABL Accredited EMC EMI Testing Laboratory. ITC India Providing EMC/EMI Testing in Less Than One Second Using Very Near Field Techniques


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We'll be talking about you see me in my testing using what's called a very in your field technique and we'll see that wanted and here is extremes the this each suffer so we're gonna do an introduction to very near field what does is turn me know how using it and then we'll show how we've actually implemented a system back into testing in the very near future will explain some other benefits that this approach and will go on to show how this very unusual testing can be used to give some protection the far-field or the chamber like measure results will show some other applications that are directly related.

EMC testing animal initial presentation so first of all am scan euro world-leading developer very fast you're in your field measurement applications this is based on an array of sensors that is happy approach rams tad this approach allows us to do real time measurement out the fields directly next to the device under test this real time testing can give understanding out that your children fax coupling distribution energy across the board typically these devices that can create are all pre compliance so even though they may get some protection up the chamber results into compliance devices they say array of sensors for the Turner Field there's actually two different product lines the first is it's called expert and this is the one that is related to your mind EMC testing this is the one that will be talking about this morning there's another application for this your Turner Field have been and that would be for antenna measurement the transmission to the park feel in this case is done very accurately an chi give results compare bill to the chamber this family tools called are expert okay so an introduction to the pair in your field people might be familiar with the concept of our field and near-field and the general concept is shown on this slide here began see in the center the device there's our earn the center up the screen is the antenna radiating in all directions and here we consider park field is given with some rules look down so these are approximations up to distance at which far Killy's might begin essentially this far field region is where the radiation pattern is kinda established no longer changing with respect to distance if you go within this region then we answer what's called be near-field inside in your field region the missions from the device are still and tracking strongly you're getting constructive and destructive interference causing the field to change very rapidly over short distance inside this bridge inside is near children is actually two different sub regions the first is the radiating your feel so this is where the energy at the state device under test be in an antenna or circuit court so it will eventually go into the parking region but it just hasn't had a chance to set up and establish the field inner our field conditions so that radiating near-field region is again given by some rules are I'm here so these are approximations.

Where it is distance might be from the device for testing land of course is the Wave link and it D in the D squared is the largest dimension you're relieving source now also in the Near Field there's an area where the fields are not a state from the device but there's actually stored energy this is called the reactive region and only the reactor region is a place for you wouldn't want to put a measurement device because you're disturbing those stored fields you're actually changing the device under test itself now what we found is I'm you can actually go into this region and get very good measurements I'll distribution up magnetic field so for antenna testing this is quite critical you have to account for these changes and and essentially do a correction in the EMC testing will see is

I'm essentially the magnetic fields a pretty stationary her static even when we place this data in this region so we can get good measurement out the the field and hence the occurrence which created those fields and this will allow us to essentially visualize on the PCB level what is going on in terms of induced currents are couple current or 'em hot races that kinda stuff so as an alternative to the very near field of course we have various far field measurement techniques comment on here is that to go into the chamber image echo chamber am this is of course what we're trying to emulate or at least a this is what we're trying to measure at the end of the day I so we'll see that as an option to this we can go back to the very near future uncertain measurements and effect later on and presentation we will see that we can get very close to this type of measurement just from the very near field results themselves now of course Turner Field measurement itself is not something that we a invented a dance and many people are you doing this if you have a hand-held probe you are completed very close to the device is your testing and essentially be in that what we call beer in your field region the difference is that hand-held probe typically is made very small so that it doesn't influence the devices testing and the downside is of course that its very slow move that program on and I am essentially sample all field in the different areas would take a long time I'm but if you went through this process if you did capture all those all these fields it is possible to essentially recreate what we call far fielder chamber test results of course during your field itself is the root cause of all those missions that's why century once you have that information

you can do that transition to the park field to do this the sense that we need a mechanism for during the transformation and that's for me for tonight extrapolation now look at a beer in your ok implementations or something that actually test in the Turner Field and essentially this is the basic technology so I mentioned before that we have an array of probes you can see here is actually over , probes in this array each one been essentially and your field probe very similar to
I'll what you might be familiar with us hand-held probe difference here is that Utah you no longer stand that single probe what we do is we disclaim China the switch that array capture all the field over the entire measurement service and sub-second time each these probs is a magnetic field pro so that means that were sent in magnetic field very close to the device and you can see in terms of frequency ranges am sense they can run from Cal herds all went yards now that limitations out the probe array is it the probe spacing is fixed will see that that is a limitation for am essentially the switch to rate technique but we do have been mechanism that can overcome this limitation and essentially reduce the resolution down to fraction a millimeter SEC your so we just seemed the got array of sensors the way this works in a system is battery is actually a pass a parade so there's the probes arranged in a and actually a great over the surface and those probe simply couple the energy and feed them into a spectrum analyzer the spectrum analyzers connected to a computer or Randy im expert software and there's a small adapter held and synchronize the switch in approach and the triggering a spectrum analyzer to the combination to the system is essentially what does the entire near-field mission what's good run some scans

what will identify from the device for testing is a special mission so essentially this is the same that you would measure with a hand-held probe or this essentially the same frequency that you wouldn't act if you put your device into a chamber so at this point we're just identifying the frequencies better coming from the device merle we are measuring in the very near he also the level up these measurements cannot be directly related to the chamber at this point but with one identified frequencies however we can go and do but we called a special mention and this is really where the true value of the near-field array comes into play you can see that at a given frequency

There's actually I'll distribution of that energy on the circuit board itself in this picture we're looking at the energy from a single frequency let megahertz which happens to be the fundamental frequency overclock honest as I'm and you can see where the source that the emissions is next to this crystal we can see how the energy goes into micro controller right next to the crystal but we can also detected that energy is leaking out into other areas are the board we can actually see the past that energy is leaking through allow us to understand the coupling mechanisms and also the mechanism that this might really in the far field causing EMC your ear mite problem so you can imagine if you had access to the type that information early on in your design cycle this is gonna tell you exactly what it is that you need to address in terms of layout changes or other investigations I'm hopefully long before you actually take this is line into a chamber and realized that Thursday design problem so what we're gonna do is actually very quickly switch over from these presentation slides over to the software I have the system set up next to me and what we'll do is do a quick test on the scanner saloon taxi in real time how quickly the system can work right now

We're looking at this offer interface for the metric system I will open up a special scan we go to the seventh year will be able to see that it will be measuring from Penn megahertz fixed resolution bandwidth so mister SKN turn on the device under test in and what we'll see is who quickly go through and do the spectral missions that this the score so we can see that is identified several strong signals let megahertz thirty three megahertz of course all harmonics losses from lower level signals investments as well now what this does is it identified with frequencies we have to you perhaps analyzed further a given that you detected saying let makers signal will do is open up a spatial scan and already set to megahertz . in fact to make sure that the stand herbs go over the entire scan area and you can see to make the selection approach easier and actually imported can file for this design I've imported a Gerber file you can also do a Jay pag if you don't have access to that to the cat I'll see can simply take a picture your device so in fact we'll do is we'll brunnette continuously and what that'll do is allow us to make changes to the device and in real time see what the I am what the effect is sorry your okay so what we're looking at is the spatial distribution of energy on this board as a changes in real time so on this board we also happen to have a small capacitor substantially decoupling capacitor I'll take that out Treacy were too much there and when I'm gonna do is fix the scale so religious to highlight real time aspect to this test system as it could be pass your back in we'll see immediate drop up in your field missions to of course are you with the solution to those missions was in order to drop by over DB

When you're working your lap you may have to do much more Tryon air the nest actually find the real true cause and the solution but you can see that essentially as quickly as you do you make any changes to your design I'm you can evaluate what effect that has on your annual emission levels okay I'll just stop I'll go back to the slights so can I was just a quick demonstration you can see in just a few seconds we're able to I am list a few seconds we're able to could be measured the device under test okay now will do is just go through some other benefits so we've been using this type of scanner for many years many of our customers at your house key back will be able to see exactly how this can be used in practice so the first one is changes in real time I am just as we saw their if you are making changes your design or if you are I am may be changing the functional aspects I may be different operating motor for more changes as soon as you make any change your device

He can very quickly evaluate the effect that has based on your show missions the other way that this is a benefit is in terms of internet events so if you have I'll maybe in a mission problem and you can trigger reliably what you can do is set up the scanner to brunch tenuously and essentially trigger on that event capture I am an event does happen and then even if it happens for a fraction of a second will be able to capture some portion a bit and then slowly build up an entire picture I'll the event when it does happen so that will allow you to kinda get a snapshot up the all the energy where it's going when that attachment that happens so another stronger application for this to listen what we call AB comparisons so essentially if you have a device where you maybe done for qualification you have in your field signature is as well as a I'm a particle measurement and you start making changes your design for whatever reason may be obsolete parts maybe you want to do some cost reduction I am essentially if you can make those changes and verify that there's no of no change in the near field and you might have confidence to actually tell all by that bites and not go through the full testing procedure another aspect that might be useful as just in doing some sample up to production because you can do it in just a few seconds you can sample devices from the production line and just make sure that there's no all the issues final aspect that where you might be able to use it is in fault diagnosis so again if you have a Borders not working very often the component or the section that the design that's caused problems will also have a change in near field emission signature so if you have a baseline to compare against you can essentially placer new border your billboard on their do comparison and where you see large differences will most likely be the area where there's a problem example shown in this picture is a far faulty soldering I am job on the RF trace chart the customer didn't know couldn't track down where that how many are chain was to the clipboard on here and they could see a significant difference in the emissions are frequency at this specific location you can also look at testing practiced effectiveness of filters first the ball um even bear find that your filter in the right location so you can see in this example we help our board on the right and you have the functional side equipment which the mixer and login and are
I was sitting on the left side and if we look at the Muirfield emissions you can see on the talk that eyes was generated in the power side and was coupling over to the a digital side and given in to the IRS section at this port so this can cause could be problems in terms of performance that the device as well as mission concerns now it is the verify that in fact energy was coupled across those power lines harriet was placed on there and you can immediately see I'll that was the proper solution it dropped the energy that escaped into the I am alongside aboard I significant portion now this may not be a production where the change although for some more runs that might be the best solution but it does indicate what is the change and it did validate are at least verified the under understanding that energy with coupling across those Pacific Alliance you could even take that further look at one line at a time shielding in and absorbers are an interesting one um sometimes when you're using shields what will happen is the energy will be reduced in that specific location because at the shield but the energy is simply redirected to another area board you'll have energy is keeping out radiated on another or the board him and essentially all you gonna displacer problem so happy now the ability to look at the entire board at a given frequency look at it in real time would immediately pick out whether or not you I am than a anything like just displaced energy in this offer there's also the ability to do essentially background subtraction so you can look at the plots in terms up the difference between two scans and essentially everything drops and leveled in your content

If you've made some small increase for maybe a large increase in a specific location at least director eyes open air and you can analyze that home Turner now we met can that be fixed spacing appear ready could be a limitation in some situations what we've done is we've developed actually a hybrid mechanical solution so thick that fixed rate and it will eventually put a small jitter on it just by fractions of a millimeter allowing us to create senseless synthetic high-resolution array and you can see what this will do is it can now take us down to individual trace level identifying specific years that there possibly coupling energy and you can actually track tisra different layers at the board follow where your energy is coupling through this I now so we've always talked about result in terms of near-field and you can see that it does have tremendous value in your field but it does require someone had a lot of experience in terms of analyzing the results and essentially making the correlation between what might be a complex problem and what they see in your show what we're gonna do is kinda highlight that concept little bit more with a simple case study just look at correlation between the very near killed in the far field essentially this will establish that link get confident that they can happen the you can look at the your field and make some conclusions but parkfield so personable we've done it just looked at essentially cockles wit ground plane problem and you can see when put in a chamber at various frequencies there's a significant difference when wanna the transmission lines goes across a split in the ground 

what we did and was a sin that the split hatcher main in  the design for whatever reasons and look at some sorta mitigation so we looked at combine those two grounds together either with a short or with a capacitive connection and we could look at various solutions and essentially what we did is make a judgment just based on your field so here we can see it in your field results I am where solid ground and then with the split ground and then you can see just a couple results have been shown here is an example but there's the jumper reconnecting us to ground in the center and the jumper reconnecting has two grounds the edge the center will be right anne the a the trades that going over that split which is shown here in and break bread colors with interesting is that from the near field itself you can see that the jumper in the center is have enough big improvement in terms up in your field levels and in fact the jumper it's placed at the edge up the board seems to make the problem worse so just from this quick near-field analysis we might be able to use sensually reduce the number samples are cases that we want to follow up on so it doesn't tell us whether or not any of these will after fail in a compliance test but it does tell us that if we have a split Graham problem and that cannot be identified in fact I am by looking at Muirfield as well it also tells us what the best medication might be so it doesn't tell us whether it's good enough but it gives us some further Ikea where to go in terms of a follow-up times okay so what we'll do now is will pick it up one step further rather than relying on the user to look at in your field and make those correlations with their basic understanding of you're chillin fax can we ask the software to make that step for us essentially do the correlation and the answer is that in fact can do that you can measure in your field and you can protect I'll the compliance level measurement now we use this quite extensively in the antenna measurement side out are company the difference on the antenna site is that we would have access to the phase information in your feel so in fact we can get very accurate estimations antenna measurements rated power and patterns in the ENC we don't have access to the face so there's a bit more uncertainty in terms of the addicted results but this is an example

where you can see with bats split ground problem the predictions are within about dB so this has been improved over time and with this software it now so that they can get within by DB up the chamber results now sensually the way that this works is you measure in the very near field with expert we export that near field data and with this software we do a correction for in your field effects which is no one we import ban into at their party software and they do the transmission in the modeling to provide those chamber approximations so that whole process takes between and minutes to run on your desktop with no other equipment required so essentially this is giving you I certainly wanted the cheapest in and also in the faeces pre compliance tools to sense they give you some confidence on whether or not your device is going to you I in fact pass or fail when it comes to the compliance testing

It is beyond just EMC is also applications for this fear in your field testing a good example would be in your field in tennis so normally antennas we would capture in our other product line but for near-field antennas are not acting in the classical sense really interested in in but the strength up the fields are next to the bystanders distances so you can see at . megahertz in a mobile home which had an your field antenna can actually capture those fields and display

I feel strange that right next to the device another paper testing is distortion or passive inter modulation test them so because the devices very sensitive and also very linear it's a actually quite a good tool for measuring at third a third harmonic distortion or some of these other things they're going to be very low with respect to the carrier so in fact in this testing what we're looking at is measuring out a very sent an S and those antennas are shown with their fundamental transmit power switch very strong transmit powers p.m. the system can measure those third order harmonics down to about minus GB with respect to the carrier let's love sensitivity and Lynn he really means that begin in fact use this for from fell for her parents testing so in this example what we're doing is we're looking at be near-field emissions from the device but not in a sense up a compliance test now we're looking at more in terms self interference or performance of your device so if you have self-generated noises that is coincident with receive frequency and obviously that's going to harm that receive your in this case we can see that noise was generated ap by gigahertz which happens to be right in the middle up the GPS pet since that noise is generated whenever we have the camera on you can imagine that the GPS performance for this device will suffer and every have the camera on so no understanding where that where the energy is created and also how our couples through the design and what every the design team to be upgrading strongly that might give you some indication a biter shielding some absorber or even redesigning the place the sensitive GPS receiver and area that isn't a really been quite strongly okay so we're almost done senseless we just want to look at I am benefits to the system and you can see this is kinda funny picture you can almost see the electromagnetic fields you can't coming down cable and leaving the system it certainly the string to the system are the real time P call capability for skiers events that the fact that you can measure in less than a second means that you have access to a new way of tissue devices

You have this trial Nair basis that's now repeatable reliable and sometimes a lot easier to do obviously this is not compliance data but with the ability of other software to now take that near-field give an approximation it does allow you to start making conclusions about whether or not your device will pass or fail by limitation that we see is we are limited little bit in terms up the structure the device obviously shop flat PCB's are a optimum for this type of testing if you have three-dimensional structures there is some limitation in every Ghosn certainly in terms up the test be and I am and ability to give info into design

We feel that there is certainly some value here for designers and even testers in the EMC now also point out before we end that I am a lot more information about and Dan Anyiam expertise available at the website there are white papers and case studies that where essentially distilled down for this presentation so PNM interest and following up with more details those are available on website thank you risk at thank you very much for your presentation before we begin our question asked answer session I would like to make a call for final questions please feel free to enter any last minute questions you may have in the navigation pane and hopefully we'll get to them in the meantime risque here's a question for you assume the colors in the spatial scan indicate institutes the mission can a frequency range be limited are filtered for this display that's right so the colors did indicate intensity I am on the right you can see that read well the most intense a blue with the least intense December scans that I discussed here and they showed in the demonstration work what we call single frequency stats however the software can run through a range of frequencies combine those result Heather giving you kinda a wideband a special a mission and further the software can then I isolate ourselves we slice through that area and you can pull out one frequency a time are you going to analyze a single cell in that device and look at the spectral missions based on location as well Kb risque can be used to test emissions a small assemble products um that's right so when we when we mainly look at the results here I was always looking at the Ross circuit board and that's because

We were mainly trying to push this is be early on in the design cycle looking at root cause problems by you can test of a lethal products I'm so in fact if you are in a plastic enclosure essentially they'll have no effect on the emissions am if you're inside metal enclosures or some sort of shielded enclosure am what you'll see is not the board level missions but you'll see a mission come you noticed seams and gaps in your device if you have cabling net connect your device I am we might also pick up emissions are the currents that are happening along that people so you can I am measure fully assembled devices as well thank you very much here's another question for you when testing at the very near field to ambient noise still distort the results can the ambient noise be distinguished from noise from the unit under test yet what he saw from the to the thing that I did hear time dissident our meeting room I'm so weird completely exposed and environment and we didn't see any background noise all the emissions that we picked up were from the device under test you can of course they were backgrounds dance to verify that now there is some situations where you will pick up ambiance signals if you're trying to be very sensitive doing very sensitive measurements the globe and let and you can with external I'm amplifiers in the past up the system it's possible that you pick up ambient noise say and radio stations or sell bans were there is strong signals in that type of situation I am you can do that backgrounds can insert track and I hope for your from your testing or you may be required to go into a shield environment in that case okay another attendee asked if the Dutt it kept upside down with the pattern change yeah that's an interesting question so I am for something like a two sided design I am essentially the top and the bottom will look very similar I am if you have multiple ever multilayer boards on and the internal either ground planes or power coins act as good shields for the EMC measurements

You will see a different from signature on it hard and on the bunker device so am if that's the case what you can do is flip over that product a measure both sites but not a problem what one further point to this is that I am on a multi-layered design at the internal layers that the Board may also be conducting energy now those ones I'm especially at higher frequencies where the ground plane is a good shield those cases we can't measure what's happening internal to the board but if you think a bit those line alsoare not contributing to anything to do with the emissions from the board to wear those internal layers become a concern might be at gaps in the shield you the add to the board or when they transition to some in the surface layers and in all those situations who would then be able to pick up emissions but after that whenever that occurs thank you risk a another question temi testbed measure both ET and H
feels or is it H feel only where a field is derived yeah right now this can only measures the age field so it is possible to translate to the you field although in the reactive region that's a very difficult problems so we simply perfect present the H field results in the software and what that essentially correlates to is the on current on the board so for board level now since the age fielder's is probably sufficient for doing the transformations to the far field I'll you can see that having only one of those components probably impact the accuracy I'm to some degree as well okay great one more question here had you calibrate the single probe so in fact ironically that the single probe is I am is in the array at least be individual Pro can you raise calibrated with a single probe so we will use actually that hand-held probe technique we have a robotic positioner which will move a single probe over every element in the array and very accurately position that single probe so that we can in fact measure from the response every single pro and that dude is essentially our calibration data so we know not just the hope response but also all the internal losses inside the scanner so when you turn on what we call probe compensation in the software essentially all the variations from manufacturing or from differential power plants are taking into account so that fields are then given very accurately at probe location

we're almost out of time we have a couple minutes left so I'm gonna ask another question I wanted can I'm thank our audience for getting fabulous questions coming in and we'll continue to feed them as we can with the time allowed risk up for you what level of sensitivity can be achieved and how would that translates adp microvolts premier at three meters okay so we we saw the ones like that touched on the sensitivity and we also mention this when we talked bout the defense herself in return problems um the way we've characterizes sense to be in that case I am is a little bit different and we've done in terms of the conducted power in a microstrip so if you have a conducted power in your micro strip a minus a hundred and DBM will be able to detect the magnetic fields from that I cruise ship now it is a little bit frequency sensitive so it's not it's not that sensible frequencies but it gives me an idea that you can pick up the fields from extremely low level I'm conducted energy in terms of the  EMC or compliance testing this is many orders of magnitude lower than any sort a mission that would cause problems in compliance setting so defensively near-field can't be directly translated to a I'm voltage at in a three year test setup but if it were even close to failing in their in that chamber I will call you bout to sixty are are more DB more sensitive than is required to pick that up in your field thank you at risk we perceive so many thought provoking questions more than we can get it today it's our time is up but I will ask that you please refer back to the event site we will post answers to all these inquiries bresca will be providing the answers for us please feel free to email us at info at ITC India dot comwith any more specifics and will direct you accordingly also be reminded that our recording the weather now will be available on our website next week and a link will be sent directly to you I thanks again to risk a first time today and the time he will take in answering your question and to you for attending don't forget to check the website for any additional webinars around tables you would like to attend this week www.itcindia.org again thank you risk a Cell match thank you