EMC precompliance testing setup

[kmoonwalker]

from experience:

product usually passes in traditional sweep approach (if no erratic occuring peaks will exist during given freq sweep stage to show up and this means it would most probalby pass in testing lab too


RTSA approach is very nice especially on prototype stage when you wanna see problems occuring when you simply touch and move some internal interconnect cable, etc but you have a good point there so it is being done in following way:

you analyze some limited range not the whole range and then go range by range adjusting them as you need cause you may miss some things with wide band

after some time spent on certain prototype you will know which areas of freq range you need to look at making corrections, adjustments

and then after all done you still need to go back to multiple sweeps to be certain no one will later hunt for you 

[tszaboo]

With a Power amplifier and the tracking generator of the SA, and TEM cell, it's apparently possible to do some immunity testing. This would only need the power amplifier as the extra part.
Well, and a coupler to monitor the RF output.

For immunity testing you'll also want AM modulation. An electric field probe to verify the electric field strength is also nice to have but in a TEM cell you can calculate the resulting field strength from the input power and geometry. Don't forget a load capable of dissipating the amplifiers power. I opted to buy a 5W 20dB attenuator (a good quality one!); the attenuator can also be used to measure the transfer characteristic of the amplifier itself.

In my setup I measured the amplifier's frequency response at several power levels and created a calibration table. The table is used to control the power level of an RF generator (in my case an R&S SMIQ) to create the desired field strength through my script. There are also dwell time requirements for immunity testing (DUT response time to events). All in all I'm not sure a tracking generator on a spectrum analyser will do much good. You'll need software to run immunity tests because they are too tedious to do manually. From all the EMC tests, the immunity tests take most of the time. Count on at least 20 minutes per run.

Personally I like to test products up to 30V/m. For consumer stuff the limit is 3V/m but that is too low for flawless operation in the real world in my experience.

True AM modulation is required, I'm looking the Tekbox TBMDA5, which is an AM modulated amplifier.
They claim that about 200V/m can be reached in their TEM cells. And their software sets up the SA to do the tracking generator output, and the amplifier does the modulation. If it all works as plug and play, I would be really happy.

RTSA approach is very nice especially on prototype stage when you wanna see problems occuring when you simply touch and move some internal interconnect cable, etc but you have a good point there so it is being done in following way:

Having the RTSA is useful for the software guys for timing analysis, or to see individual messages.
Or if we cannot set up CW, because it would kill the battery for example. I think that would be a real pain point, I'm not even sure I can transmit continuously on smaller devices, the secondary ESR of the built in battery would kill it.

[kmoonwalker]

for that especially but myself I was referring to probing with "wand" some problematic prototype PCB

[kmoonwalker]

I think you should reach out to Tekbox and check out their software, find out what suits your needs and then select the hardware compatible with it (or recommended for it) and within your budget

There are also other options like Keysight or Rohde Electra but usually way more expensive

[scottapotamas]

Thanks, good to see that others have similar setups. I'm leaning towards the RSA5000N because of the EMC is included by default. On the other hand I can see the 3rd harmonic of the 2.4Ghz on the Siglent's 7.5GHz bandwidth. Decisions, decisions...
I think I'm fine with some spurs in precompliance testing. If it goes above the line, I have to investigate it anyway. I'm reading that some of the QP measurement, the low frequency ones, could take 4 hours to perform. That's a problem because that's a whole day gone for one test, I might need to do it in two orientation of the DUT and Antenna... I would rather spend my time on better things.

I'm trying the EMCview in demo mode. They have separate limit lines for average responding and peak filters? That sounds very useful.

To be clear, those spurs aren't in swept mode. I don't know how the pro version moves the real-time span but you'd get that spur/noise floor in every window that it's sampling. It's quiet enough it'll likely be drowned out by ambient and DUT noise. Just making sure you're aware beforehand.

On frequency, LISN's aren't useful above the low hundreds of MHz range. My RF current probe tapers off under a gig. TBTC2 is something like -15dB at 3G which is where my RSA stops. More bandwidth is something I'd want given my workloads intersect with relatively fast interconnects more often but that's the broader usability of the tool moreso than pre-compliance.

Even the RSA's internal EMI app has QP and peak limit lines in the library, can draw 5? at once and so that's not unique to emcview or other test software. Slightly more tedious to setup but not a huge issue once you've done it a few times. For business use the look/feel of emcview's documentation is worth it over Rigol's exports, no experience with other paid options.

It's rare for me to run a single scan longer than 10-15 minutes during prototyping but when I've done a 'last check' before testing some of those scans have taken most of an hour, diminishing returns etc. The test house uses a ESW26 and they can get similar feeling results in less than a minute.

Happy to throw something in the TEM and give you access to the VM that runs the software to play around if you want.

Having the RTSA is useful for the software guys for timing analysis, or to see individual messages

IMO pretty limiting on the Rigol you're probably better off with any SDR for that.

[tszaboo]

I think you should reach out to Tekbox and check out their software, find out what suits your needs and then select the hardware compatible with it (or recommended for it) and within your budget

There are also other options like Keysight or Rohde Electra but usually way more expensive

Their software can be run without a license up to 10MHz or something. All the files for their equipment is there.
There is a local store, Eleshop, who seems to carry their lineup. Also Batronix.
Looking at their lineup, they seem to have a complete solution at low cost, including the software.
My plan is, we buy the accessories, and get a loan of 2-3 different SAs from them, and buy the one that's the most suitable.

On frequency, LISN's aren't useful above the low hundreds of MHz range. My RF current probe tapers off under a gig. TBTC2 is something like -15dB at 3G which is where my RSA stops. More bandwidth is something I'd want given my workloads intersect with relatively fast interconnects more often but that's the broader usability of the tool moreso than pre-compliance.

I don't even need a LISN right now. I throw it in the basket, because it's easier to buy it at the same time rather than to come back in a few months realizing that we need it. In the middle of a project.

IMO pretty limiting on the Rigol you're probably better off with any SDR for that.

Interesting

[kmoonwalker]

your plan is good

Also as mentioned by others - you need to be careful in terms of noise levels suitable for you

Often happened that some ancient Rohde had less noise than some new of shelve chinese options (they are generaly not bad nowadays but one needs to pay attention in some cases). if you were limited to 3 GHz I would say to try out  FPC-COM2  + EMCVIEW PRO software (you also need the pro for real time analysis on Rigol etc but it is like 699USD or something). Rigol 5000 series also has good opinions but I had no possibility to test it myself. Next level of Rohde starts like 20-25k euro and it requires a lot of extra money to make it reasonably equipped so I would recommend to browse some offers with preowned not very old models (they are usually with options so lots of savings even on that aspect alone). Fast, good Siglent analyzers are also expensive. Cheap ones are not bad but same as with Rigol pay attention to noise.

If you say that you do not have a problem with customers requirements I say lucky You that you can go on with whatever fits you

Some are having orders with production quality tests on selected equipment from DMM (with cal and adjustment certificate valid) to other more fancy things with especially written procedures for their software that customers are providing and they demand reports for each production stage to asses the quality of adjustments, etc.

Times of whatever goes are in the past in 90% of cases and those with low expectations are usually problematic with payments :/

[jc101]

I wish they would incorporate support for the Signal Hound BB60C into EMCView.
I asked them around a year ago, but they said they were too busy. The Signal Hound Spike software is excellent, but things would be easier with a dedicated front end like EMCView.

[kmoonwalker]

yep friends of mine also had that reply multple times about other analyzers :/

[tszaboo]

Looks like I've got the budget for the test setup, just wrote the email for the RFQ for the shop. I ended up with the Rigol RSA5065 in the end. It was significantly cheaper than the equivalent Siglent together with its options.

[tszaboo]

Yesterday I unpacked most of the things for this setup. It's interesting, did some initial tests. So without having a proper Anechoic chamber, I got of course larger emissions than industry standard limits like CISPR 11. FM band the background noise was high, somewhere in Band 8 of LTE, so around 850MHz the noise was high, sometimes we got a large peak here and there. It wasn't really hopeless, I think the directional antennas help a lot, or we got lucky at the location.
We forgot to buy tripods to the antennas, that are also quite big and heavy. And the cables we bought had rubbish connectors, some better cables are needed.

I plan to re-measure some of our previous DUTs to verify the setup. Interesting times.
The Rigol RSA has quite a lot of features. I didn't like hat they were calling a few things differently, I guess this is more about learning and expectations, and getting used to the menu, rather than making a judgement.