Any EMC Engineers out there? n00b here and need some tips.

[guscrown]

I recently been doing some EMC work for the company I work for, along with many other design activities. Are there any EMC experts out there that might want to share some tips, tricks, literature, tutorials, etc?

I really hope to find some of you out there.

[jahonen]

Are you after emission or immunity tips?

The only general tip one can give (all boil down to this) is to constrain your current loops as small as possible, also the invisible unintended ones (which cause all the EMC grief).

Regards,
Janne

[Simon]

you'd have to explain exactly what your trying to do. Where I work all they know about EMC is to buy an overpriced filter and put it on all inputs and outputs

[Neilm]

When I started having to learn about EMC I found this site. http://www.compliance-club.com/

It has lots of articals about PCB layout and circuit design for EMC compliance. One of the major contributors is  Keith Armstrong. His articles are simple to follow and are not physics heavy. I learned a lot from these.

Yours

Neil

[tyblu]

I was recommended this book: http://www.amazon.com/gp/product/0470189304 , and it is coming on Thursday . There is one app note that was really good, too, which I'll have to try to dig out -- I think Analog put it out.

[guscrown]

Sorry for my lack of details:

I design Televisions for a living, and the EMC part I am concerned with is Emissions (Radiate and Conducted). Immunity is done by someone else.

I do Hardware design, but in the most recent project I will also be in charge of Radiated and Conducted emissions compliance (FCC Section 15 Class B). In a previous project I work on (lets call it "Toogle TV"), I helped with EMC Compliance, but I was not the lead. The lead engineer had a very odd method of debugging, which to me seemed like luck.

Now I got the chance to lead this activity and get the certification, but I would like to do it using a more methodical way, and instead of adding patches, try and figure out some solutions board-wise.

[Neilm]

Sorry for my lack of details:

I design Televisions for a living, and the EMC part I am concerned with is Emissions (Radiate and Conducted). Immunity is done by someone else.

I do Hardware design, but in the most recent project I will also be in charge of Radiated and Conducted emissions compliance (FCC Section 15 Class B). In a previous project I work on (lets call it "Toogle TV"), I helped with EMC Compliance, but I was not the lead. The lead engineer had a very odd method of debugging, which to me seemed like luck.

Now I got the chance to lead this activity and get the certification, but I would like to do it using a more methodical way, and instead of adding patches, try and figure out some solutions board-wise.

A few points:

1) There isn't much differance between Emissions and Immunity - just the direction the signal goes. Good PCB layout techniques will reduce reduce
2) EMC compliance should be integral to the design - not tacked on afterward. At the start of the project or design certain "ground rules" should be decided on. These would include stratagies for the number of PCBs, the methodes of interconnection details on the PCBs for example number of layers, layer assignments, circuit positionson that PCB ect.
3) Experiance when testing for EMC problems is invaluable. It involves examining the circuits and trying to identify the signals that could be susceptable to or transmitting the noise, or even that internal EMI is a problem.

For example if you find that a unit is emmitting on a frequency that is a harmonic of a particular clock but you know that this has been turned off in the mode you are testing. An experianced EMC engineer might spot that the circuit design around that clock chip is susceptable to internal EMI and is being turned on during the test leading to the problem. A bit unlikely you might think but such  situation happened to me a few years ago.

I will suggest going and reading through the link I posted earlier - it contains several articals the will cover designing for EMC compliance in detail. Keith Armstrong has also produced a book on laying out a PCB for EMC compliance which I would recommend as invaluable for understanding EMC.

Yours

Neil