Design Con 2015
Breaking News
News & Analysis

Questions On EMC Pre-Compliance Testing for Radiated Emissions

7/31/2013 09:00 AM EDT
5 comments
NO RATINGS
More Related Links
View Comments: Newest First | Oldest First | Threaded View
JanineLove
User Rank
Blogger
IEEE EMC2013
JanineLove   8/5/2013 3:25:35 PM
NO RATINGS
Ken's in Denver this week for EMC. Ken, be sure to let us know how it goes.

Kenneth Wyatt
User Rank
Blogger
Re: EMC Questions
Kenneth Wyatt   8/4/2013 10:46:32 AM
NO RATINGS
Hi Sanjib.A, you pose several questions and I'll answer the best I can. As I'm not completely familiar with GTEMs, except from what I've read, you may need to consult other experts in the field.

I believe there is a "best" lower limit with GTEMS, depending on their size. So assuming the product you're testing does not exceed the size recommendation and the frequencies in question are - say - above 150 MHz, I've read they can be accurate enough for pre-compliance testing. Please correct me if I'm wrong...

As for your second question, there are "sources" of RF energy, such as devices producing fast edges (oscillators, buffers, ASICs, A/D, D/A, etc.) and these sources can couple via conductive, radiative, inductive or capacitive means to "radiating structures", such as cables, enclosure seams, etc.

Typically, it is common-mode currents that radiate via these radiating structures. As long as the loop area between the differential mode source and return currents is small, then DM emissions is usually a second-order effect.

A horizontal emission might come from a horizontal cable or a vertical seam, and visa versa with vertical emissions. You can also have a combination of the two.

Kenneth Wyatt
User Rank
Blogger
Re: Detailed
Kenneth Wyatt   8/4/2013 10:37:00 AM
NO RATINGS
Thanks elctrnx_lyf. You might also check The EMC Blog at: http://www.edn.com/electronics-blogs/4376432/The-EMC-Blog for additional Q&A following my webinar.

Sanjib.A
User Rank
CEO
EMC Questions
Sanjib.A   8/4/2013 2:45:16 AM
NO RATINGS
Hello,

I missed the webinar, but thanks for sharing the link and Q&A. I have the following questions for which I have not got satisfactory answers:

1. Is it okay to use a GTEM cell to do the pre-compliance testing? I saw a big difference in the results when we tried to fix a power supply issue in GTEM cell vs when we tried the same fix in an anechoic chamber. Would you suggest avoiding GTEM cell for pre-compliance testing?

2. How to interpret about the source of the noise (PCB or Cable; Common-mode or diff mode) if a frequency component is appears in Horizontal scan but not in the vertical scan or vice-versa or appears in both?

Best Regards, 

elctrnx_lyf
User Rank
Manager
Detailed
elctrnx_lyf   7/31/2013 1:19:56 PM
NO RATINGS
These extensive details are definitely helpful to understand the basic of Emc precompliance testing.

Radio
LATEST ARCHIVED BROADCAST
EE Times Senior Technical Editor Martin Rowe will interview EMC engineer Kenneth Wyatt.
Top Comments of the Week
Like Us on Facebook

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
EE Times on Twitter
EE Times Twitter Feed
Flash Poll