EMI suppression at 2.4 GHz
EMI suppression at 2.4 GHz
(OP)
I can find chokes (Fair-rite 61 material) that are good to 1000 MHz. What materials are good for attenuating frequencies above a GHz? I have a legacy amplifier in a system that we want to get a CE mark on. It is having immunity issues in the band from 100 MHz to 2400 MHz. I have seen good initial test results by adding chokes with 43 material (<250 MHz) on the amplifier pins, so I'm hoping to solve this by blocking the EMI path across the full band. The EMI source is predefined, and I'd rather not redesign the EMI receptor (amplifier).
Thanks,
Z
Thanks,
Z





RE: EMI suppression at 2.4 GHz
Attenuates higher frequencies, but not as convenient as a ferrite coil.
To get good attenuation, you need current on the wire to be surrounded by Magram, then metal.
Picture coax., your problem wire is the center conductor, Magram is the Teflon, and metal on the outside. Most Magram is very flexible, you can make a loop.
RE: EMI suppression at 2.4 GHz
RE: EMI suppression at 2.4 GHz
RE: EMI suppression at 2.4 GHz
http://www.arc-tech.com/cables.php
www.MaguffinMicrowave.com
Maguffin Microwave wireless design consulting
RE: EMI suppression at 2.4 GHz
So far I've found I can get about a 6-12 dB improvement at 2.4 GHz with 61-material chokes on my power and output leads of my amplifier.
I ran a few calculations and it looks like I'm only getting 12-14 dB of shielding off my enclosure so I may have better luck with improvements there. I'm starting to evaluate feedthrough caps at the entry into the main enclosure. Tusonix has some that are good to 10 GHz.
Z
RE: EMI suppression at 2.4 GHz
If you don't want to wait for the magram, try the cheap approach with salt water.
RE: EMI suppression at 2.4 GHz
RE: EMI suppression at 2.4 GHz
NASA has a really good article online about shielding effectiveness - NASA Contractor report 4784 - Design Guidelines for Shielding Effectiveness, Current Carrying Capability, and the Enhancement of Conductivity of Composite Materials. It is available here:
www.twpinc.com/pdf/19970036055_1997067804.pdf
Z