[SI-LIST] Re: Emission Problem with Ethernet
- From: Hany Fahmy <hfahmy@xxxxxxxxxx>
- To: "'deepaksiengg@xxxxxxxxx'" <deepaksiengg@xxxxxxxxx>, "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Sat, 18 Sep 2010 05:34:14 -0700
Try to use shielded RJ45, u may get lower emission.
----- Original Message -----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx>
To: si-list@xxxxxxxxxxxxx <si-list@xxxxxxxxxxxxx>
Sent: Wed Sep 15 00:51:47 2010
Subject: [SI-LIST] Emission Problem with Ethernet
Hello Experts,
I am working on improvement of Ethernet port.
In design, we are getting a high emission at 125MHz of 53 dbuV(case:Ethernet
communication via unshielded LAN-cable).
I would like to reduce this db level below 40db.
Circuit description:
1.RJ45 connector with inbuilt magnetic(with CM coil)
2.ESD protection on all four signals.
3.RJ45 connector is place on the corner of the PCB in cavity of C shape. i.e
connector in not place on top of PCB, but solder in C shape cavity.
4. to reduce the emission, an external CM choke is used. which is not
passing the signals(becasuse of Differential Signal level= 0.4Vp-p). so I
shorted the footprint with links.
5. On RJ45, system is only using signal ground(no chassis ground).
Restriction of the design:
1. can not use the chasis ground, due to placement problems.
2. can use only unshielded cable
Could you please suggest some other possible way to handle this situation.
I'm stressing on Chassis ground..
Thanks,
Deepak
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