To: <Ibarrett@xxxxxxxxxxxxxx>, <davidjp@xxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>, <Pommerenke@xxxxxxxxxxx>
Date: Mon, 2 Feb 2004 16:46:19 -0700
Ian,
Perhaps your colleague was thinking in terms of audio where an inductor to
ground is common practice. It's been a while since I've done RF, but the
key to passing ESD was to have a low inductance path (high surface area)
between the antenna and the EUT chassis. I would suggest no inductor to
ground, since precursor events are in the 100 pS range (~ 3.5 GHz equivalent
frequency), and inductance is your enemy. Sometimes small valued capacitors
were additionally required to shunt the current. Insulated(rubber
coated)antennas work well since they offer some protection from user abuse,
and change your test from direct contact to air discharge. High energy,
fast shunting diodes are readily available and will probably be required on
any supply.
Ken
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ian Barrett
Sent: Monday, February 02, 2004 11:41 AM
To: 'davidjp@xxxxxxxxxxx'; si-list@xxxxxxxxxxxxx;
'Pommerenke@xxxxxxxxxxx'
Subject: [SI-LIST] ESD solution on antenna output
I am currently having a lively discussion with a colleague about an ESD
problem we have encountered. The trouble is I don't think either of us know
enough to be able to convince the other of our point of view.
The product is a small radio transmitter that is very susceptible to an ESD
spike applied directly to it's antenna. The design includes a small inductor
between the antenna output and ground. My colleague (the designer) put it
there to try and alleviate any potential ESD problems. I have found that I
cannot solve the ESD susceptibility problem without removing it.
He claims 'any ESD experts will tell you to place this inductor' and wants
me to try and find another solution to the problem. But I think the inductor
is making the situation worse by coupling the ESD spike onto the ground
plane.
Can anyone offer some theory to back up either argument?
Ian.
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