FreeLists / si-list / [SI-LIST] Re: ESD solution on antenna output (re-send)

["Steve Rogers" <SRogers@xxxxxxxxxxxxx>]

Your getting lots of good info now and as suggested you need to do some =
testing. However, as this ESD problem isn't cooking anything, as a last =
resort you might be able to work around it if you can add in a periodic =
reset? I believe a number of specifications allow you to pass if the =
equipment recovers after the ESD has been removed? Have a look at your =
spec and see what you actually need to do.=20

Steve Rogers B.Eng (Hons) C.Eng IEE
RF Design Engineer

Micromill Electronics Limited
Leydene House
Waterberry Drive=20
Waterlooville Hampshire
PO7 7XX

Tel: +44 (0) 23 9236 6600
Fax: +44 (0) 23 9236 6673

Registered No. 1456922 (England). =20
Registered Office Brook Road
Wimborne, Dorset BH21 2BJ

***********************************************************************

"This email and any attached files are confidential  and may be legally =
privileged.If you are not the addressee, any disclosure, =
reproduction,copying, distribution,, or other dissemination or use of =
this communication is strictly prohibited. If you have received this =
transmission in error please notify the sender immediately and then =
delete this email.

It is the policy of Micromill Electronics Limited that no legally =
binding statements, representations or commitments (collectively =
'statements') may be made by email. Any such statements must be =
confirmed either by facsimilie or by post before they will have legal =
effect. The sender of this email is not authorised to commit the company =
in any way and the addressee is hereby formally notified of that fact."

***********************************************************************





-----Original Message-----
From: Ian Barrett [mailto:Ibarrett@xxxxxxxxxxxxxx]
Sent: Wednesday, February 04, 2004 6:34 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: ESD solution on antenna output (re-send)


OK update. Thanks again for all the replies, it has certainly helped to
clarify things in my mind.

The device is a 400MHz transmitter that fits in the palm of your hand, =
and
the failure mechanism in nothing to do with the output stage - another =
part
of the circuit is going into a lock-up that requires a power cycle to =
reset.
Parallel work is looking at exactly how and why this is happening, but I =
am
looking at how the ESD is coupling into the circuit in the first place.

I have tried the experiment below - short the antenna to ground - and =
the
circuit locks-up. When I completely isolate the antenna (from the output
stage and any surrounding ground plane) it survives. Unfortunately,
insulating the antenna as someone suggested, is not an option.

Ian.



----- Original Message -----
From: "Ingraham, Andrew" <a.ingraham@xxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, February 03, 2004 08:57 AM
Subject: Re: [SI-LIST] ESD solution on antenna output

What would happen if you (experimentally) replace the inductor with a =
short;
i.e., directly short the antenna to ground?  Of course it wouldn't =
transmit
or receive, but it might help prove/disprove your hypothesis that the
failure mechanism involves the ESD getting into the ground system and =
then
doing some damage there.

If it is what you suspect, then we need to get into a different =
mindframe.
Most of the replies have assumed that the ESD problem is a voltage =
between
the signal and ground terminals, across the amp input or output.  But if
it's a spike event IN the ground system, then you have to figure out =
where
it goes within your ground system and how it causes the damage.  Maybe =
the
problem is that the inductor is connected to the wrong "ground" point!

An inductor to ground is used on many antenna terminals, but apparently =
not
everywhere.  I think they are fairly common on HF/VHF/UHF antennas that =
are
not already self-grounding by having some sort of loop.  (A base-fed
vertical antenna is not self-grounding, but a shunt-fed one is.)  If the
antenna to electronics are capacitively coupled, a mobile or outdoor
antenna could build up several thousand volts of static charge from wind
and/or rain hitting it, and then you can have something like a blown
capacitor and electronics.  Hence the inductor.  It provides a DC and =
low
frequency current path to ground to bleed off this static build-up, as =
Ray
Anderson mentions.

But this assumes 2-terminal (1-port) thinking; i.e., that the enemy is
voltage ACROSS the terminals, not something within the electronics' =
ground
system.

If you think inductive kick might be worsening the problem, a =
few-hundred
ohm resistor might be better.

Another variation is to use transformer coupling to the antenna, which =
if
narrowband might reject more out-of-band energy while shunting low =
frequency
ESD energy to ground.

But, if you are fairly sure the problem is the ESD getting into your =
ground
plane and then causing damage, you need to think of different solutions.

Regards,
Andy


------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20


________________________________________________________________________
This email has been scanned for all viruses by the MessageLabs Email
Security System. For more information on a proactive email security
service working around the clock, around the globe, visit
http://www.messagelabs.com
________________________________________________________________________
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu