[SI-LIST] Re: Slot Antenna
- From: "EVANS,JEFF (HP-Cupertino,ex3)" <jeff_evans@xxxxxx>
- To: 'Ibrahim Khan' <ikhan@xxxxxxxxxxxxxxxxxxx>
- Date: Mon, 29 Jul 2002 17:00:46 -0400
Irahim,
The comment about the decoupling sprinkled around was really to short out
the patch antenna.
To detune the efficiency of the slot antenna without the underlying closely
coupled ground plane, you need to think about the driving source. If the
source is TEM propagation from within your PCA, you are probably better off
adding the ground plane (this is why many EMC advocates prefer solid outer
ground planes, limited surface structures such as long traces or large
patches, and some form of board edge treatment such as reflective ground
stitching or lossy RC circuits acting somewhat as "shock absorbers").
If you are concerned about the slot radiating from the two patches as the
driving source, then short out the slot antenna structure with a capacitor
or two across the slot (between 3.3 and 1.5). If you are concerned about
noise coupling between the two voltage rails then make these RC circuits to
dissipate the energy. If your slot antenna is radiating above 1 GHz you may
need to use the ground plane approach anyway since it may be difficult to
implement a low impedance component pad topology that will work effectively
across the gap. If it is below that frequency, I would recommend spacing
them about lambda/20 apart and using a capacitor value with a low impedance
for that frequency range.
Cheers!
-Jeff Evans
EMC Architect/Lead
Research and Development
Industry Standard Server Division
Hewlett Packard Company
-----Original Message-----
From: Ibrahim Khan [mailto:ikhan@xxxxxxxxxxxxxxxxxxx]
Sent: Saturday, July 27, 2002 8:29 AM
To: EVANS,JEFF (HP-Cupertino,ex3)
Cc: si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Slot Antenna
Jeff,
Thanks for your input. I do not have nay signals crossing the split. The
nearest ground is 2 signal layers away. My concern is that these voltage
islands sitting side by side may form a slot antenna and radiate. Questions
are: 1. How far apart these voltage islands should be from each other. 2.
If decoupling capacitors along the two adjacent edges can help then how far
apart should the caps ber placed along the edge.
Thanks,
Ibrahim Khan
-----Original Message-----
From: EVANS,JEFF (HP-Cupertino,ex3) [mailto:jeff_evans@xxxxxx]
Sent: Friday, July 26, 2002 6:34 PM
To: Ibrahim Khan; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Slot Antenna
Ibrahim,
Besides the slot antenna which might be exacerbated by signals crossing the
split, or EM noise propagating from inside your PCA, it sounds like you now
also have two patch antennas (3.3 and 1.5). Actually, both of these effects
can be mostly mitigated with an underlying continuous closely coupled ground
plane (2 to 4 mils) and good high frequency discrete decoupling capacitors
sprinkled around both voltage planes.
-Jeff Evans
-----Original Message-----
From: Ibrahim Khan [mailto:ikhan@xxxxxxxxxxxxxxxxxxx]
Sent: Friday, July 26, 2002 8:59 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST]
Hello SI Gurus,
If we have a split plane with two different voltages on the splits (e.g 3.3
on one side and 1.5 on the other). Will it make a slot antenna.
Thanks for any insight.
Ibrahim Khan
------------------------------------------------------------------
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:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//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
------------------------------------------------------------------
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:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//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
Other related posts:
