Also above 1 GHz directivity comes more and more into play (another reason
for hieght-scanning).
Bob Heller
3M EMC Laboratory, 76-1-01
St. Paul, MN 55107-1208
Tel: 651- 778-6336
Fax: 651-778-6252
=======================================================
"Luke Turnbull"
<luke.turnb...@trw.com To:
<wizbc...@charter.net>
> <emc-p...@ieee.org>
Sent by: cc:
owner-emc-pstc@majordo Subject: Re: High
Frequency Measurements
mo.ieee.org
02/13/2004 03:34 AM
Please respond to
"Luke Turnbull"
The reason for height-scanning is that there are unavoidable reflections
>from the groundplane, and the only way to ensure that your measurement
geometry is not causing a deep null is to scan the height. The reason that
reflections are unavoidable is that at 30MHz, absorber would have to be 2.5
m deep which is not practical or economic.k
At frequencies above 1 GHz, absorber is practical and economic, and I is
easy to put absorber on the ground to minimise the small effect that there
might be on your measurement due to ground reflections, and not bother with
height scanning.
Luke Turnbull
>>> "Wiz" <wizbc...@charter.net> 12/02/2004 15:36:41 >>>
Hello,
I have a need to make radiated measurements up to 40 GHz. I uses a low
loss cable that gives me enough dynamic range up to 18GHz. The cable is
very short and I have to move my measurements equipment out to the
antenna. I know I need to get a pre-amp and mixer, but what do I do
about the cable loss? I have called many places and I cannot find good
enough cable to measure to 40 GHz. The other alternative is waveguides
as I understand. Those would, I assume, be coupled directly to the
input of the mixer. This does not allow for antenna height adjustments
form 1 to 4m as required. I have seen other test reports where high
frequency data was taken where the antenna was held at about 1meter. I
can understand this since emissions will likely be very directional at
those frequencies. Is it acceptable to make measurements with the
receive antenna at 1 meter only?
Thanks for any information you can provide.
Wiz
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