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Absorption losses of different terrain types - RF Cafe Forums
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| Gavin
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Post subject: Absorption losses of different terrain types
Posted: Thu Feb 07, 2008 8:48 pm
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Joined: Thu Feb 07, 2008
8:46 pm Posts: 3 |
Hello, I am modelling an EDACS system operating
at 900MHz in Mentum Planet and would like to use
the clutter (map of various terrain types) file
for the area to improve the accuaracy of my coverage
plots. To do this I need to know the absorption
losses at 900MHz for various terrain type such as:
Fresh water Sea Water Forest
Dry ground Residential Dense Urban Core
urban (whatever that is) Industrial
Can anyone lead me towards some information on this?
Regards, Gavin Hill
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nubbage |
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Post subject:
Posted: Mon Feb 11, 2008 6:08 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 218 Location: London UK
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Hi Gavin I have contacted a few Planet users
to get some help on this one. Do you really mean
absorption by these media or do you mean the permittivity
and loss factor on reflection from their surfaces?
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Gavin |
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Post subject:
Posted: Mon Feb 11, 2008 8:13 pm
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Joined: Thu Feb 07, 2008
8:46 pm Posts: 3 |
Hi Nubbage, Thanks for looking into this,
as I understand it the 'clutter absorption loss'
is the loss resulting from absorption by foilage,
buildings, etc which is added to the path loss,
or vice versa subtracted from the signal strength.
So I think your description is probably more apt,
although the permittivity at 900MHz will have little
effect. In Planet (Ver 4.3) the setting
I am changing is in 'Propagation Model Properties'
under the 'Clutter Properties' tab where I select
'Edit CPA'. This brings up a table with
the various terrain types that I noted in my first
post. The variables that I am changing are under
the 'Clutter Absorption Loss (dB)' heading.
Regards, Gavin
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nubbage |
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Post subject:
Posted: Tue Feb 12, 2008 10:48 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 218 Location: London UK
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Hi Gavin I have received unhelpful feedback
on my enquiries into the settings for Planet. The
most helpful was "to consult the manual", the least
helpful was "to enquire at the British Museum" (the
group use the very latest software at a world-famous
Swedish system manufacturer). More helpfully,
I offer you a French graph of forest attenuation
which agrees well with another source I have. This
predicts 11dB/100m in winter (assuming deciduous
trees with no leaves) and 22dB/100m in summer with
wet leaves at 900MHz. There is also a polarization
dependence, but the above figures are for vertical
pol, normally used for mobile coms. I will up-load
my graph via image-shack as the clip board is ineffective
on this site. Although not strictly valid below
1000MHz, there are good design parameters for rolling
terrain and sea paths in the ITU Radio division
report ITU-R PN.530. Parameters for urban clutter
have been hotly debated for years and I am now not
so sure where the debate has led by today. More
next posting.
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nubbage |
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Post subject:
Posted: Tue Feb 12, 2008 11:04 am
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| General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 218 Location: London UK
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Gavin |
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Post subject:
Posted: Thu Feb 14, 2008 8:04 pm
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Joined: Thu Feb 07, 2008
8:46 pm Posts: 3 |
Hi Nubbage, Thanks for the feedback, I think
the graph will prove to be very helpful. As for
the Planet user who suggested "Use the manual",
I have, and there are no indications for absorption
losses at different frequencies. Regards,
Gavin
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Posted 11/12/2012 |
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