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Intermodulation for TETRA ETSI standard - RF Cafe Forums
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RDO-RF
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Post subject: Intermodulation for TETRA ETSI standard
Posted: Mon Mar 22, 2010 2:59 pm
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Captain |
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Joined: Wed Apr 08, 2009
7:53 am Posts: 17 |
Hello RF-Cafe folks!:
I have two questions
regarding the ETSI TS 101 789-1 V1.1.2 (ETSI standard
for TETRA Repeaters).
On point 5.5.2.3, we
the Limit Values for the intermodulation Attenuation.
Te text says: “The level of intermodulation product
shall be less than -60 dBc. In any case not requirement
greater than -36dBm shall apply”. I can’t quite
understand this phrase, so I have the following
two questions:
1) If I have a repeater of
2x32dBm output power. The maximum intermodulation
level needed to apply ETSI is -36dBm (-68dBc) or
-28dBm (32dBm-60dBc) ?
2) If I have a repeater
of 2x15dBm output power. The maximum intermodulation
level needed to apply ETSI is -36dBm (-51dBc) or
-45dBm (15dBm-60dBc) ?
Thank you!
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Jose Arrina |
Post subject: Re: Intermodulation for TETRA ETSI standard
Posted: Tue Mar 23, 2010 10:59 am
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Captain |
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Joined: Thu Mar 30, 2006
9:01 am Posts: 12 |
The spec means your intermods have to be at least
-60 dBc, and also cannot be any greater than -36
dBm in absolute power.
So your first example
would produce intermods at -28 dBm when down 60
dB from the +32 dBm. That is 8 dB too high.
In the second example the intermods are at -45
dBm when 60 dB down from the +15 dBm carriers, so
you're below the max absolute level of -36 dBm.
Example 1 fails, example 2 passes.
Hope
that helps.
Jose'
_________________ ... Jose' Arrina
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RDO-RF |
Post subject: Re: Intermodulation for TETRA ETSI standard
Posted: Tue Mar 23, 2010 1:21 pm
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Captain |
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Joined: Wed Apr 08, 2009
7:53 am Posts: 17 |
Hello Jose, thank you for your quick response.
Your add helps a lot, but I´m still not convinced
yet. If the standard was "Intermods have to be
at least -60 dBc, and also cannot be any greater
than -36 dBm in absolute power" it will be more
than clear. But it says: "...In any case
not requirement greater than -36dBm shall apply",
it doesn't clearly says that the absolute power
can´t be greater that -36dBm, it also can be understood
that they are not asking for requirement grater
that -36dBm... and the question will be: what is
a grater requirement? -37dBm or -35dBm???? I believe
that -37dBm is a grater requirement than -36dBm.
That is why I´m not convinced yet... on one
hand, I can understand what Jose said, but on the
other hand I can also understand that they ask for
-60dBc but that there is no need for a lower IMD
than -36dBm.
What can´t be greater than -36dBm,
the absolute IMD
tones or
the requirement?? I cant clearly understand
that from the standard...
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Posted 11/12/2012
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