Relationship between Resolution Bandwidth and Recived signal - RF
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Post subject: Relationship between Resolution Bandwidth
and Recived signal Posted: Mon Sep 25, 2006 4:04 am
Joined: Thu Jul 27, 2006 7:36 am
What is the relationship between Resolution Bandwidth
and Received signal strength.
Post subject: Posted: Mon Sep 25, 2006 1:25
Joined: Mon Jun 27, 2005 2:02 pm
There is no relationship as the
RSSI deals with amplitude and the Resolution BW deals with frequency
Post subject: Posted: Mon Sep 25, 2006 6:10 pm
Joined: Mon Sep 25, 2006 5:52 pm
As IR stated, there is not a direct relationship; but having a
large resolution bandwidth can make the noise power swamp a low level
Noise power in a 1hz bandwidth is -174dBm. Increase
your bandwidth, and your noise grows by 10*log(RBW).
So if your
resolution bandwidth is 10MHz, your noise power is
If your signal is smaller than this level, it will be unrecognizable.
(For different modulation formats, you also need to add more power
to demodulate, i.e. C/N)
To be able to "see" this signal, you
must decrease your bandwidth (as long as your signal can be processed
in the decreased bandwidth).
Posted: Tue Sep 26, 2006 4:14 pm
Mon Jun 27, 2005 2:02 pm
is true, but if you want to see the whole picture then you shouldn't
forget the tempearture contribution to the noise power:
K - Boltzmann's contasnt 1.38*10e-23 J/Kelvin
- Relative temperature in Kelvin
B - The bandwidth
terms, this formula becomes:
Pn=-174dBm+10 log (T/To) + 10 log
So any temperature above To (290 Kelvin degrees=17 deg C)
will also increase the noise power, and according to the explanation
given above will limit the strength of the received signal.
So in conclusion RSSI is not related just to the BW, but also to surrounding