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Selectivity & adjacent parameters - RF Cafe Forums
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| evgkru
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Post subject: Selectivity & adjacent parameters
Posted: Wed Dec 16, 2009 8:37 am
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Joined: Wed Dec 16, 2009
8:28 am
Posts: 2 |
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Hi guys,
I have a question about Selectivity &
adjacent paremeters.
What is deference between
receiver selectivity and adjacent parameters?
Glad for any help.
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SunshineDesign |
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Post subject: Re: Selectivity & adjacent parameters
Posted: Fri Dec 18, 2009 11:54 am
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Joined: Sat Nov 08, 2008
11:35 pm
Posts: 30
Location: Ramona, CA
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evgkru - can you be more specific as to what exactly
you are asking. I presume filter/band selectivity
of the receiver and adjacent channel power?
Receiver selectivity is the ability to receive
the desired signal without inteference from other
adjacent signals and the filter selectivity and
sensitivity (i.e. noise figure and gain) of the
receiver play a part in this as does the receivers
ability to not be sensitive to the adjactent channel
effecting the receiver gain of the desired signal
(desense as this effect is called).
The
Adjacent Channel power is the integrated band power
of any signals adjacent to the desired channel being
received.
_________________
Sunshine Design Engineering
Services
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evgkru |
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Post subject: Re: Selectivity & adjacent parameters
Posted: Sun Dec 20, 2009 6:54 am
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Joined: Wed Dec 16, 2009
8:28 am
Posts: 2 |
Hi, Thank you for your reply. I am looking
for receiver with 60dB selectivity @±50KHz On
one of the data sheets
http://www.radiometrix.com/node/343 I see only
Adjacent channel parameter (Adjacent Channel: -70dBm)
Can I refer to this parameter as selectivity?
happy Xmas
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SunshineDesign |
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Post subject: Re: Selectivity & adjacent parameters
Posted: Mon Dec 21, 2009 10:47 pm
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Joined: Sat Nov 08, 2008
11:35 pm
Posts: 30
Location: Ramona, CA
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The two are related but not equal. Adjacent Channel
Power or Rejection is a band integrated power measurement.
Selectivity is a point to point power comparison
to some set /RBW or /Hz. You would define the primary
band and the adjacent band and then compare min,
max, average and/or defined frequency points. For
instance, a filter I worked on had a passband min
to a band trap adjacent in upper sideband. I had
to have so many dBc rejection or selectivity. On
the other hand for CDMA I might have +15dBm/CDMA
Band power compared to -32dBm/CMDA Adjacent channel
power in the upper channel for a 47dB Adjacent Channel
Rejection. So you could estimate but not equate
from the info you have. You would have to test.
_________________
Sunshine Design Engineering
Services
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Posted 11/12/2012
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