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LNA and filters - RF Cafe Forums
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veerasamy
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Post subject: LNA and filters
Posted: Mon Oct 12, 2009 12:41 am
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Joined: Wed Oct 07, 2009
6:27 am Posts: 6 |
In the receiver chain which should come first? LNA
or BPF. In most of the schematics, I see BPF coming
first. I have a wide band LNA. Can i use it at the
beginning of the filter chain(because I need high
sensitivity)? What will be the problems in this?
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Alberto |
Post subject: Re: LNA and filters
Posted: Mon Oct 12, 2009 4:29 am
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Joined: Sun Oct 04, 2009
5:17 pm Posts: 6 |
Hi veerasamy, The BPF is usually placed before
the LNA stage to protect it from out-of-band interference.
In this case the total noise figure is increased
by a quantity equal to the insertion loss of the
filter itself. Strong out-of-band interferer
can generate high intermodulation products depending
from the IP3 of your LNA. Very strong interferer
can also cause distortion, if they are close or
higher than P1dB.
Regards, Alberto
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abhityagi85 |
Post subject: Re: LNA and filters
Posted: Thu Jan 14, 2010 3:01 am
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Joined: Thu Jan 14, 2010
2:57 am Posts: 4 |
Hi veera,
Mostly you will not be using a
bpf if your antenna is narrowband and you use
an impedance matching circuit. But the rejection
of unwanted signals is always important consideration
before an LNA for good performance otherwise more
power will appear @ input of lna which will
affect its linearity!!!
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ghazaleh |
Post subject: Re: LNA and filters
Posted: Tue Jul 13, 2010 9:36 am
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Joined: Tue Jul 13, 2010
8:57 am Posts: 1 |
hello we want to design a receiver in 2.4Ghz
with advanced design system software,& we don't
know how to find the moduls of LNA & mixer &
band pass filter & LPF & amplifier &
oscillator &... help us please..
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abhityagi85 |
Post subject: Re: LNA and filters
Posted: Tue Jul 13, 2010 3:13 pm
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Joined: Thu Jan 14, 2010
2:57 am Posts: 4 |
I have used models of various components while designing
the wideband frontend for SDR.
I remember
that the Avago technologies provides the model for
their LNA. Johansons dielectric also provides
models for their passives.
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Posted 11/12/2012
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