You should know that any filter you place in front of an LNA needs to
have a ridiculously low insertion loss in to not severely degrade the
noise figure if the LNA
It's likely that any switchable filter will have unacceptably high
insertion loss
A better approach is to use a first LNA with modest gain and good OIP3
and P1dB then your filters then another low noise stage
--
Principal Investigator
Shirleys Bay Radio
Astronomy Consortium
http://www.sbrac.org
On Jul 9, 2010, at 12:18 PM, Elvis Dowson <elvis.dow...@mac.com> wrote:
Hi,
On Jul 9, 2010, at 7:53 PM, Brian Padalino wrote:
You could try something like a switched filter bank as a preselector:
http://www.spectrummicrowave.com/sfb.asp
I was thinking of a discrete SMT type component, which I can mount
on a PCB board, those are really big.
That was something a quick google search found. Unfortunately, your
band-pass requirements are lacking. What types of channel bandwidths
do you want? How many channels? How much rejection are you looking
for?
I was initially thinking of a BPF in the 400Mhz to 4000Mhz range.
This would interface with a LNA of the same band-width. However, I
would like to be able to digitally control the BPF, to be able to
say filter frequencies, prior to sending it to the LNA, e.g. 1800Mhz
to 2200Mhz, and then switch back to 400 to 600Mhz, etc.
Doing a google search, I came across FPAA (Field Programmable Analog
Arrays), and I was wondering if using a switched bank of capacitors
and resistors, would do the trick?
I found one company http://www.anadigm.com/
haven't gone into the details of an FPAA, but was wondering if
someone else on this forum has looked into this type of thing before?
Could I potentially create my own externally switched capacitor &
resistor network, under control of a standard FPGA, to achieve the
same thing?
Best regards,
Elvis Dowson
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