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BROAD BAND RF PCB DESIGN - RF Cafe Forums
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ashishbondia
Post subject: BROAD BAND RF PCB DESIGN Posted: Thu
Nov 20, 2008 8:41 am
Captain
Joined: Wed Aug 16,
2006 8:20 am
Posts: 23
Location: India
I am designing PCB
which should work from DC to 8 GHz. I am connecting 3 amplifiers in
cascade. Each of these broadband (DC to 8 GHz) amplifiers are 50 Ohm
matched internally. Only a DC blocking capacitor is needed at the input
and output. Here are some questions that are troubling me.
1.
What should be the minimum distance between the components (i mean the
amplifier stages). I am using lambada/4 as the minimum distance corresponding
to 8 GHz.
2. Should I use 2 capacitors (for DC blocking) between
any two amplifiers or a single Capacitor would be sufficient.
3. Will my design require some off chip impedance matching.
I am using Rogers Board material with 20 mil height, Er of 3.5 and
aCPWG traces.
Please share your valuable comments
regards-
Ashish
_________________
Ashish Bondia,
Design Engineer-
RF
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yendori
Post subject: Posted: Thu Nov
20, 2008 5:05 pm
General
Joined: Thu Sep 25, 2003
1:19 am
Posts: 50
Location: texarcana
Hello,
Quote:
1. What should be the minimum distance between the components (i mean
the amplifier stages). I am using lambada/4 as the minimum distance
corresponding to 8 GHz.
When I consider distance between
components I keep the distance as short as possible while keeping it
big enought for my soldering iron. Assuming the network is matched there
should not really be a max or min. The longer the trace, the more resistive
loss and possibilities for radiation, transmitted and received.
Quote:
2. Should I use 2 capacitors (for DC blocking) between
any two amplifiers or a single Capacitor would be sufficient.
As long as the Voltage rating and SRF work for your design,
you only need to use one cap.
Quote:
3. Will my design require
some off chip impedance matching.
If the gain blocks are
in fact 50ohms and you a the impedance of your line is 50ohms up to
8GHz then you should not need any matching. I would leave place holders
for some shunt elements just in case.
Good Luck
Rod
Posted
11/12/2012
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