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MSG and S21 - RF Cafe Forums
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Jeanalmira
Post subject: MSG and S21
Unread postPosted: Wed May
11, 2005 1:49 am
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Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi
All :
I have one problem regarding MSG and S21. Currently I simulate
small signal performance of power amplifier.
I observed that MSG
is around 14.6dB, however |S21| is only 4.1dB.
I understand that
MSG= |S21| / |S12|
the |S21| is 1.6018
while |S12| is 0.1097.
My doubt is, why in this case the |S21| is much smaller than MSG?
besides |S12|, are there any other factors that affect?
Thank
you.
Your advice is greatly appreciated.
Best Regards,
Jean
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Guest
Post subject:
Unread
postPosted: Wed May 11, 2005 2:48 am
Hello Jean,
Your
calculation is not correct.
The MSG ratio you obtained is not in
dB units. You should multiply this ratio - 14.6 by 10*log >>>>>10*log
14.6=~11.65dB
You should check why your S21 is so small? I assume
that this can be caused by poor matching or wrong bias operation point.
If you can tell more details about your circuit, I might be able to
help you.
Good luck!!!
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Jeanalmira
Post subject:
Unread postPosted: Wed May 11, 2005 5:28 am
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Joined: Tue Mar 15, 2005 11:43
pm
Posts: 65
Location: Singapore
Thanks for ur advice.
Yes, I think the matching network is not good.
I'm currently
designing for 5GHz , 2 -stages power amplifier.
This problem
of low gain (S21) is on my second stage.
This is my first-time designing
on 5GHz range.
Any design tips? :idea:
Because I observe that
it's very hard to have "gain-matching" network at this frequency range.
any advice is greatly appreciated. :wink:
Thanks and Regards,
Jean
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Guest
Post subject:
Unread
postPosted: Wed May 11, 2005 5:41 am
Hello Jean,
You
are welcome.
What is your operation bandwidth?
The matching
netwroks done in this freqency range are consisted of transmission lines.
They can be broadband or narrowband.
Which substrate are you
using? What is the device that you use in your final stage?
S21=4dB
for a device, which is capable for a gain of at least 5dB more shows
about very poor match. If you can provide more details about the questions
above it will help.
Posted
11/12/2012
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