Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
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design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
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MSG and S21 - RF Cafe Forums
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but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: MSG and S21
Unread postPosted: Wed May
11, 2005 1:49 am
Tue Mar 15, 2005 11:43 pm
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?
Your advice is greatly appreciated.
postPosted: Wed May 11, 2005 2:48 am
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
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
Unread postPosted: Wed May 11, 2005 5:28 am
Joined: Tue Mar 15, 2005 11:43
Thanks for ur advice.
Yes, I think the matching network is not good.
designing for 5GHz , 2 -stages power amplifier.
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,
postPosted: Wed May 11, 2005 5:41 am
What is your operation bandwidth?
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?
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.