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Wideband power amplifeir and input mismatch - RF Cafe Forums
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Jeanalmira
Post subject: Wideband power amplifeir and input mismatch
Posted: Sat Dec 23, 2006 1:59 am
General
Joined:
Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hello
All :
I have questions regarding wideband power amplifier design
(3-stages).
I have a case that the impedance of the device is low
in nature, therefore the the response is rather narrow and it is overly
sensitive to a little bit of changes.
I read somewhere that
to design wideband power amplifier with low impedance, there is a technique
called mismatch input matching?
I have tried this, and it is true
that when the input return loss is worse, the gain response is wider.
But I am not sure how to relate between wide gain response and
input mismatch? Or do I misinterpret this?
Please enlighten
me.
Thank you.
Wishing Merry Christmas and Happy Holiday
Regards,
Jean (Eudyna Devices Asia Singapore)
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IR
Post subject: Posted: Sat Jan 13, 2007 12:10 pm
Site Admin
Joined: Mon Jun 27, 2005 2:02 pm
Posts:
373
Location: Germany
Hello Jean,
If you consider wideband
response as flat gain curve then:
When you match an amplifier
to the best return loss then often you will get dips in the return loss
which will result in a non-flat gain response curve.
If you
will match the amplifier to a higher (bad) return loss than the gain
response will become flat and wideband.
From my experience:
I once matchd an amplifier for wideband operation (80MHz) and was able
to do so only by degrading the input return loss. The return loss still
had a reasonable value but less of what I could achieve for narrowband
operation.
I hope that I got to the point you meant, if you still
have questions please let me know.
_________________
Best
regards,
- IR
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fred47
Post subject:
MismatchPosted: Mon Jan 15, 2007 1:57 am
General
Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
Hi!
There
are theoretical limits to the bandwidth over which a close match can
be achieved in the presence of an irreducible reactance in the load
(which means "all real-world situations" !) You can see the books and
papers by Herbert Carlin, who did some of the ground-breaking work in
the area. (The most recent is "Wideband Circuit Design", the earlier
book is "Network Theory"). If they're available to you, there are helpful
discussions in the books "Feedback Maximization" by B.J. Lurie, "Network
Analysis & Feedback Amplifier Design" by H.W. Bode, and "Wideband
Matching" by Chen. These books are probably only available in university
libraries, with the exception of Lurie's book, which is published by
Artech House under their "In Print Forever" program.
These books
will probably tell you more than you really wanted to know about the
subject. <grin>
Good Luck!
Fred
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Jeanalmira
Post subject: Posted: Tue Jan 30, 2007 9:31 pm
General
Joined: Tue Mar 15, 2005 11:43 pm
Posts:
65
Location: Singapore
Thanks for the advice.
Posted 11/12/2012 |
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