Post subject: Gain and bandwidth
Unread postPosted: Thu
Apr 28, 2005 1:11 am
Joined: Sat Apr 23,
2005 2:09 pm
Location: Tampa, FL
I was just reading the Pozar book and on p.553 it mentions that "it
is preferable to design for less than the maximum obtainable gain to
Is there a formal derivation to this statement?
I'm curious why.
Unread postPosted: Thu Apr 28, 2005 1:25 am
Joined: Tue Mar 15, 2005 11:43
I think it's related
to this condition "Gain-Bandwidth is equal to constant", which derived
from Bode-Fano Theorem.
Therefore, by designing for less than
the maximum obtainable gain, wider bandwidth will be obtained.
Thanks and Regards,
Unread postPosted: Mon May 02, 2005 1:30 pm
The last post is absolutly correct. Fanos limit shows that for wider
bandwidth, the gain will be reduced.
Unread postPosted: Tue May 03, 2005 8:49 am
Aint Bode-Fano's criterion showing the VSWR-bandwidth product that
a matching network can have for a given quality factor mostly for passive
devices shuch as antenas?
I always had the impession that remplacing
VSWR by GAIN was an oversimplification. In my mind it only work as stated
if the device in unilateral.
Second, what is this GAIN-Bandwitdh
tradeoff? What gain? A flat gain or the Maximum available gain over
frequency, whatever value or rolloff it shows?
Very often people
will design matching network to autocompensate the gain rolloff and
obtain a flat response, by sacrificing the VSWR.
I see Bode-Fano
as a good starting point to sea if a matching is feasable.
Unread postPosted: Tue
May 03, 2005 11:43 am
You are correct , it is a criterion for
passive networks. The matching networks are passive, therfore, the wider
the bandwidth the higher the loss, hence lower gain.