Gain and Bandwidth - RF Cafe Forums
Post subject: Gain and bandwidth
Thu Apr 28, 2005 1:11 am
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 improve bandwidth."
Is there a formal derivation
to this statement? I'm curious why.
Thu Apr 28, 2005 1:25 am
Joined: Tue Mar 15, 2005 11:43 pm
I think it's related to this condition
"Gain-Bandwidth is equal to constant", which derived from Bode-Fano
Therefore, by designing for less than the maximum
obtainable gain, wider bandwidth will be obtained.
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?
people will design matching network to autocompensate the gain rolloff
and obtain a flat response, by sacrificing the VSWR.
Bode-Fano as a good starting point to sea if a matching is feasable.
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.