Gain and bandwidth - RF Cafe Forums
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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 improve bandwidth."
Is there a formal derivation to this statement? I'm curious why.
Unread postPosted: Thu Apr 28, 2005
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 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?
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.
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