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Q&A Filter Impedance Consideration

In a lot of textbooks, filters seem to be designed around a matching source and load impedance. However, If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(i...

2 answers  ·  posted 3y ago by jm567‭  ·  last activity 3y ago by Olin Lathrop‭

#2: Post edited by user avatar Olin Lathrop‭ · 2020-10-10T15:46:08Z (over 3 years ago)
Removed content-free fluff
  • Hello.
  • In a lot of textbooks, filters seem to be designed around a matching source and load impedance. However, If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(input to the LNA) to be large with respect to the source(antenna) in order to not attenuate the signal even further?
  • I guess another way to phrase this is why do we care about maximum power transfer at this stage and not preserving as much of the signal amplitude as possible instead?
  • In a lot of textbooks, filters seem to be designed around a matching source and load impedance. However, If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(input to the LNA) to be large with respect to the source(antenna) in order to not attenuate the signal even further?
  • I guess another way to phrase this is why do we care about maximum power transfer at this stage and not preserving as much of the signal amplitude as possible instead?
#1: Initial revision by user avatar jm567‭ · 2020-10-09T22:53:02Z (over 3 years ago)
Filter Impedance Consideration
Hello.

In a lot of textbooks, filters seem to be designed around a matching source and load impedance. However, If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(input to the LNA) to be large with respect to the source(antenna) in order to not attenuate the signal even further? 

I guess another way to phrase this is why do we care about maximum power transfer at this stage and not preserving as much of the signal amplitude as possible instead?