Standing waves, doubts! - RF Cafe Forums

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Camelot
 Post subject: Standing waves, doubts!
Posted: Thu Jun 09, 2011 2:08 am 
 
Captain

Joined: Fri Jan 19, 2007 10:36 am
Posts: 7
Hello, I have some doubts about standing waves on antennas that hope you could clarify!
As far as I understood, in a transmission line where we want only carry power from a source to a load, we need to cancel the reflected wave by adapting the load with the impedance of the line. The result of this operation is S11=S22=0 and VWWR=1 that means no standing waves.
As far as I understood, in an antenna we want to also avoid standing waves by having VWWR=1 in order to avoid overloading problem to the power stage. From theory I know that the best radiating condition for an antenna is when it resonates that is when there is a standing wave… is that correct? How this condition is compatible with a VWWR=1 for a good antenna matching? Is there something that I’m not catching?

Regards,

Camelot
 
   
 
Kirt Blattenberger
 Post subject: Re: Standing waves, doubts!
Posted: Thu Jun 09, 2011 1:40 pm 
 
Site Admin
User avatar

Joined: Sun Aug 03, 2003 2:02 pm
Posts: 451
Location: Erie, PA
Greetings Camelot:

A 1:1 VSWR (infinite return loss) is definitely the preferred match condition on the transmission line. The standing wave you are thinking about is present on the antenna itself, not on the transmission line, and even then, a perfect standing wave is present only on a perfect antenna at specific frequencies.

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Posted  11/12/2012