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Amplitude Match - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

 Post subject: Amplitude Match
Posted: Tue Oct 17, 2006 8:49 am 

Joined: Fri Sep 29, 2006 11:05 am
Posts: 4
Ok guys, here's another one....

I've been asked to perform a "Amplitude Match" between frequencies on a batch of 4 coax cable assemblies.

What is Amplitude Matching ? How would you perform this on a VNA ? :oops:

 Post subject: Amplitude Match
Posted: Tue Oct 17, 2006 10:43 am 
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 268
Location: London UK
I guess it depends to some extent on what is implied by "assemblies". These could be quite complex, or just individual lengths with a connector each end.

In the latter case, different cable types will have different dispersion characteristics of the loss vs frequency response.

If you set up a VNA to display S21 across the range of frequencies asked for, there you have it: compare the curves.

If you have a complex assembly with for example power splitters, you would have to compare port A on one with port A for the others, and go on doing this for the other ports, with all other ports correctly terminated.

 Post subject:
osted: Tue Oct 17, 2006 10:56 am 

Joined: Fri Sep 29, 2006 11:05 am
Posts: 4
Thanks for the reply !

This is a simple coax assembly with 1 connector on each side.

So I'm looking at a S21 measurement. Take the first one, measure it and save it to memory and compare the rest vs. that first one. The difference would be the amplitude difference with the first being the baseline.

Format would be Logmag ?

So it looks like I'm looking at an insertion loss difference between cables at a given frequency span ?



 Post subject:
Posted: Tue Oct 17, 2006 1:28 pm 
Site Admin
User avatar

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 406
Location: Germany

Yes the format should be Log Mag.
You should measure the S21 for each cable in the given frequency range and compare the obtained S21 curve vs. the frequency.

Best regards,

- IR

Posted  11/12/2012

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