AM-PM modelling - RF Cafe Forums

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ben00i
 Post subject: AM-PM modelling
Posted: Wed Mar 21, 2007 7:42 am 
 
Lieutenant
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Joined: Wed Mar 21, 2007 7:08 am

Posts: 4

Hi,

Has anyone ever worked on AM-AM and AM-PM modelling? If you refer to the following paper by Saleh, 'Frequency-Independent and Frequency-Dependent Nonlinear Models of TWT Amplifiers', IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-29, NO. 11, NOVEMBER 1981, the am-am and am-pm models presented all start from 0. However, my measurements of both am-am and am-pm does not start from zero. Do I need to normalize my result? In that case, how do I normalized my AM-PM result? It seems weird when the y-axis is in terms of phase and the x-axis is in terms of power. Thanks. Love the help u all provide!
 
   
 
IR
 Post subject:
Posted: Thu May 17, 2007 4:14 pm 
 
Site Admin
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Joined: Mon Jun 27, 2005 2:02 pm

Posts: 406

Location: Germany

If I understand your problem correctly:

AM-PM and AM-AM are for providing relative data and not absolute data. That means that you should not focus on the absolute values which you get but on the phase and amplitude differences as a function of the input power variation. From this you can draw out useful data about the compression charactersitics of the PA and be able to characterize the distortion for designing pre-distortion or other solutions.

Posted  11/12/2012