need help about RF power Amplifiers measure

anybody can give me some idea about the RF power Amplifiers measurement
such as S22,S21..., For most of the RF power Amplifiers 's output power is too large and if we use vna, it maybe damage to the tester

anybody also can give me some idea about the WLAN RF matching skill? or some paper about the wlan matching?

USE FIXED ATTENUATOR BEFORE FEEDING TO VNA

I don"t think so. An attenuator placed will affect the reflected power also. Usually S22 of high power Amplifiers are not measured or you have to go for Hot S22 measurements.

http://www.sirenza.com/documents/new...rn_Loss_Of.pdf

S-Parameters are valid ONLY small signal operating conditions.While the output voltage and currents are high swinging you can NOT measure s-parameters because they are changed by OP..
Instead, you should use load-pull technique to find correct output and input impedances by using adjustable tuner and observing reflected and incident waves at both ports..

I agree with BigBoss
VNA is used for small signal parameters
for PA, you should use the LOAD PULL.
you change the load of the PA, then measure the gain and ACPR.

Can you explain what is the load-pull technique ?

Hi yashiro32,

check this link as short introduction:

http://www.microwaves101.com/encyclopedia/loadpull.cfm

Hope this helps.

RFCMOS.