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bless_fooling
Joined: 21 Feb 2008
Posts: 116
Helped: 2
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 22 Aug 2008 5:17 need help about RF power Amplifiers measure |
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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??
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disisku_22
Joined: 17 Jun 2008
Posts: 26
Helped: 2
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| 22 Aug 2008 8:17 Re: need help about RF power Amplifiers measure |
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| USE FIXED ATTENUATOR BEFORE FEEDING TO VNA
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GVVIN
Joined: 11 Apr 2008
Posts: 98
Helped: 15
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| 22 Aug 2008 9:33 Re: need help about RF power Amplifiers measure |
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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/news/224/AN-056_-_Output_Return_Loss_Of.pdf
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BigBoss
Joined: 17 Nov 2001
Posts: 928
Helped: 47
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| 22 Aug 2008 14:58 need help about RF power Amplifiers measure |
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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..
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xjbocx
Joined: 12 May 2005
Posts: 20
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| 22 Aug 2008 17:13 Re: need help about RF power Amplifiers measure |
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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.
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yashiro32
Joined: 05 Sep 2007
Posts: 24
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| 23 Aug 2008 17:25 Re: need help about RF power Amplifiers measure |
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| Can you explain what is the load-pull technique ?
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RFCMOS
Joined: 05 May 2005
Posts: 153
Helped: 20
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| 23 Aug 2008 20:16 Re: need help about RF power Amplifiers measure |
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Hi yashiro32,
check this link as short introduction:
http://www.microwaves101.com/encyclopedia/loadpull.cfm
Hope this helps.
RFCMOS.
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