Thread: how to test the S11, S12, S21, S22 of my LNA demo board


Permlink Replies: 2 - Pages: 1 - Last Post: May 21, 2012 1:09 PM Last Post By: zubair_rafiq Threads: [ Previous | Next ]
robismyname

Posts: 5
Registered: 05/20/12
how to test the S11, S12, S21, S22 of my LNA demo board
Posted: May 20, 2012 8:22 AM
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I received a RFMD LNA (rf2472g) board. I would like to test the S parameters.

I dont know for sure how to connect the my INPUT and OUTPUT of the LNA to my VNA Port 1 and Port 2.

I want to be sure before i do this because I dont want to damage/ruin the board.

Do i just connect VNA port 1 to LNA input and VNA port 2 to LNA output?

Would I ever need to connect the VNA port 2 to the LNA input?

Would I ever need to connect the VNA port 1 to the LNA output?
Dr_joel


Posts: 2,667
Registered: 12/01/05
Re: how to test the S11, S12, S21, S22 of my LNA demo board
Posted: May 21, 2012 12:22 PM   in response to: robismyname in response to: robismyname
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robismyname wrote:
I received a RFMD LNA (rf2472g) board. I would like to test the S parameters.

I dont know for sure how to connect the my INPUT and OUTPUT of the LNA to my VNA Port 1 and Port 2.

I want to be sure before i do this because I dont want to damage/ruin the board.

Do i just connect VNA port 1 to LNA input and VNA port 2 to LNA output?

Yup

Would I ever need to connect the VNA port 2 to the LNA input?
not normally

Would I ever need to connect the VNA port 1 to the LNA output?
only if you did the step above.
zubair_rafiq


Posts: 9
Registered: 05/29/09
Re: how to test the S11, S12, S21, S22 of my LNA demo board
Posted: May 21, 2012 1:09 PM   in response to: robismyname in response to: robismyname
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Attachment 2472GDS.pdf (217.8 KB)
Agilent’s Expert can explain this much better however, I believe that following may be useful after reading datasheet of your LNA.
1. Calibrate your system (10MHz to 6GHz depending upon your VNA).
2. Connecting of both ports and then taking All S parameters your board will be safe. Other wise terminate remaining port while taking S11 or S22.
3. In your case minimum P1dB is -12dBm so set your power level below -12dBm- 14dB( Max Gain) = -26dBm.
4. You can also take power sweep this will calculate compression Points (depending upon VNA options).
5. For Power Sweep( if desired). Power sweep is good for checking LNA at its extreme but never set power more than damage level of your device. Depending upon your VNA’s maximum input level at port2 you can decide weather you need additional attenuators at output port. It would be better if you connect 10-20db attenuator and then adding magnitude offset same as the value of your attenuator. . In your case may be -87dBm to 0dBm in different steps e.g. -87to -67dBm and so on.

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