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IMD asymmetry

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Leiser

Leiser

Automotive
Joined
Apr 19, 2007
Messages
92
Location
ES
Hello,

I am measuring IMR3 of a DAB band III LNA from production. Some boards show IMR3 asymmetry and others not. Does anyone know what could be the cause? The LNA is implemented by a MIMIC MGA-62563.

Also the IMR3 has drop for the case of asymmetry.

I attach the two plots.

 
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One old trick is to add some attenuation (e.g. -6dB) between the UUT and the measuring instrument (the spectrum analyzer side, *not* the signal generator side). This can help to ensure that the line is 'flat', and confirm that your measured ratios are stable (real measurements, not artifacts).


 
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Thanks very much for you prompt answer.

I tried but didn't work. It seems some ESD protection diodes from different batches are responsible for the IMR asymmetry. I changed them and it work.

 
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Excellent. Congratulations on figuring it out so fast.
 
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