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Measurement with PXA NFE

Question asked by jojo on Jan 19, 2013
Latest reply on Feb 2, 2013 by jojo

I have been looking at the PXA with NFE to measure very low noise like signal. My understanding is as follow:

- according to datasheet if I want to measure a signal of about -172dBm/Hz at 2GHz, connecting the signal directly to the PXA and without PreAmp nor NFE I will not be able to see this level but I will see about -153dBm/Hz. Using the PreAmp I gain about 10dB so I can read about -165dBm/Hz, and adding on top of that NFE I can reach -172dBm/Hz

- now if I use an LNA in my Rx path to raise the -172dBm/Hz signal to about -140dBm/Hz (thus well above the DANL of -153dBm/Hz) at PXA input I can make the measurement without the use of PreAmp and NFE.

Is this correct? Then I don't see what is the use of the NFE. I can just go down to the same level of measurement using an LNA?

Also what happens if I use the NFE after the LNA 30dB gain? Is the NFE going to reduce the level I read on the display by 10dB whatever the signal input power is or is it intelligent enough to understand that there is no contribution from the PXA?

Many Thanks for your reply