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Noise measurement with different spans and RBW

Question asked by Femtosecond on Aug 27, 2009
Latest reply on Aug 29, 2009 by GeorgeM
Hi,

I would like to measure the noise from DC - 10 MHz in the steps: DC - 10k, 10k - 100k, 100k - 1M, 1M - 10M

As the spans are different, the RBW is automatically adjusted and that is fine for me. After I measure all the curves I try to put them together to one whole trace from DC - 10 MHz. I'm measuring in units of dBm so I'm correcting each frequency range by -10*log(RBW) in order to add all of them together.

This however works only for some ranges as it's supposed to work. For instance, the ranges DC - 10k and 10k - 100k fit perfectly together. At the connection between 10k - 100k and 100k - 1M however there is a jump and I am not able to create a smooth curve.

I tried pretty much everything to get rid of theses steps but no success. Is there anything else that I have to take into account or that I have to hold on a fixed value to measure this and to put the traces together?

Thank you.  

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