AnsweredAssumed Answered

N9030A Amplitude/Span issue

Question asked by andyTPE on Mar 17, 2011
Latest reply on Mar 31, 2011 by tabbott
I have an N9030A with f/ware A.07.04

I am trying to make some IM measurements, so the input signal to the spectrum analyzer are two tones separated by 1 MHz with a centre frequency of 1 GHz (vary centre frequency 1- 6 GHz in 1 GHz steps).

The signal generation 10 MHz is used as the reference to the N9030A (i.e. the source and receivers are locked together)

I have my front end attenuator set to 20 dB.  Given that my IM products are low down, I have the RBW=1 Hz and the span set to ~5 kHz.  Under this configuration the SA is using the FFT sweep mode.  I am using a Pk detector.  There are 1001 pts in the frequency sweep.

Now, with the span set to 5 kHz, my IM level measures -98 dBm.  If I change the span (LEAVING ALL OTHER SETTINGS ALONE), the measured IM level now measures -108 dBm.  I left the sweep time autocoupled, so the sweep time changes slightly between the two span settings.

I would have thought that the amplitude of my IM tone would be independent of the span.

There is no mention in the A.07.06 firmware release of this being a known bug or that it has been fixed. 

Can someone explain to me why when I change the span my tone changes by 10 dB?  Is this a bug, is it a measurement limitation or do I have some conflicting settings that is causing this?

Thank you,