Forums › BB Series Discussions › Can you provide the 6 dB BW and NENBW for the Nuttall and Flattop BB60 windows?
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Gary.
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GaryParticipantWould Signalhound be willing to provide the 6 dB BW and normalized equivalent noise bandwidth (NENBW) for the Nuttall and Flattop windows? This would better facilitate comparison with other systems, most of which use these two parameters to measure RBW.
Thanks!
AndrewModerator- This reply was modified 5 years, 5 months ago by
Andrew.
Hi Gary,
We use the Nuttall window at the link below. It has an ENBW of 2.02 bins and 6 dB BW of ~2.78 bins.
For the BB60C and SA series devices and the flattop window, we take a variable bandwidth approach and build a flattop with the necessary bandwidth that meets the users RBW request in combination with the FFT sizes we have available. Because of this, the ENBW and 6dB bandwidth will change based on current configuration.
For the SM200, we use a flattop that has an ENBW of 3.78 bins and 6dB bandwidth of 4.9 bins.
Regardless of window chosen, the window bandwidth is taken into account when choosing FFT size, and zero-padding length when a user requests a specific RBW. This ensures consistency in RBW.
https://en.wikipedia.org/wiki/Window_function#Nuttall_window,_continuous_first_derivative
Let me know if you have follow up questions.
Regards,
Andrew
GaryParticipantThank you for the response. I’m confused, however. According to the Signalhound API manual, you use the 3 dB points to create the variable-width RBWs. But the value “2.02” for the Nuttall also matches the value for the table at the end of the API manual. That is the ENBW. The 3 dB value, according to my calculations, is around 1.9 bins for your Nuttall.
Any idea what I’m misunderstanding?
AndrewModeratorHi Gary,
Sorry, correction, we use the ENBW for the RBW calculation for all windows except the adjustable flat-top window that is used in the SA and BB devices, but in this case, the 3dB BW should be very close to the ENBW.
Regards
GaryParticipant- This reply was modified 5 years, 5 months ago by
Gary.
Ah! Got it! Thank you, Andrew!
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