- Gary November 13, 2019 at 6:33 pm
Would 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.
Andrew November 14, 2019 at 7:44 am
- This reply was modified 4 years ago by Andrew.
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.
Let me know if you have follow up questions.
AndrewGary November 14, 2019 at 2:31 pm
Thank 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?
AndrewModeratorAndrew November 15, 2019 at 10:31 am
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.
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