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
