I am working on FFT based spectrum analyser and I am not sure how to proceed calculating the RBW.
According to the document (page 20) in the link, RBW described as $k \frac{f_s}N$ where $f_s$ sampling frequency, $N$ FFT size and $k$ is window coefficent.
Since $\frac{f_s}N$ is simply frequency resolution, is there a way to calculate $k$ coefficent for different window functions?
I tried to check the book in the references but I couldn't find the information.