Hello bbowar,
We use custom size flattop windows to achieve our RBWs, which means the noise bandwidth will be dependent on the current RBW. You will need to calculate the noise bandwidth of our window function like this.
// rbw = current resolution bandwidth
// log2 = log base 2
// pow2 = 2 ^ value
double min_bin_sz = rbw / 3.2;
double min_fft = 486111.111 / min_bin_sz;
int order = (int)ceil(log2(min_fft));
int fft_size = pow2(order);
double noise_bw = (rbw * (double)fft_size) / 486111.111;
This could probably be simplified a bit more as well.
Just to verify, here is how we calculate channel power in our software to compare against.
1) Set Average Detector and Power video units
2) Get sweep
3) Convert frequency range to power units (W)
4) Sum frequency range of interest in power units
5) Divide sum by the window bandwidth (or noise bandwidth) as calculated above.
Let me know if you have any further questions
Regards,
A.J.
