Is it possible to detect the low and high frequency ratio of a PSD if you are working on simulink instead of workspace?

I'm a beginner when it comes to signal processing. What I want to do, is to set the low and high frequency ratio as the output of my simulink model. However I've observed in simulink that the PSD block serves as a scope. So it only has an input but no output. (I can't detect lf,hf,vlf)

Now, I've tried the periodogram but I'm not sure whether it is indeed the low and high frequency of the power spectrum that I'm getting. After the psd block, I attached a passband filter (two: one for LF andf HF) to get their values then I placed a divide block for it to be (LF/HF).

Actually the reason for that, is I want my simulink model to be merged in a microcontroller. What happens is that whatever process my simulink does, it will now be done by my microcontroller.

Is my signal already in the PSD form after it went through Hamming,FFT,magnitude of FFT? or am I doing it the wrong way?

PLEASE HELP ME!