This is a STFT diagram, I have got from my signal. I have used these command below:
My confusion arises because on the STFT diagram, I am seeing negetive magnitude -20DB. Usually on the examples of matlab central I have found all with positive magnitude and made senses to me. However, with my sample signal, I have go confused. the sampling frequency is 500000.
I have added the samplesignal.mat file for usage.
I will be really helpful if some one can guide me to understand what is going on over here.