I have found in the literature a "time-variant signal" term , but I could not understand what that's mean. I know that there is "time-variant systems", but this is the first time, which I see a time-variant signal term. Any one has an idea what this term means ?
Some suggests that this term is related to non-stationary signal, which it's spectrum changes over time. Is this right?
P.S: I have added the EEG tag because this term, is used widely to describe the EEG signals