Time-Frequency Operators

Abstract

The fundamental idea of time-frequency analysis is to understand and describe how the frequency content of a signal is changing in time [20, 18]. By a signal one means a function of time, for example the electric and magnetic fields, pressure, voltage etc. Time functions are called wave forms or signals. We shall denote the signal by s(t). Examples of man-made signals whose frequencies are clearly changing in time are music and human speech where indeed it is the changing frequencies that are the essence of the signals.