Time‐Frequency Analysis

A signal has one or more frequencies in it, and can be viewed from two different standpoints: Time domain and Frequency domain.

Time‐domain figure: how a signal changes over time
Frequency‐domain figure: how much of the signal lies within each given frequency band over a range of frequencies

Why frequency domain analysis? 

• To decompose a complex signal into simpler parts to facilitate analysis
• Differential and difference equations and convolution operations in the time domain become algebraic operations in the frequency domain
• Fast Algorithm (FFT)