Basic Concepts in Signals and Systems

摘要

In this article, basic concepts in signals and systems will be presented. Starting with the definition of linear systems, some elementary signals are introduced, which is followed by the notion of time-invariant systems. Signals and Systems are then coupled through impulse response, convolution, and response to exponential signals. This naturally leads to Fourier series representation of periodic signals and consequently, signal representation in the frequency domain in terms of amplitude and phase spectra. Linear system response to periodic signals, discussed next, is then easy to understand. To handle non-periodic signals, Fourier transform is introduced by viewing a non-periodic function as the limiting case of a periodic one, and its application to linear system analysis is illustrated. The concepts of energy and power signals and the corresponding spectral densities are then introduced.