信号与系统第二版第一章课件.pdf

Signals and Systems Chapter 1 Signals and systems Signals and Systems Contents Some of the elementary ideas related to the mathematical presentation of signals and systems Transformations of the independent variable of a signal Some of the most important and basic CT and DT signals Basic system properties Signals and Systems Signals The information in a signal is contained in a pattern of variation of some form. Signals and Systems Example: recording of speech Bird chirps Gong Signals and Systems Example: monochromatic pictures Signals and Systems Representation Signals are represented mathematically as functions of one or more independent variables Expression representation Example: x(t) = cost 0 j t x(t) = e 0 Graphical representation Signals and Systems 1.1 Continuous-time and discrete-time signals Continuous-time signals The independent variable is continuous Discrete-time signals Defined only at discrete-times Signals and Systems Signals and Systems A discrete –time signal may represent a phenomenon for which the independent variable is inherently discrete. A very important class of discrete- time signals arises from sampling of continuous-time signals.