信号与系统(第1章 信号与系统分析导论).pptVIP

Chap.1 Introduction to Signals and Systems Chap.1 Introduction to Signals and Systems 1.1 Description and Classificationof Signals (信号的描述与分类) Definition Description of Signals信号的定义与描述 What is a Signal (信号)? A Signal is formally defined as a function of one or more variables that conveys information on the nature of a physical phenomenon. 信号是一个或多个变量的函数，携带着某个物理现象的信息。 Definition Description of Signals信号的定义与描述 What is a Signal (信号)? Definition Description of Signals信号的定义与描述 What is a Signal (信号)? Definition Description of Signals信号的定义与描述 THE INDEPENDENT VARIABLES Can be continuous. Can be discrete Can be 1-D, 2-D, ??? N-D For this course: Focus on a single (1-D) independent variable which we call “time”. Definition Description of Signals信号的定义与描述 Mathematical Model of Signals 信号的数学模型： 时间函数，用解析式或图形表示 Example 1 — A Speech signalIts amplitude varies with time, depending on the spoken word and who speaks it.It’s a one-dimensional signal, the independent variable is “time”. Example 2 — Electrocardiogram (ECG) Signal Represent the electrical activity of the heart.It’s a one-dimensional signal, the independent variable is “time”. Classification Property of Signals信号的分类和特性 按信号的确定性 { sin with unifrnd(10%) % signal sin with unifrnd Periodic Signals (周期信号) Aperiodic Signals (非周期信号) 电信号f(t)的功率特性: 能量信号与功率信号 能量信号与功率信号 Chap.1 Introduction to Signals and Systems 1.2 Description and Classification of Systems系统的描述与分类 What is a system ? (Definition) A System is formally defined as an entity that manipulates one or more signals to accomplish a function, thereby yielding new signals. 系统——若干相互作用和相互依赖的事物组合而成的具有特定功能的整体 What is a system ? (Definition) E.g., Communication Systems(通信系统)、 Power Systems(电力系统)、Automatic Control Systems、 An RLC circuit、An edge detection algorithm for medical images …… 可以把系统理解为对信号进行传输、处理和存储的一种装置。 What is a system ? (Definition) For the most part, our view of systems will be from an input-output perspective: A system responds to applied input sign