《信号与系统教学资料》2-Signals and Systems.pptVIP

* * * * * * * * * * * * * * * * * * * * * Signals and Systems Spring 2014 Lecture #2 6, 11 March, 2014 Chen Zubin (陈祖斌) Room 304, Geology Palace, 0431 czb@jlu.edu.cn 1. Some examples of systems 2. System properties and examples a) Causality b) Linearity c) Time invariance Signals and Systems 2# 1. Some examples of systems A system is a set of elements (often called components instead) and relationships which are different from relationships of the set or its elements to other elements or sets. 系统：为实现规定功能以达到某一目标而构成的相互关联的一个集合体或装置(部件)。 1. Some examples of systems For the most part, our view of systems will be from an input-output perspective: A system responds to applied input signals, and its response is described in terms of one or more output signals 1. Some examples of systems Interconnection of two systems: Series (Cascade) Interconnection Parallel Interconnection Series- Parallel Interconnection Block Diagrams 1. Some examples of systems ?An important concept is that of interconnecting systems —To build more complex systems by interconnecting simpler subsystems —To modify response of a system ?Signal flow (Block) diagram Feedback Interconnection I 1. Some examples of systems Ex. #1: RLC circuit 1. Some examples of systems Ex. #2: Mechanical system Force Balance: 1. Some examples of systems Observation: 1). A very rich class of systems (but by no means all systems of interest to us) are described by differential and difference equations. 2). Such an equation, by itself, does not completely describe the input-output behavior of a system: we need auxiliary conditions (initial conditions, boundary conditions). 3). In some cases the system of interest has time as the natural independent variable and is causal. However, that is not always the case. 4). Very different physical systems may have very similar mathematical descriptions. 1. Some examples of systems 2. System properties and examples a) Causality b) Linearity