文档介绍：Chapter 2. Discrete-Time Signals and Systems
Main Contents
Important types of signals and their operations
Linear and shift-invariant system
Easier to analyze and implement
The convolution and difference equation representations
Representations and implementation of signal and systems using MATLAB
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Some concepts
Digital signal processing: It is a transformation for signals that are discrete in both amplitude and time.
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A: Discrete-time signals: sequences
Analog and discrete signals
analog signal
t represents any physical quantity, time in sec.
Discrete signal: discrete-time signal
n is integer valued, represents discrete instances in times, and T is the sampled period (its reciprocal is the sampling frequency)
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In Matlab, a finite-duration sequence representation requires two vectors, and each for x and n.
Example:
Question: whether or not an arbitrary infinite-duration sequence can be represented in MATLAB?
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. Types of sequences
1. Unit sample (Impulse) sequence
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Representation in matlab
A: n=[n1:n2];
x = zeros(1,n2-n1+1); x(n0-n1+1)=1;
B: n=[n1:n2]; x = [(n-n0)==0]; stem(n,x);
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2. Unit step sequence
A: n=[n1:n2]; x=zeros(1,n2-n1+1); x(n0-n1+1:end)=1;
B: n=[n1:n2]; x=[(n-n0)>=0];
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3. Real-valued exponential sequence
For Example:
n=[0:10]; x=().^n; stem(n,x)
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4. Complex-valued exponential sequence
Attenuation: 衰减因子
frequency in radians:ω0
For Example: n=[0:10]; x=exp((2+3j)*n);
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