电子科技大学电子工程学院：《信号与系统》课程教学资源（PPT课件讲稿，英文版）Chapter 6 Time and Frequency Characterization of Signals and Systems

Chapter 6 Time and frequency characterization of Signals and Systems

1 Time and Frequency Characterization of Signals and Systems Chapter 6

Chapter 6 Time and Frequency Characterization 56.1 The Magnitude-Phase Representation (幅度-相位) of the fourier transform 产+o Xo olde 2丌 XGo)=rGjoyelzrvo X(io)— Magnitude Energy-Density xX(jo)—Phae 2

2 Chapter 6 Time and Frequency Characterization §6.1 The Magnitude-Phase Representation （ 幅度-相位） of the Fourier Transform ( ) ( ) ( )   j X j X j X j e  = ( ) ( )    x t X j e d j t 2 1  + − = X(j) ——Magnitude ( ) 2 X j ——Energy-Density X j ( ) ——Phase

Chapter 6 Time and Frequency Characterization ,(t)=4cos 2+cos 6zt cos 2nt+4 cos 67t

3 x (t) 4cos2t cos6t 1 = + x (t) cos2t 4cos6t 2 = + Chapter 6 Time and Frequency Characterization

Chapter 6 Time and Frequency Characterization X1(o) sin t →x X2(o) 11-10-90910110 带哪带 卜带 sin t 2-cos 1Ot

4 Chapter 6 Time and Frequency Characterization -1 0 1 ω 1 X (j) 1 ( ) t t x t  sin 1 = -11 -10 –9 0 9 10 11 ω 1 X (j) 2 ( ) t t t x t cos10 sin 2 2  =

Chapter 6 Time and Frequency Characterization x(t)=1+cos(2nt+Φ1)+cos(4xt+Φ2)+cos(67t+Φ3) Φ1=①,=①3=0 ①1=4,Φ2=8.3=12 A ①1=6,①2=-27①3=0.93 ①1=12,①2=41,3=-72

5 ( ) cos( ) cos( ) cos( ) 1 2 3 1 2 1 2 4 6 2 3 x t t t t = + + + + + +       0 1 = 2 = 3 = 4, 8, 12 1 = 2 = 3 = 6, 2 .7, 0.93 1 2 3  =  = −  = 1.2, 4.1, 7.2 1 2 3  =  =  = − Chapter 6 Time and Frequency Characterization