6 Time and Frequency Characterization of Signals and Systems 6.0 Introduction Meanings of the Fourier Transform of a CT signal Magnitude-Spectrum and Phase-Spectrum ( The magnitude and phase angle of the CTFT ) Meanings of the Frequency response of a LTI system The magnitude and phase shift of the frequency response (The magnitude-frequency and phase-frequency characteristics) The distortionless transmission-system The Time and Frequency-domain properties of Frequency-Selective Filters Time and Frequency-domain properties of First and Second-Order systems

6.1 The Magnitude-Phase Representation of The Fourier Transform

Magnitude-Spectrum/ The magnitude of the CTFT : The complex magnitude of the frequency component is: The relative complex magnitude is

Phase-Spectrum/ The phase angle of the CTFT : The complex magnitude of the frequency component is: The relative complex magnitude is

xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); clear all; t=-4:0.05:4; xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); plot(t,xt,'b'); xlabel('t'); hold on y1t=cos(0.56*pi*t-pi/3)+cos(0.28*pi*t-2*pi/3)+cos(t-pi/2); plot(t,y1t,'r'); y2t=cos(0.56*pi*(t-0.5*pi/2))+cos(0.28*pi*(t-0.5*pi/2))+cos(t-0.5*pi/2); plot(t,y2t,'c');title('x(t),y1(t),y2(t)');hold off

clear all; t=-4:0.05:4; xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); plot(t,xt,'b'); xlabel('t'); hold on y1t=0.25*cos(0.56*pi*t)+0.5*cos(0.28*pi*t)+cos(t); plot(t,y1t,'r') y2t=cos(0.56*pi*t)+0.5*cos(0.28*pi*t)+0.25*cos(t); plot(t,y2t,'c');title('x(t),y1(t),y2(t)'); hold off

6.2 The Magnitude-Phase Representation of The Frequency Response of LTI Systems

The magnitude of the frequency response / The magnitude-frequency characteristic: The effect an LTI system has on the magnitude of the FT of a input signal is to scale it by the magnitude of the frequency response

The phase shift of the frequency response / The phase -frequency characteristic:

6.2.1 The distortionless transmission-system

6.2.1 The distortionless transmission-system

xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); clear all; t=-4:0.05:4; xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); plot(t,xt,'b'); xlabel('t'); hold on y1t=cos(0.56*pi*t-pi/3)+cos(0.28*pi*t-2*pi/3)+cos(t-pi/2); plot(t,y1t,'r'); y2t=cos(0.56*pi*(t-0.5*pi/2))+cos(0.28*pi*(t-0.5*pi/2))+cos(t-0.5*pi/2); plot(t,y2t,'c');title('x(t),y1(t),y2(t)');hold off

clear all; t=-4:0.05:4; xt=cos(0.56*pi*t)+cos(0.28*pi*t)+cos(t); plot(t,xt,'b'); xlabel('t'); hold on y1t=0.25*cos(0.56*pi*t)+0.5*cos(0.28*pi*t)+cos(t); plot(t,y1t,'r') y2t=cos(0.56*pi*t)+0.5*cos(0.28*pi*t)+0.25*cos(t); plot(t,y2t,'c');title('x(t),y1(t),y2(t)'); hold off

SAS实验三 线性失真的计算机仿真与分析 内容 1 无失真传输系统的概念，应满足的条件； 2 幅度失真的涵义，仿真分析； 3 相位失真的涵义，仿真分析； 4 幅度、相位失真的仿真分析； 5 总结 要求 1 理论分析完整、严谨； 2 仿真条件表述清晰，仿真结果具有说服力； 3 以学术论文格式写作。 文档类型：Word或PPT文档 文件名：学号_姓名_实验3