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1、1,Chapter 6Time and Frequency Characterizationof Signals and Systems,2,Time-Domain:,Frequency-Domain:,6.1 The Magnitude-Phase Representation（幅度-相位）of the Fourier Transform,Magnitude,Energy-Density,3,6.2 The Magnitude-Phase Representation of the Frequency Response of LTI Systems,Gain,Phase Shift,1.Li
2、near Phase,2.Nonlinear Phase,4,Homework:6.5 6.23,5,6.5 Consider a continuous-time ideal bandbass filter whose frequency response is,If is the impulse response of this filter,determine a function such that,(b)As is increased,does the impulse response of the filterget more concentrated or less concent
3、rated about the origin?,Solution,(b)It will get more concentrated about the origin.,(a),6,(b),where T is a constant.,7,(c),8,Chapter 7 Sampling,9,10,Homework:7.1 7.2 7.3 7.6 7.9,7.3 The Effect of Undersampling:Aliasing 欠采样 混叠,11,7.1 A real-valued signal is known to be uniquely determined by its samp
4、les when the sampling frequency is.For what values of is guaranteed to be zero?,12,7.2 A continuous-time signal is obtained at the output of an ideal lowpass filter with cutoff frequency.If impulse-train sampling is performed on,which of the following sampling periods would guarantee that can be rec
5、overed from its sampled version using an appropriate lowpass filter?(a)T=0.510-3(b)T=210-3(c)T=10-4,(a)and(c),Sampling interval,13,7.3 Determine the Nyquist rate corresponding to each of the following signals:,14,Nyquist rate,maximum sampling interval,15,16,例 在如图1所示系统中,输入信号 的频谱如图2所示。已知，要求：,画出图中信号 和
6、的频谱；确定T的取值范围，以使信号 能从 中恢复。,17,Chapter 8 Communication Systems,18,19,Homework:8.1 8.3 8.22,20,21,Solution,22,8.22In Figure(a),a system is shown with input and outputThe input signal has the Fourier transform shown in Figure(b)Determine and sketch.,Figure(a),Figure(b),23,24,例 如图所示的系统中，已知输入信号 的傅立叶变换 如图1
7、所示，且。要求：,图1,画出图2中A、B、C各点的信号频谱；说明这是一个做什么用的系统。,25,例 如图所示系统中，,若输入信号,，试分别A、B、C各点信号,的频谱。,26,Example 4 In Figure(a),a system is shown with input signal and output signal.If the following information are given.,1.Determine,2.Determine the impulse response of the whole system.,If the input signal,determine the output signal,27,28,29,30,31,If is real,even,2.If is real,odd,32,Solution:,33,2.,3.,
