实验四线性时不变离散时间系统的频域分析.doc

Name:Chen yifan 20112121006 Section: Laboratory Exercise 4 LINEAR, TIME-INVARIANT DISCRETE-TIME SYSTEMS: FREQUENCY-DOMAIN REPRESENTATIONS 4.1 TRANSFER FUNCTION AND FREQUENCY RESPONSE Project 4.1 Transfer Function Analysis Answers: Q4.1 The modified Program P3_1 to compute and plot the magnitude and phase spectra of a moving average filter of Eq. (2.13) for 0 ? 2( is shown below: Insert program code here. Copy from m-file(s) and paste. w=0:pi/511:2*pi; M=input(M= ); num=ones(1,M)/M; h=freqz(num,1,w); subplot(2,1,1); plot(w/pi,abs(h));grid; title(H(e^{j\omega})幅度谱); xlabel(\omega/\pi);ylabel(振幅); subplot(2,1,2); plot(w/pi,angle(h));grid; title(相位谱 H(e^{j\omega})); xlabel(\omega/\pi);ylabel(以弧度为单位的相位); This program was run for the following three different values of M and the plots of the corresponding frequency responses are shown below: Insert MATLAB figure(s) here. Copy from figure window(s) and paste. The types of symmetries exhibited by the magnitude and phase spectra are due to - The type of filter represented by the moving average filter is M=3 - M=10; M=20; The results of Question Q2.1 can now be explained as follows - By the graph, you can see that it represents a low-pass filter. Q4.2 The plot of the frequency response of the causal LTI discrete-time system of Question Q4.2 obtained using the modified program is given below: Insert MATLAB figure(s) here. Copy from figure window(s) and paste. w=0:pi/511:pi; num=[0.15 0 -0.15]; den=[1 -0.5 0.7]; h=freqz(num,den,w); subplot(2,1,1); plot(w/pi,abs(h));grid; title(H(e^{j\omega})幅度谱); xlabel(\omega/\pi);ylabel(振幅); subplot(2,1,2); plot(w/pi,angle(h));grid; title(相位谱 H(e^{j\omega})); xlabel(\omega/\pi); ylabel(以弧度为单位的相位); The type of filter represented by this transfer function is - It says bandpass filter is obtained by diagrams can be BPF Q4.3 The plot of the frequency response of the causal LTI discrete-time system of Question Q4.3 obtained using the modified program is given below: I