武汉大学数字信号实验三.doc

姓名:全权 学号：2013302530120 班级：信安四班 日期：5月8日 实验3离散时间系统-频域分析 实验内容： 3.1 DISCRETE-TIME FOURIER TRANSFORM(离散时间傅立叶变换) Project 3.1 DTFT Computation A copy of Program P3_1 is given below: % Program P3_1 % Evaluation of the DTFT clf; % Compute the frequency samples of the DTFT w = -4*pi:8*pi/511:4*pi; num = [2 1];den = [1 -0.6]; h = freqz(num, den, w); % Plot the DTFT subplot(2,1,1) plot(w/pi,real(h));grid title(Real part of H(e^{j\omega})) xlabel(\omega /\pi); ylabel(Amplitude); subplot(2,1,2) plot(w/pi,imag(h));grid title(Imaginary part of H(e^{j\omega})) xlabel(\omega /\pi); ylabel(Amplitude); pause subplot(2,1,1) plot(w/pi,abs(h));grid title(Magnitude Spectrum |H(e^{j\omega})|) xlabel(\omega /\pi); ylabel(Amplitude); subplot(2,1,2) plot(w/pi,angle(h));grid title(Phase Spectrum arg[H(e^{j\omega})]) xlabel(\omega /\pi); ylabel(Phase in radians); Insert program code here. Copy from m-file(s) and paste. Answers: Q3.1 The expression of the DTFT being evaluated in Program P3_1 is - The function of the pause command is - 暂停程序执行 Q3.2 The plots generated by running Program P3_1 are shown below: Insert MATLAB figure(s) here. Copy from figure window(s) and paste. The DTFT is a 周期性 function of ?. Its period（周期） is -____2π______ The types of symmetries(对称性) exhibited by the four plots are as follows: 实部周期为2π且对称，虚部周期为2π且为奇函数，幅度为2π且为偶函数，相位为2π且为奇函数 （指导说明：P3_1原始程序中的参数确定的系统函数为： ， 通过调整变量num，den，w观察频率响应的变化） Q3.3 The required modifications to Program P3_1 to evaluate the given DTFT of Q3.3 are given below: N=512; num = [0.7 -0.5 0.3 1]; den = [1 0.3 -0.5 0.7]; [h,w] = freqz(num,den,N); % Plot the DTFT subplot(2,1,1) plot(w/pi,real(h));grid title(Real part of H(e^{j\omega}));xlabel(\omega /\pi);ylabel(Amplitude);subplot(2,1,2) plot(w/pi,imag(h));grid title(Imaginary part of H(e^{j\omega}));xlabel(\omega /\pi);ylabel(Amplitude);pause subplot(2,1,1) plot(w/pi,abs(h));grid title(Magnitude Spectrum |H(e^{j\omega})|);xlabel(\omega /\pi);ylabel(Amplitude);subpl