代码:

  1. %% ------------------------------------------------------------------------
  2. %% Output Info about this m-file
  3. fprintf('\n***********************************************************\n');
  4. fprintf(' <DSP using MATLAB> Problem 8.8 \n\n');
  5. banner();
  6. %% ------------------------------------------------------------------------
  7.  
  8. % digital iir highpass filter
  9. b = [1 -1];
  10. a = [1 -0.9];
  11.  
  12. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 Pole-Zero Plot')
  13. set(gcf,'Color','white');
  14. zplane(b,a);
  15. title(sprintf('Pole-Zero Plot'));
  16. %pzplotz(b,a);
  17.  
  18. % corresponding system function Direct form
  19. K = 1; % gain parameter
  20. b = K*b; % denominator
  21. a = a; % numerator
  22.  
  23. [db, mag, pha, grd, w] = freqz_m(b, a);
  24.  
  25. % ---------------------------------------------------------------------
  26. % Choose the gain parameter of the filter, maximum gain is equal to 1
  27. % ---------------------------------------------------------------------
  28. gain1=max(mag) % with poles
  29. K = 1/gain1
  30. [db, mag, pha, grd, w] = freqz_m(K*b, a);
  31.  
  32. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 IIR highpass filter')
  33. set(gcf,'Color','white');
  34.  
  35. subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -60 10]);
  36. set(gca,'YTickMode','manual','YTick',[-60,-30,0])
  37. set(gca,'YTickLabelMode','manual','YTickLabel',['60';'30';' 0']);
  38. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  39. xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');
  40.  
  41. subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 1 -100 10]);
  42. xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');
  43. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  44. set(gca,'YTickMode','manual','YTick',[0,1.0]);
  45.  
  46. subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);
  47. xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');
  48.  
  49. subplot(2,2,4); plot(w/pi, grd*pi/180); grid on; %axis([0 1 -100 10]);
  50. xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');
  51. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  52. %set(gca,'YTickMode','manual','YTick',[0,1.0]);
  53.  
  54. % Impulse Response
  55. fprintf('\n----------------------------------');
  56. fprintf('\nPartial fraction expansion method: \n');
  57. [R, p, c] = residuez(K*b,a)
  58. MR = (abs(R))' % Residue Magnitude
  59. AR = (angle(R))'/pi % Residue angles in pi units
  60. Mp = (abs(p))' % pole Magnitude
  61. Ap = (angle(p))'/pi % pole angles in pi units
  62. [delta, n] = impseq(0,0,50);
  63. h_chk = filter(K*b,a,delta); % check sequences
  64.  
  65. % ------------------------------------------------------------------------------------------------
  66. % gain parameter K=0.95
  67. % ------------------------------------------------------------------------------------------------
  68. h = ( 0.9.^n ) .* (-0.1056) + 1.0556 * delta;
  69. % ------------------------------------------------------------------------------------------------
  70.  
  71. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 IIR hp filter, h(n) by filter and Inv-Z ')
  72. set(gcf,'Color','white');
  73.  
  74. subplot(2,1,1); stem(n, h_chk); grid on; %axis([0 2 -60 10]);
  75. xlabel('n'); ylabel('h\_chk'); title('Impulse Response sequences by filter');
  76.  
  77. subplot(2,1,2); stem(n, h); grid on; %axis([0 1 -100 10]);
  78. xlabel('n'); ylabel('h'); title('Impulse Response sequences by Inv-Z');
  79.  
  80. [db, mag, pha, grd, w] = freqz_m(h, [1]);
  81.  
  82. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 IIR filter, h(n) by Inv-Z ')
  83. set(gcf,'Color','white');
  84.  
  85. subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -60 10]);
  86. set(gca,'YTickMode','manual','YTick',[-60,-30,0])
  87. set(gca,'YTickLabelMode','manual','YTickLabel',['60';'30';' 0']);
  88. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  89. xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');
  90.  
  91. subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 1 -100 10]);
  92. xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');
  93. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  94. set(gca,'YTickMode','manual','YTick',[0,1.0]);
  95.  
  96. subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);
  97. xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');
  98.  
  99. subplot(2,2,4); plot(w/pi, grd*pi/180); grid on; %axis([0 1 -100 10]);
  100. xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');
  101. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  102. %set(gca,'YTickMode','manual','YTick',[0,1.0]);
  103.  
  104. % --------------------------------------------------
  105. % digital IIR comb filter
  106. % --------------------------------------------------
  107. b = K*[1 0 0 0 0 0 -1];
  108. a = [1 0 0 0 0 0 -0.9];
  109.  
  110. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 Pole-Zero Plot')
  111. set(gcf,'Color','white');
  112. zplane(b,a);
  113. title(sprintf('Pole-Zero Plot'));
  114.  
  115. [db, mag, pha, grd, w] = freqz_m(b, a);
  116.  
  117. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 IIR comb filter')
  118. set(gcf,'Color','white');
  119.  
  120. subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -60 10]);
  121. set(gca,'YTickMode','manual','YTick',[-60,-30,0])
  122. set(gca,'YTickLabelMode','manual','YTickLabel',['60';'30';' 0']);
  123. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  124. xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');
  125.  
  126. subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 1 -100 10]);
  127. xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');
  128. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  129. set(gca,'YTickMode','manual','YTick',[0,1.0]);
  130.  
  131. subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);
  132. xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');
  133.  
  134. subplot(2,2,4); plot(w/pi, grd*pi/180); grid on; %axis([0 1 -100 10]);
  135. xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');
  136. set(gca,'XTickMode','manual','XTick',[0,0.25,0.5,1,1.5,1.75,2]);
  137. %set(gca,'YTickMode','manual','YTick',[0,1.0]);
  138.  
  139. % Impulse Response
  140. fprintf('\n----------------------------------');
  141. fprintf('\nPartial fraction expansion method: \n');
  142. [R, p, c] = residuez(b,a)
  143. MR = (abs(R))' % Residue Magnitude
  144. AR = (angle(R))'/pi % Residue angles in pi units
  145. Mp = (abs(p))' % pole Magnitude
  146. Ap = (angle(p))'/pi % pole angles in pi units
  147. [delta, n] = impseq(0,0,250);
  148. h_chk = filter(b,a,delta); % check sequences
  149.  
  150. % ------------------------------------------------------------------------------------------------
  151. % gain parameter K=0.95
  152. % ------------------------------------------------------------------------------------------------
  153. %h = 0.0211 * (( 0.9791.^n ) .* (2*cos(0.4*pi*n) + 2*cos(0.8*pi*n) + 1)) - 0.0556*delta; %L=5;
  154. h = -0.0176 * ( ( 0.9826.^n ) .* ( 2*cos(2*pi*n/3) + 2*cos(pi*n/3) + (-1).^n + 1) ) + 1.0556*delta; %L=6;
  155. % ------------------------------------------------------------------------------------------------
  156.  
  157. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 Comb filter, h(n) by filter and Inv-Z ')
  158. set(gcf,'Color','white');
  159.  
  160. subplot(2,1,1); stem(n, h_chk); grid on; %axis([0 2 -60 10]);
  161. xlabel('n'); ylabel('h\_chk'); title('Impulse Response sequences by filter');
  162.  
  163. subplot(2,1,2); stem(n, h); grid on; %axis([0 1 -100 10]);
  164. xlabel('n'); ylabel('h'); title('Impulse Response sequences by Inv-Z');
  165.  
  166. [db, mag, pha, grd, w] = freqz_m(h, [1]);
  167.  
  168. figure('NumberTitle', 'off', 'Name', 'Problem 8.8 Comb filter, h(n) by Inv-Z ')
  169. set(gcf,'Color','white');
  170.  
  171. subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -60 10]);
  172. set(gca,'YTickMode','manual','YTick',[-60,-30,0])
  173. set(gca,'YTickLabelMode','manual','YTickLabel',['60';'30';' 0']);
  174. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  175. xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');
  176.  
  177. subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 1 -100 10]);
  178. xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');
  179. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  180. set(gca,'YTickMode','manual','YTick',[0,1.0]);
  181.  
  182. subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);
  183. xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');
  184.  
  185. subplot(2,2,4); plot(w/pi, grd*pi/180); grid on; %axis([0 1 -100 10]);
  186. xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');
  187. set(gca,'XTickMode','manual','XTick',[0,0.25,1,1.75,2]);
  188. %set(gca,'YTickMode','manual','YTick',[0,1.0]);

  运行结果:

增益系数K

单个iir高通滤波器,零极点图

L=6阶梳状,系统函数部分分式展开

零极点的模和幅角

直接形式分子、分母系数直接求幅度谱、相位谱和群延迟

依据梳状滤波器系统函数部分分式展开,求逆z变换得到脉冲响应序列,由其求幅度谱、相位谱和群延迟,如下

直接形式求法和逆z变换求法,幅度谱、相位谱一致,但群延迟不同。

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