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Unformatted text preview: 17 depend on ©     © ¦   © !  #  #  #    rectangular Barlett Hann Hamming Blackman Kaiser , ¡¤ sidelobe level dB £ ¢ mainlobe width ¦ window ¡ ¢ Window Properties 0 1.33 3.86 4.86 7.04 – Tolerances (ripple) in passband and stopband are not separately determined. ECE 600 FIR Design T.H.E OHIO S ATE T UNIVERSITY Slide # 8 Window-based Design Steps: Generalized Linear Phase FIR Filters 1. Specify ideal frequency response 2. Select window to satisfy passband and stopband ripple specs ¦ to satisfy transition bandwidth (and noting constraints of types I–IV)   3. Select order ©  ¨ ¥§ £ ¤ £ IDTFT ¢ ¤ ¡ ¤  ¢¡   §¥ © ¦ §¥ ¨ delay (for causal final result), and 4. Compute ideal impulse response with truncate via multiplication with shifted window sequence 5. Compute frequency response and compare to specifications  6. Iterate to meet specs with lowest order to affect transition width (and adjust Kaiser ) ©  (a) adjust order (b) adjust band-edge frequencies to shift magnitude response ECE 600 FIR Design T.H.E OHIO S ATE T UNIVERSITY Slide # 9 FIR Design Example 1 Specifications:           ¥  £  ¥ ¡ ¥ ¥ ¤ ¡ ¥ ¡ ¥ ¥ ¥  § §  Linear phase ECE 600 FIR Design T.H.E OHIO S ATE T UNIVERSITY Slide # 10 FIR Design Example 1, continued As=40;deltap=0.02;op=0.2;os=0.3; N=60;h=fir1(N,0.2494,hann(N+1)); % or >> h=sin(0.249*pi*[-30:30])./(pi*[-30:30]);h(31)=0.2494;h=h.*hann(61)'; [H,omega]=freqz(h,1,1024); subplot(2,1,1);plot(omega/pi,20*log10(abs(H)));grid;axis([0 1 -70 10]) subplot(2,2,3);plot(omega/pi,20*log10(abs(H)));grid;hold on; plot([0 op],20*log10(1+deltap)*[1 1],'r',[0 op],20*log10(1-deltap)*[1 1],'r'); axis([0.12 0.22 -0.5 0.5]);hold off; subplot(2,2,4);plot(omega/pi,20*log10(abs(H)));grid;hold on; plot([os 1],-40*[1 1],'r');axis([0.295 0.315 -50 -30]);hold off; 10 0 −10 −20 −30 −40 −50 −60 −70 0 0.1 0.2 0.3 0.4 0.5 0.5 0.6 0.7 0.8 0.9 1 0.305 0.31 0.315 −30 −35 0 −40 −45 −0.5 0.12 ECE 600 FIR Design 0.14 0.16 0.18...
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This note was uploaded on 01/15/2014 for the course ECE 600 taught by Professor Clymer,b during the Winter '08 term at Ohio State.

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