34 lines
1.8 KiB
Matlab
Executable File
34 lines
1.8 KiB
Matlab
Executable File
% ##################################################################################
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% ## Loesung: Seitenbanddaempfung des Blackman-Fenster ##
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% ##################################################################################
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NFFT=2^10;
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f_bl032= blackman(32); aF_bl032= abs(fft(f_bl032,NFFT)/sum(f_bl032));
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f_bl064= blackman(64); aF_bl064= abs(fft(f_bl064,NFFT)/sum(f_bl064));
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f_bl128= blackman(128); aF_bl128= abs(fft(f_bl128,NFFT)/sum(f_bl128));
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fT = 0:1/NFFT:1-1/NFFT;
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% Berechnung der minimalen Sperrdaempfung a_{min}:
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% Os := Omega_s/(2*pi); n_s: Sperrbereich-Indices: n_s+1<=n<=NFFT+1-n_s
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Os=3/32; n_s=round(NFFT*Os); a032=20*log10(max(aF_bl032(n_s+1:NFFT+1-n_s)));
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Os=3/64; n_s=round(NFFT*Os); a064=20*log10(max(aF_bl064(n_s+1:NFFT+1-n_s)));
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Os=3/128; n_s=round(NFFT*Os); a128=20*log10(max(aF_bl128(n_s+1:NFFT+1-n_s)));
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figure; plot(fT, 20*log10(aF_bl032)); hold on; axis([0 1 -180 10]);
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text(0.41,a032,sprintf('a_{min} = %3.1f dB',-a032));
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plot([0 0.39], [a032 a032], '--');
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title('|Norm. Spektralfunktion| des Blackmanfensters: N=32');
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ylabel('|F(exp(j*Om.))/F(exp(j*0))| in dB'); xlabel('Omega/2pi = f T');
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figure; plot(fT, 20*log10(aF_bl064)); hold on; axis([0 1 -180 10]);
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text(0.41,a064,sprintf('a_{min} = %3.1f dB',-a064));
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plot([0 0.39], [a064 a064], '--');
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title('|Norm. Spektralfunktion| des Blackmanfensters: N=64');
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ylabel('|F(exp(j*Om.))/F(exp(j*0))| in dB'); xlabel('Omega/2pi = f T');
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figure; plot(fT, 20*log10(aF_bl128)); hold on; axis([0 1 -180 10]);
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text(0.41,a128,sprintf('a_{min} = %3.1f dB',-a128));
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plot([0 0.39], [a128 a128], '--');
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title('|Norm. Spektralfunktion| des Blackmanfensters: N=128');
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ylabel('|F(exp(j*Om.))/F(exp(j*0))| in dB'); xlabel('Omega/2pi = f T');
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% ##### EOF #####
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