10. ura (plan): obdelava signala

[alesB]

Naredili bomo najbolj osnovno obdelavo signala.

Kot primer bomo vzeli signal, ki je vsota sinusnih signalov treh frekvenc.
Ena je visoka, relativno majhne amplitude, zato njen prispevek izgleda kot motnja.

Postopek je naslednji: signal (s FFT) pretvorimo v spekter, spekter popravimo in
transformiramo nazaj (z IFFT) v popravljen signal.

Primer je na sliki spodaj:

bb.png (210.93 KiB) Viewed 1130 times

lpa

[alesB]

Code: Select all

# Octave 4.2.2, Mon Feb 13 18:06:01 2023 CET <ales@piko>
clc
uu=sigsum([1,2,3],[30,50,60],[0,0,0])
fs=1000;
ts=2;
tt=0:1/fs:(ts-1/fs);
uu=sigsum(tt,[1,2,3],[30,50,60],[0,0,0]);
uu
uu=sigsum(tt,[1,2,3],[30,50,60],[0,0,0]);
[tt,uu]
[tt;uu]
[tt;uu]'
[tt;uu]'
uu=sigsum(tt,[1,2,3],[30,50,60],[0,0,0]);
[tt;uu]'
plot(tt,uu)
plot(tt,uu,"linewidth",3);grid;
plot(tt(1:100),uu(1:100),"linewidth",3);grid;
plot(tt(1:100),uu(1:100),"linewidth",3);grid;
AA
uu=sigsum(tt,[1,2,3],[30,50,60],[0,0,0]);
fftuu=fft(uu);
bar(fftuu);grid;
bar(abs(fftuu));grid;
bar(abs(fftuu));
bar(abs(fftuu))
fftuu
abs(fftuu)>200
find(abs(fftuu)>200)
bar(abs(fftuu),"linewidth",3)
bar(abs(fftuu),"linewidth",3);grid;
bar(abs(fftuu)(1:100),"linewidth",3);grid;
bar(abs(fftuu)(1:500),"linewidth",3);grid;
bar(abs(fftuu)(1:300),"linewidth",3);grid;
bar(abs(fftuu)(1:200),"linewidth",3);grid;
ff=0:1/ts:(fs-1/ts);
bar(abs(fftuu)(1:300),"linewidth",3);grid;
bar(ff(1:200),abs(fftuu)(1:200),"linewidth",3);grid;
uu=sigsum(tt,[1,2,3],[30,50,60],[0,0,0]);
uu=sigsum(tt,[1,0.8,0.9,0.2],[30,50,60,533],[0,0,0]);
uu=sigsum(tt,[1,0.8,0.9,0.2],[30,50,60,533],[0,0,0,0]);
plot(tt(1:100),uu(1:100),"linewidth",3);grid;
plot(tt(1:200),uu(1:200),"linewidth",3);grid;
uu=sigsum(tt,[1,0.8,0.9,0.3],[30,50,60,533],[0,0,0,0]);
plot(tt(1:200),uu(1:200),"linewidth",3);grid;
fftuu=fft(uu);
bar(abs(fftuu)(1:300),"linewidth",3);grid;
plot(tt(1:200),uu(1:200),"linewidth",3);grid;
bar(ff(1:200),abs(fftuu)(1:200),"linewidth",3);grid;
bar(ff(1:700),abs(fftuu)(1:700),"linewidth",3);grid;
bar(ff(1:700),abs(fftuu)(1:800),"linewidth",3);grid;
bar(ff(1:800),abs(fftuu)(1:800),"linewidth",3);grid;
bar(ff(1:1000),abs(fftuu)(1:1000),"linewidth",3);grid;
bar(ff(1:1200),abs(fftuu)(1:1200),"linewidth",3);grid;
fs=10000;
ts=2;
tt=0:1/fs:(ts-1/fs);
ff=0:1/ts:(fs-1/ts);
uu=sigsum(tt,[1,0.8,0.9,0.3],[30,50,60,533],[0,0,0,0]);
plot(tt(1:200),uu(1:200),"linewidth",3);grid;
plot(tt(1:1000),uu(1:1000),"linewidth",3);grid;
plot(tt(1:2000),uu(1:2000),"linewidth",3);grid;
fftuu=fft(uu);
bar(ff(1:1200),abs(fftuu)(1:1200),"linewidth",3);grid;
bar(ff(1:12000),abs(fftuu)(1:12000),"linewidth",3);grid;
bar(ff(1:22000),abs(fftuu)(1:22000),"linewidth",3);grid;
bar(ff(1:20000),abs(fftuu)(1:20000),"linewidth",3);grid;
bar(ff(1:1200),abs(fftuu)(1:1200),"linewidth",3);grid;
find(abs(fftuu)>2000)
fft2=fftuu;
fft2(1067)=0;
bar(ff(1:1200),abs(fft2)(1:1200),"linewidth",3);grid;
bar(ff(1:1200),abs(fftuu)(1:1200),"linewidth",3);grid;
bar(ff(1:1200),abs(fft2)(1:1200),"linewidth",3);grid;
uu2=ifft(fft2);
uu2
uu2'
plot(tt(1:2000),real(uu2)(1:2000),"linewidth",3);grid;
find(abs(fft2)>2000)
fft2(18935)=0;
uu2=ifft(fft2);
plot(tt(1:2000),real(uu2)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu2)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu2)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu)(1:2000),"linewidth",3);grid;
plot(tt(1:2000),real(uu2)(1:2000),"linewidth",3);grid;
help save
help history_save 
help history
quit
# Octave 4.2.2, Mon Feb 20 17:45:14 2023 CET <ales@piko>