problem in plotting figure

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imran khan
imran khan 2019-11-7
评论： imran khan 2019-11-12
Dear fellows,i have modified code but i have problem in plotting the last figure(4) and problem is in this line plot(tvec,abs(zifft)).Problem was in my resolution in FFT.Can anyone edit my code please.
clc,close all,clear all
codn=100;
% fc=6e+3;
fs=36000;
bode=1000;
code=round(rand(1,codn));
code_len=round(1/bode/(1/fs))
for ii=1:codn
x((ii-1)*code_len+1:code_len*ii)=code(ii)
end
x2 = x-(1/2) % get rid of most of the dc peak
% set up time and frequency arrays
length(x)
N = length(x)
delt = 1/fs;
delf = fs/N;
tvec = (1:N)*delt;
n = 2^nextpow2(N);
fvec = (-n/2:n/2-1)*delf ; % shifted frequency array
figure(1)
plot(tvec,x2(1,:)+0.5)
title('orignal baseband')
xlabel('time');
ylabel('amplitude')
ylim([-1 1.5]);
y = fftshift(fft(x2,n));
z=abs(y);
figure(2)
plot(fvec,z)
title('FFT')
xlabel('frequency')
ylabel('amplitude')
figure(3)
z=y;
z(abs(fvec)>=50& abs(fvec)<=150)=0
plot(fvec,abs(y))
xlabel('frequency removed from 50 to 150 HZ');
ylabel('amplitude')
figure(4)
zf=fftshift(z)*n;
zifft=ifft(zf)+0.5;
plot(tvec,abs(zifft))
ylim([-1 1.5])
title('recovered signal')
xlabel('time');
ylabel('amplitude')

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回答（1 个）

KALYAN ACHARJYA
KALYAN ACHARJYA 2019-11-7
编辑：KALYAN ACHARJYA 2019-11-8
In the line no 44, see both variable have different lengths, how can plot two different lengths vectors
here
plot(tvec,abs(zifft))
##
>> whos tvec
Name Size Bytes Class Attributes
tvec 1x3600 28800 double
>> whos zifft
Name Size Bytes Class Attributes
zifft 1x4096 32768 double
Do change the code/equations, ensure that, in any plot all vectors must be same length.
Please check with back approach and see length of required variables why vectors reflects those having different lengths.
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KALYAN ACHARJYA
KALYAN ACHARJYA 2019-11-11
@Imran
Is this?
figure(4)
y=fftshift(fft(x2,length(tvec)));
z=y;
z(abs(fvec)>=50 & abs(fvec)<=150)=0
zf=fftshift(z)*n;
zifft=ifft(zf)+0.5;
plot(tvec,abs(zifft))
%ylim([-1 1.5])
title('recovered signal')
xlabel('time');
ylabel('amplitude')
56.png
imran khan
imran khan 2019-11-12
no dear its not right.In time domain my signal should be close to figure(1) but with little bit distortion

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