improving result of FFT

Dear fellows i want to achieve good frequency resolution by adding this command in my code n = 2^nextpow2() but i dont know how to add in my code can anybody help me please.please don't change sampling frequency=36000 and bode=1000.

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;

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,abs(y))

title('FFT')

xlabel('frequency')

ylabel('amplitude')

figure(3)

z=y;

z(abs(fvec)>=50& abs(fvec)<=150)=0

plot(fvec,abs(z))

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')

Answer 1

[Daniel M]

You'll want to use it as the second input to the fft. This will affect your frequency vector fvec though.

n = 2^nextpow2(N);
y = fftshift(fft(x2,n)); % you can choose to normalize x2 by 1/n if you want

[imran khan]

i have tried but my program gives an error.

Error using plot

Vectors must be the same lengths.

Error in vlc (line 32)

plot(fvec,abs(y))

i recieve this error

[Daniel M]

Yes I said that would happen because you're working with n now not N.

[imran khan]

Dear Daniel M you have inspect correct mistake,will you please tell me which will be my new range of fvec

[Daniel M]

You can follow the second example on the document page for fft. It will demonstrate it more clearly than I will here.

[imran khan]

Dear danieli have taken the idea from matlab example which you send me in your link and i modified it but the problem is that i can't rectify me error