problem to make fft

hello i have this code and i want to make the fft for it to make the same bits as i start with can u help me?>

thanks alot

clear all

N=10;
fs=1e6;
T=1e-3;

% random signal
bit=randint(20,1);     % 20 bits 0 or 1  1 x 20

% serial-to-parallel converter
par=reshape(bit,2,10);        % 2 x 10  2 bits for sym

% mapper
sym=par'*[2;1];       % multiplay for mapper 00-0 01-1 10-2 11-3
phase=[-3*pi/4,3*pi/4,-pi/4,pi/4];
phase_sym=phase(sym+1); % every sym gets phase for example pi/4 will get '3'

% IFFT
for k=0:N-1
    i=1
    for t=1/fs:1/fs:T
        x(k+1,i)=cos((2*pi*k*t)/T+phase_sym(k+1))+j*sin((2*pi*k*t)/T+phase_sym(k+1));
        i=i+1
   end
end

[Jonas Reber]

isn't it true that you need 2^N samples to calculate the fft / ifft?

[itsik]

ok so if i will sample the function with 1024 points how do i make the oposite fft to find the bits?

[Jonas Reber]

why exactly is ifft (matlab function) not an option for you?

[Walter Roberson]

Jonas: no, 2^N is not required for fft / ifft. The size has to do with efficiencies in the calculation, but other sizes can still be calculated. There are even sizes that are faster to calculate than 2^N

[itsik]

fist of all i want to thank you for your help

supposed thats i use ifft function :

ifft(phase_sym,1024) ( sampling of 1024)

and then i use the fft function , im getting a matrix of

1x1024

so my question is, how i can get the original matrix

(1X10 of phase_sym) back

thank you all

[itsik]

anyone , please ?

Answer 1

[Yella]

Heyy

Check this code

x=[1 2 3 4 5 6]; y=fft(x,512) z=ifft(y)

and u observe that x=z(1:1:length(x))

the first elements of the ifft is the signal the other elemnts in the matrix are made zero..