MATLAB: Received signal not on sampling time

sample time

Hello all,

I have a sequence d of length N samples each of duration Ts. The channel I have will scale the received samples by a factor (1+a), which means that the received samples will not be on multiples of Ts but on multiples of Ts*(1+a). How can I capture this effect in MATLAB?

Thanks in advance

Best Answer

I’m not certain I completely understand what you want to do, but the Signal Processing Toolbox function resample may work.

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MATLAB: Frequency Selective Channel Coefficients in MATLAB

here is a start :

 Fs=800;
 fc=300; % Hz
 Ts=1/Fs;
 L=400;
 t=0:Ts:(L-1)*Ts;
 d=4; %  four signals per example,

tau is dependent on physical parameters, distance and coordinates, but i consider here a linear progressive phase, and the signals are sinusoidal :

 tau=(0:d-1);
 fm=0;
 for p=1:d
 fm=fm+exp(-j*2*pi*fc*tau(p))*sin(2*pi*t);
 end
 figure; plot(real(fm));

your assignment now is to replace the sin signals with the rectangular ones .

MATLAB: How to do this more efficiently

It isn't necessary to do the inequality test for every possible pair of kk and mm values. Since kk and mm are integers and Ts must surely be a positive number, your pair of inequalities is logically equivalent to

 kk-mm == d

where d = floor((tau(qq)-tau(pp))/Ts). Therefore you can simply add the appropriate vectors along corresponding diagonals of F. For large N, doing it this way should save quite a bit of computation time.

F=zeros(N);
for pp=1:Np
  for qq=1:Np
    d = floor((tau(qq)-tau(pp))/Ts);
    kk = max(d,0):min(N-1,N-1+d);
    mm = kk-d;
    theta=(d+1)*Ts-(tau(qq)-tau(pp));
    ix = d+1+(N+1)*mm;
    F(ix) = F(ix)+conj(H(pp))*H(qq)*theta.*exp(1i*pi*fc*theta).*sinc(fc*theta);
  end
end

Best Answer

Related Solutions

MATLAB: Frequency Selective Channel Coefficients in MATLAB

MATLAB: How to do this more efficiently

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