Can you check what I did wrong here? (code for finding attenuation value and delay using filter)

 x = zeros(1,100);
x(1:10) = 1;
x(50:59) = 0.5;
%function x
alph = 0.01:0.01:1;%attenuation value
Td = 1:100;%delay
N=3;
for i = 1:length(alph)
    a = alph(i);
    for j = 1:length(Td)
        td = Td(j);
        for k = 0:N;
            filter(k*td+1) = (-a)^k; %filter
        end
        y = conv(x,filter);
        E(i,j) = sum(y.^2); 
    end
end

Hello!

I'm working on filtering echo using Matlab.

so here's code for simple function with delay:49, attenuation:0.5

This is the code for finding appropriate delay and attenuation values assuming we do not know them.

The assignment I'm working on tells me to find the correct values by calculating energy (y(t)^2) for each values of alph and Td.

Out of those energy, minimum value would be the correct delay and attenuation. when I perform this code in matlab, the energy goes up really large which should not be.

I have no idea what I did wrong. and also, how do i find the matrix's position of minimum value?

and equation for the filter I used is: h(t)=sigma (k=0 to N)[(-a)^k Dirac(t-k*td)]

Thanks