I have two sensors that have a cross talk between them. I would like to cancel the cross talk. For this I recorded two tracks, where sensor no.1 (called x1) has some input, and sensor no.2 (called x2) is zero.
I was told to make the following operations:
Since your cross talk is small:
1) Simply measure the transfer function $H_{ba}(\omega)$ directly.
2) Subtract it out as follows:
2.1) Measure the transfer function from signal A to sensor B when signal B is 0.
2.2) Create a filter from this transfer function (FIR or IIR, depending on it's shape).
2.3) Now you can measure and subtract a filtered version from sensor signal A from sensor signal B:
$y_b'(t) = y_b(t)-h_{ab}(t)*y_a(t)$. Where $h_{ab}(t)$ is the impulse response of your cross talk filter and $*$ the convolution operator.
Here is a Matlab code that I wrote for this purpose, but its performance is really bad. If someone has a suggestion what I did wrong, or can suggest a new code I will be grateful. If I may say, a friend helped me to implement this, and I think that we did not implement the filter part, but maybe I am wrong.
% The files designated to measure the transfer function.
% x1 has some input. x2 is is zero, and affected by the x1.
x1 = wavread(file1);
x2 = wavread(file2);
%The transfer function.
Hab = fft(x2)./fft(x1);
hab=ifft(Hab);
% Some new tracks, where x3 is recorded from sensor no.1 and x4 from sensor no.2.
% All the files have the same length.
x3 = wavread(file3);
x4 = wavread(file4);
c=conv(hab,x3);
% Subtracted signal
x4 = x4 - c(1:length(x4));
The following code did not subtract the cross talk on x4.
Here are some images explaining the problem. For some frequencies the above code actually did a good job and subtracted the cross talk, and for some it did the opposite and increased the energy. plot(abs(fft(x4))):
Good - Frequency energy subtracted:
Bad - Frequency energy increased (!):
Thank you!
