Homework Help: Non-uniformly sampled transfer function data

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1. Jan 22, 2016

bot19

I have non-uniformly sampled transfer function data (magnitude only) in the range of 100kHz and 200MHz. Using this transfer function, I would like to calculate output from specific input.

Question :

1. To obtain phase of the transfer function from the magnitude data, I am trying to use Hilbert transform.

(1) Phase = - imag( Hilbert( log ( TF_magnitude ) ) );

Is above line of code right? I found the below equation for calculating the minimum phase.

(2) θ(ω)=−H[ln(G(ω))]

I do not know why (1) use imag function.

2. I do not have the transfer function data under 100kHz, especially 0Hz. In this case, should I extrapolate the data under 100kHz? or insert 0? insert mean value? Does this make a big difference in output?

3. The sampling period of the transfer function is not linear, but uniform in log-scale. To make this linear, I tried to interpolate this using cubic-spline. But as the figure below, the transfer function does not have any regularity.

Therefore, I am trying to extract input data that is corresponding to transfer function data, calculate the output, and then interpolate the output for linear spaced output points. Does it matter if I work this way?​

In addition, should I make the output (or the transfer function) linear to perform IFFT in MATLAB?​

As I am poor at English, I am not sure my thoughts are conveyed.. but I hope so. Any help would be appreciate.

2. Jan 27, 2016

Staff: Admin

Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?

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