Dear all, This is a query from DSP which I need to implement in MATLAB. I am new to both, DSP and MATLAB. I have gone through the Transfer Function (TF) theory in MATLAB Help but could not really figure out how I use it for my application. Just to give you an idea of my task: I have two signals in time (output varying continuously with time hence I suppose they are time varying) from two measuring systems. I have to take the TF using one as the output and the other as the input. The intension is to see how the system is reacting to frequency and around what frequency the gain drops. From the TF theory, I should get the Laplace transform of the two signals and then take the ratio of o/p against i/p. But I am not sure if, 1) The two signals are time varying, can I take the Laplace? 2) If I can not take the Laplace, how do I get the TF? 3) If I can take the TF how do I get it in MATLAB? This could be an ill defined query so if there is anything not clear please let me know. I will try and clear it further. Your valuable inputs will be highly appreciated. Thanking you in anticipation.