Hello All, I am trying to learn about lti systems and what not for my research work but before I can apply my research I have to understand the fundamentals, which is what this question is kind of about! I want to find h(t), the impulse response of an LTI system where my input and output are sinusoids. So I have made two functions. Input(t)=4*SIN(3*t+PI/8)+9*SIN(4*t-PI()/6) Output(t)=2*SIN(8*t+PI/3)+5*SIN(2*t-PI()/7) I did use matlab's fast fourier transform to bring results of n^10 data points to the frequency domain. I then do output(w)/input(w) ,output and input in frequency domain, to get H(w), the frequency response. I then use matlab to apply the inverse fast fourier transform to H(w) to obtain h(t). I use matlabs convolution function which should result in I(t)*h(t)=o(t) The problem is that this is not matching up. Am i doing something wrong with my thought process? Thanks!