The following Convolve expression doesn't produce a result.

a = 0.1;
ImpulseResponse[t_] := 
  (1/(2.*Pi*10.*Sqrt[1 - a*a]))*Exp[-a*2*Pi*10*t]*Sin[2.*Pi*10.*Sqrt[1 - a*a]*t]
pulse[x_] := Cos[2*Pi*x]
Convolve[ImpulseResponse[t], pulse[t], t, x]

I am trying to figure out why and make it work, but I am not really successful at that.


closed as off-topic by corey979, m_goldberg, MarcoB, J. M. is away Dec 16 '16 at 2:19

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – corey979, m_goldberg, MarcoB, J. M. is away
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    $\begingroup$ My guess is because your impulse response is an exponential that goes to infinity as t goes to negative infinity. Notice in the docs that Convolve executes an integral from -infinity to infinity. You probably want to multiply the impulse response you've given by HeavisideTheta[t]. $\endgroup$ – N.J.Evans Dec 15 '16 at 20:31
  • $\begingroup$ @N.J.Evans You are absolutely right. `HeavisideTheta[t]´ does the job. $\endgroup$ – skrat Dec 15 '16 at 22:20

Your impulse response function isn't defined over {-∞, ∞}. But if you extend it as required with UnitStep, you will get a result.

With[{a = 1/10},
  impulseResponse[t_] := 
    (1/(2*Pi*10*Sqrt[1 - a*a]))*Exp[-a*2*Pi*10*t]*Sin[2*Pi*10*Sqrt[1 - a*a]*t] *
pulse[t_] := Cos[2*Pi*t]
Convolve[impulseResponse[t], pulse[t], t, x]

(3*Sqrt[11]*(99*Cos[2*Pi*x] + 2*Sin[2*Pi*x]))/(19610*Pi)


Not the answer you're looking for? Browse other questions tagged or ask your own question.