4 Replies Latest reply: Jan 19, 2004 12:00 AM by purple-disabled

# Compute DTFT of discrete time signal.

I need help in solving the DTFT of the following signal: x[n]=(0.5)^n cos 4n u[n]. I attached the problem. I have never used Mathcad for discrete solutions. Any help will be greatly appreciated. Thank you.

Eric
• ###### Compute DTFT of discrete time signal.
What is u(n)?

Richard
• ###### Compute DTFT of discrete time signal.
Here's a solution, but it still takes some manual work to get to the right place.

Lou
• ###### Compute DTFT of discrete time signal.
Neat. I hadn't a clue as to what u(n) was supposed to be, and wasn't sure what the discrete Fourier transform of an infinite sequence was supposed to be.

Mathcad's convert keyword can get the result simplified quite a bit. And, FWIW, Mathcad can work with the direct definition of the transform. Except that that Φ(n) (u(n)) has to be manually removed and used to control the summation range.

Tom Gutman
• ###### Compute DTFT of discrete time signal.
Thank you for the fast and accurate assistance with this DTFT problem.

Eric