Questions and Comments for

DTFT of a Cosine Sampled Above and Below the Nyquist Rate

A slecture by ECE student Sutton Hathorn



Please post your reviews, comments, and questions below.



  • Review by Yijun Han

The difference between CTFT and DTFT is clearly stated and the derivation for DTFT sampling at frequency above Nyquist rate is concise. It would be better if you provide more steps when computing DTFT sampling at frequency below Nyquist rate.


  • Review by Fabian Faes

I really liked the use of matlab plots to illustrate the DTFT sampling below and above the Nyquist rate. However I wish there was more steps in the actual calculations of these curves as I found it a bit hard to follow in that aspect. Other than that I find it a great slecture with the matlab content really aiding understanding a lot.


  • Review by Andrew Pawling

Great job with the graphs! The matlab plot show the signal and where it is being sampled at was a great illustration. The calculations for the frequency domain needs to be more detailed. Also you don't seem to indicate the magnitude scaling from the two different sampling rates.


  • Review by Sahil Sanghani

Great job! All the important points within the topic are emphasized and stated clearly. The graphs are good visuals as well. In the sampling above Nyquist section, the third line of the derivation has a small typo. Within the second delta, the 2000 isn't completely factored out. All in all this was a great slecture.


  • Review by Michael Hayashi

This is a marvelous slecture overall. I thought showing where the sample points lie on the original CT signal was a nice touch. The graphs aid the relationship between a DTFT of a sampling and the CTFT of the original signal, but I feel that the delta functions from the center copy need to be made more distinct from those from shifted copies to better show how the original signal could not be found by using a low-pass filter. The takeaways are good, but the spelling of "Shannon" should be checked.


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Basic linear algebra uncovers and clarifies very important geometry and algebra.

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