# Lecture 9 Blog, ECE438 Fall 2014, Prof. Boutin

Monday September 15, 2013 (Week 4) - See Course Outline.

Jump to Lecture 1, 2, 3 ,4 ,5 ,6 ,7 ,8 ,**9** ,10 ,11 ,12 ,13 ,14 ,15 ,16 ,17 ,18 ,19 ,20 ,21 ,22 ,23 ,24 ,25 ,26 ,27 ,28 ,29 ,30 ,31 ,32 ,33 ,34 ,35 ,36 ,37 ,38 ,39 ,40 ,41 ,42 ,43 ,44

Today we finished showing that the band-limited reconstruction formula we saw last time always coincides with the samples (even if the sampling frequency does not satisfy the Nyquist condition). We then looked at another type of reconstruction, namely a zero-order hold. After looking at this reconstruction in the frequency domain, we noted that it is not band-limited. We then moved on to the topic of finding the relationship between the CTFT of a signal x(t) and the DTFT of a sampling y[n]=x(nT). We showed that the DTFT of the sampling is simply a rescaled version of the CTFT of a comb of the signal. PLEASE MAKE SURE TO REMEMBER THIS RELATIONSHIP.

## Action Items

- Begin working on the third homework. It's due Monday.
- Work on your slecture.

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