Feedback for Group Assignment 2.3¶

CEGM1000 MUDE: Week 2.3, Friday, Nov 29, 2024.

General feedback to the students¶

Overall good work was delivered on GA 2.3, resulting in good scores! There are only a few details to comment on.

Question 2

Quite a lot of groups concluded with Task 2 that, next to a peak at a frequency of 1 Hz, there was a peak at a frequency of 100 Hz. Of course, this may not be very easy to read directly from the plot (with log-scale), though there is no reason for a peak at 100 Hz at all. Instead this peak is at 99 Hz, which equals the 100 Hz sampling frequency minus the 1 Hz (input sine wave); this is actually already the left-side part of the first copy of the spectrum (due to sampling the signal).

Question 5

With Task 5, many groups responded to the required equation for the alias-frequency with the Nyquist rate (fs >= 2*fh). A simple mathematical equation for the sampling frequency, the input-wave frequency and the resulting alias frequeny is: f_alias = f_s – f_wave (and this expression can be enhanced for multiples of the sampling frequency and larger differences between f_s and f_wave). As a courtesy, also the first answer (with the Nyquist rate) was awarded.

log-scale

And finally, correctly reading numerical values from a log-scale plot sometimes turned out to be a challenge.

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