Aliasing of a Signal

Question

I am really confused about this exam question regarding Aliasing.

I have a signal of 2Hz, which I needed to draw a square wave of, over a period of 8 seconds. It Then asks,

"Starting from the square wave you plotted above, plot the resulting wave if it is sampled at a rate of 0.5Hz. What is the phenomenon occurring here."

My Question is, what is the Aliased frequency?

What are the sample values that you get when you sample at 0.5 Hz? — Matt L., May 16 '15 at 08:12
That's where im confused..... For a 2Hz freq at least a 4Hz SR should be ideal. But now he told us that SR = 0.5Hz, so I'm wondering what the aliased frequency would be. — malteser, May 16 '15 at 08:24
Just draw the signal and take samples at 0.5 Hz and see what the corresponding values are, it's that simple! — Matt L., May 16 '15 at 08:26

score 2 · Accepted Answer · answered May 16 '15 at 08:29

2

HINT:

If you draw the signal and you take samples at a rate of $0.5\,\text{Hz}$, what are the sampled values that you get? Are they all different? If not, what is the frequency of a constant signal?

answered May 16 '15 at 08:29

Matt L.

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So, when you say I should take a sample every 0.5Hz, does that mean I should take a sample every 2 seconds (using t = 1/f)? Wouldnt that give a value of 0hz? – malteser May 16 '15 at 09:03
@melki0795: That's right. – Matt L. May 16 '15 at 09:09

Aliasing of a Signal

1 Answers1