This lesson presents several examples of sampling to illustrate aliasing and the conditions of the sampling theorem.

## Prerequisites

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Kamiar Radnosrati says

Hi,

I\m wondering if answers to Quiz number 1 and 2 are correct or I'm doing something wrong. I get totally different results.

Barry Van Veen says

I just reworked the problems and obtained the answers given. Note that the sinusoid is complex (no negative frequency term) and the sampling interval is given, not the sampling frequency. Also, the answer is in discrete-time frequency units of rads while the sinusoid being sampled has frequency specified in Hertz. All of these factors need to be accounted for in arriving at the right answers.

Kamiar Radnosrati says

I considered them could you please correct me here. the complex sinusoid frequency is "2*pi" and the sampling frequency is "4*pi/3". Then we have aliasing here and for k=0, the first frequency is "2*pi" and for K=1 we will have "2*pi + 4*pi/3" and so on.

Barry Van Veen says

You are correct, but your calculations are in units of rads/sec, which I denote with . The question asks for discrete-time frequency in units of rads You convert using . So rads/sec becomes rads, or answer a). To get answer c) you use or .

sipan markanian says

I am trying to work out question 5, but I am not getting the same answer. I am getting w=0.6*pi + 2*k*pi. Where did I make an error?

Barry Van Veen says

You didn't make an error - I did. Thanks for catching that. I've corrected the problem.