Question on digital signal processing

[mngeow]

Ok so I have a set of digital signal processing questions where I'm not too sure about some of them.

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For the first question I'm not sure about parts (c) and (d),especially part (d) as I don't know what an ADC does to the frequency spectrum

For the 2nd question I do not know how to do that question at all.

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I'm also having alot of problems with these questions,I'm not sure how to draw the frequency spectrum if there is phase shift.

Thanks in advace

 

[crutschow]

So what do you understand about the relationship between the sample frequency and the frequency of the signal being sampled? I assume you should have some knowledge of that and the Nyquist theorem sample limit. If not you need to learn about that before we spoon feed you the answers.

 

[mngeow]

Mininum sampling frequency must be 2 times the signal frequency,after the signal is sampled,the frequency spectrum of the signal is repeated at each interval of the sampling frequency.I'm not sure about how to get the magnitudes of the various frequency spectrums and how to sketch the frequency spectrum after the signal has been passed through the ADC.

 

[crutschow]

Mininum sampling frequency must be 2 times the signal frequency,after the signal is sampled,the frequency spectrum of the signal is repeated at each interval of the sampling frequency.I'm not sure about how to get the magnitudes of the various frequency spectrums and how to sketch the frequency spectrum after the signal has been passed through the ADC.

OK. You understand the fundamentals.

The magnitude of the various frequency spectrums will be proportional to the input signal amplitudes x(t).

It's not completely clear to me what is meant by the spectrum after it passes through the ADC. If you look at the magnitude of the digital word samples from the A/D as they are output, then the spectrum should be the same as the output of the sample & hold.

 

[mngeow]

So for example in the 2nd picture,the frequency spectrum and B and C will be the same?