Amplitude Spectrum of a function

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aliza mustafa
aliza mustafa on 18 Sep 2022
Answered: Chunru on 19 Sep 2022
Hi,
My question is related to plotting amplitude spectrum.
Problem 1: (I have solved it) I have to represent the following function as a discrete set of N=100 numbers separated by time increment of 1/N:
e(t) = 3sin2.1t + 2sin1.9t
I did it using stem function and plotted it.
Problem 2: (I have question about it) The next thing was to repeat the same above all, using dataset of 200 points with time increment of 1/N and 1/2N.
My question is a bit basic but I just want to clear if I am following the right path to solve my problem.
I want to ask that for problem 2, for both 1/N and 1/2N, should I use N=200 (as I believe it is separate problem)?
A few of my mates has suggsted to use N=100 for 1/N and N=200 for 1/2N.
which one is right thing?
Any help will be highly appreciated. Thanks
  1 Comment
dpb
dpb on 18 Sep 2022
We can't answer that as posed; it is totally dependent upon how the question itself was written; a paraphrase of what it says isn't the same thing...it may well have been ambiguous as written; would seem the logical thing to do would to get the instructor to clarify (or just solve the problem with both interpretations and explain why).

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Answers (1)

Chunru
Chunru on 19 Sep 2022
If you are studying the effect of sampling frequency, you may want to fix the signal duration, for example .
In this case, you have:
  • fs = N; t = 0:1/fs:1; which equivelant to t=0:1/N:1, (whether N=100 or 200)

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