# Sampling frequencies

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1. Jan 27, 2015

### electronic engineer

1. The problem statement, all variables and given/known data

We have the following signal frequencies:

f1=18 Hz, f2=510 Hz, f3=1100 Hz

when using the sampling frequency fs=1000 Hz.

how would these signals be like?

my question is if I could use the same formula stated below for all the frequencies f1,f2,f3.. because the second and third ones are above the Nyquist Frequency fc=fs/2=500 Hz so there would be aliasing in this case.

and what about the graphs for these samplings?

2. Relevant equations

when using another sampling frequency fs=1002 Hz

and here also would be the same questions.

3. The attempt at a solution

I used the formula:

$$S_{\Delta }(v)= f_{s}\sum_{n=-\infty}^{+\infty}(S(v-n*f_{s}))$$

for the first frequency f1= 18 Hz I had:

$$S_{\Delta}(18)=1000\sum(S(18-n*1000))$$

where $$n=-\infty$$ to $$+\infty$$

2. Jan 27, 2015

### haruspex

Do you mean, for each actual frequency, what is the lowest frequency that could yield the same sampling results?

3. Jan 28, 2015

### electronic engineer

No i mean for each actual frequency wha are the sampling results for fs=1000 Hz and then for fs=1002 Hz.

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