There is some information in: Sampling theorem and Dirac comb, but I am wondering, how to apply this in practice.

There is some information in: Sampling theorem and Dirac comb, but I am wondering, how to apply this in practice.

would be nice, if someone could help me with following question:

How does a spectrum of a sampled signal locks like, if one use a zero-order-hold?

Starting with a analytic spectrum I generated a time signal and recalculated the spectrum and it fits quite well. In a next step I used a moving average for the time signal and again calculated the spectrum. The moving average filter can be considered as a convolution with a rectangular window. For the Fouier Transform this is simply a multiplication and finally the analytical spectrum can be found by multiplying the original spectrum with the sinc function and its conjugate. The spectrum based on the data again fits quite well to the analytical spectrum.

What does the spectrum of a sampled signal look like if one uses a zero-order-hold?

Starting with an analytic spectrum I generated a time signal and recalculated the spectrum and it fits quite well. In a next step I used a moving average for the time signal and again calculated the spectrum. The moving average filter can be considered as a convolution with a rectangular window. For the Fouier Transform this is simply a multiplication and finally the analytical spectrum can be found by multiplying the original spectrum with the sinc function and its conjugate. The spectrum based on the data again fits quite well to the analytical spectrum.