Hello,
In the article, the author stated that:
" ...
That mysterious block labeled 'Zero-Order Hold' is merely the operation where
each u(k) input sample is repeated L–1 times. For example, if L = 3 and the
input to the Zero-Order Hold operation is {1,-4,3}, the output of the process
is {1,1,1,-4,-4,-4,3,3,3}."

Shouldn't the content of the resulting array be {1, 1, -4, -4, 3, 3}, i.e. repeat every member twice?
Sorry for my ignorance.

Regards

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