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Is any digital signal comprised of one or more discrete signals?

i.e. one discrete signal or two or more discrete sub-signals?

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    $\begingroup$ Your question makes no sense to me. I think you're making some assuptions that you're not mentioning. Could you try clarifying in what sense a signal might be comprised of other signals? What do you mean by "digital" and by "discrete" -- is it in time or in amplitude? $\endgroup$
    – MBaz
    Mar 21, 2022 at 22:56
  • $\begingroup$ @MBaz I define digital signal as a signal which is discrete both time and amplitude. $\endgroup$
    – yaraklis
    Mar 22, 2022 at 3:20
  • $\begingroup$ @MBaz so yes I understand, if it's discrete only in time but not in amplitude it will be just "discrete signal" and not "digital signal" right? $\endgroup$
    – yaraklis
    Mar 22, 2022 at 4:36
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    $\begingroup$ I mean, you can always take a digital signal and split it into even and odd samples, both of which will also be discrete sub-signals... $\endgroup$ Mar 22, 2022 at 6:31

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Ok I now understand the question I believe, let me clarify the assumed definitions:

digital signal: discrete in time and discrete in magnitude.

discrete-time signal: discrete in time only, may or may not be discrete in magnitude.

Therefore, a digital signal is a discrete-time signal but the converse is not necessarily true.

As far as decompositions, we can express any digital signal or any discrete-time signal as one or more of the same kind of signal (just as we can express $5$ as being $3+2$). Given the conditions above, we see however that we cannot express any discrete-time signal as being a sum of one or digital signals since the discrete-time signals can have non-rational magnitudes while a digital signal cannot. (We can only approximate which leads to the whole theory of quantization noise).

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  • $\begingroup$ but the converse is not necessarily true I am sorry, I don't understand this. $\endgroup$
    – yaraklis
    Mar 22, 2022 at 9:21
  • $\begingroup$ Sorry- "The converse is not necessarily true" means if you reverse that statement, it may not always hold (See en.wikipedia.org/wiki/…) This means specifically that a signal that is discrete-time may or may not also be a digital signal. We can have discrete-time signals that are NOT "digital signals" when we define digital as being both discrete in time and discrete in magnitude. $\endgroup$ Mar 22, 2022 at 9:26

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