I have been reading Signals and Systems (2nd ed.) recently. Chapter 7 is about sampling. Oppenheim uses discrete-time signals and continuous-time signals to explain sampling.
- But why do we need discrete-time signals? We use the A/D to receive and convert the continuous-time signal, so the signal is already discrete. In other words, the discrete signals are the sampled version of continuous signals.
- Is there any practical meaning to sample discrete-time signals?