Band-limited signal recovery with finite bit depth

1. Can a band-limited signal ever be time limited?
2. Why are signals band-limited?
3. Why are signals band-limited before sampling with ADC?

Can a band-limited signal ever be time limited?

Consequently, for any time interval, cannot vanish everywhere in that interval, which implies that. Conversely, a signal that is of finite duration cannot be band-limited. In other words, a signal cannot be both time limited and band limited.

Why are signals band-limited?

A signal is called bandwidth – limited or simply band-limited when the amplitude of the spectrum goes to zero whenever its frequency crosses the allowable limits. Thus, its Fourier transform is non-zero only for a finite frequency interval. A band-limited signal is represented by a finite number of harmonics.

Why are signals band-limited before sampling with ADC?

"why band-limit a signal?" There will be components of a system that have bandwidth limitations. For example, ADCs have a limit as to how fast they can sample. Therefore the frequency content would need to be limited otherwise you would get aliased frequencies.