Question

What is need of antialiasing filter prior to downsampling and anti-imaging filter after up sampling a signal?

Answer 1

An "anti - aliasing" or "anti-imaging" channel / filter is set before the A-to-D converter, to counteract / prevent flag frequencies more noteworthy than a large portion of the testing rate from being digitized, which would create pictures at undesirable frequencies.

It's legitimately called a "reconstruction channel" and it is really a vital piece of Digital-to-Analog procedure. It pursues the D-to-A converter. Individuals who don't comprehend the procedure commonly make contentions about the "staircase" idea of the recreated signal, however they are "cheating" by glimpsing inside the procedure as opposed to at its real yield (after that filter).