Question

Can aliasing be prevented? If so, give one example of how.

Answer 1

Aliasing normally occurs when a digital signal is processed.As we know the first step of digital signal processing is sampling.The incoming continous signal is sampled based on certain conditions to make it discrete signals.These conditions are called Niquist conditions and the theory is Niquist shannon theory.Niquist sampling rate is the lowest sampling rate that can be used without having aliasing.The theory states that the sampling frequency should be equal to or greater than twice the maximum frequency of the continous time signal.

That is Fs=2Fm

If this condition is satisfied we can make a represent a continous signal in the form of discrete signal.Also we can recover back the original signal whenever needed.

If this condition is not met under sampling occurs and aliasing occurs as the result of undersampling.Aliasing means overlap of signals occurs and we can't sample the signal or recover it from the samples.So inorder to avoid that we have follow the Niquist rate, that is Fs should be greater than Fm.Another method is to use anti aliasing filters.They are low pass filters and they can attenuate the unnecessary high frequency components of a signal.