Aliasing is due to undersampling and its effects are attenuation and non uniform spectral gain.

In the method of natural sampling, the top of each pulse in the sampled sequence retains the same shape of the analog input signal.

Oversampling is most economic way of sampling or for converting analog information to digital as performing signal processing using digital system is less costlier than doing it with high performace analog system.

The analog data is converted to digital data through sampling. Sampling is done using sample and hold mechanism which uses transistor, capacitor or shutter etc.

When we perform fourier tranform on one impulse train we will get another impulse train with its period reciprocally related to each other.

In sampling process, input data is split up into samples whose output samples are called as pulse amplitude modulation as the amplitude of the samples is derived from the input waveform.

In impulse sampling the input signal is multiplied with impulse train and in natural sampling it is multiplied with pulse train.

Aliasing can be removed using both prefiltering and postfiltering but prefiltering is most effective and preferred.

By sampling theorem the input can be derived from the output samples if Ts is lesser than or equal to 1/2fm.

In flat top sampling the top of the pulses are flat which in turn means that they have the same amplitude.