How do Anti-Aliasing Filters filter the signal?

An anti-aliasing filter is just a low pass filter with the cutoff frequency (i.e., the -3 dB frequency) set to the Nyquist frequency. This filter cuts out any higher order frequency content in the input signal as any frequencies higher than the Nyquist frequency would be aliased.

1. How does anti-aliasing filter work?
2. How would you filter the signal to prevent aliasing?
3. Why do we use anti-aliasing filters?
4. How does aliasing affect a signal?

How does anti-aliasing filter work?

An anti-aliasing filter looks at the user-specified sampling frequency and removes any under-sampled frequencies that may appear in the signal (i.e. signal component frequencies >0.5 of the sampling frequency). PowerLabs with Anti-Aliasing filter include the PowerLab 15T, 26T, 2/26, 4/26 and later.

How would you filter the signal to prevent aliasing?

The solution to prevent aliasing is to band limit the input signals—limiting all input signal components below one half of the analog to digital converter's (ADC's) sampling frequency. Band limiting is accomplished by using analog low-pass filters that are called anti-aliasing filters.

Why do we use anti-aliasing filters?

This filter is an anti-alias filter because by attenuating the higher frequencies (greater than the Nyquist frequency), it prevents the aliasing components from being sampled. Because at this stage (before the sampler and the ADC) you are still in the analog world, the anti-aliasing filter is an analog filter.

How does aliasing affect a signal?

In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable (or aliases of one another) when sampled.