Downsample resample vs antialias fitlering + decimation

1. What is the difference between decimation and downsampling?
2. What is the need for anti-aliasing filter prior to downsampling?
3. Does downsampling cause aliasing?

What is the difference between decimation and downsampling?

Loosely speaking, “decimation” is the process of reducing the sampling rate. In practice, this usually implies lowpass-filtering a signal, then throwing away some of its samples. “Downsampling” is a more specific term which refers to just the process of throwing away samples, without the lowpass filtering operation.

What is the need for anti-aliasing filter prior to downsampling?

Expert-Verified Answer. 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.

Does downsampling cause aliasing?

If a discrete-time signal's baseband spectral support is not limited to an interval of width 2 π / M radians, downsampling by M results in aliasing. Aliasing is the distortion that occurs when overlapping copies of the signal's spectrum are added together.