Why is an LPF required before the sampler?

Why is an LPF required before the sampler?

In general before doing sampling, we add low pass filter in order to avoid aliasing effect.

What is the need for anti-aliasing filter?

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.

Why the LP filter is used prior to down sampler in decimator?

Specifically, the signal’s highest frequency must be less than half the post-decimation sampling rate. However, since the original signal has components up to 10 kHz, you must lowpass-filter the signal prior to downsampling to remove all components above 5 kHz so that no aliasing will occur when downsampling.

What is the cut-off frequency of the ideal anti-aliasing filter?

The anti-aliasing would have a cut-off frequency of 20 KHz, but since this is not an ideal filter usually the sampling frequency used goes from 44.1 KHz to 96 KHz, allowing a transition band of at least 2 KHz.

How does downsampling reduce high frequency signal components?

Reduce high-frequency signal components with a digital lowpass filter. Decimate the filtered signal by M; that is, keep only every Mth sample. Step 2 alone allows high-frequency signal components to be misinterpreted by subsequent users of the data, which is a form of distortion called aliasing.

What happens if you downsample a signal to 512hz?

If it was downsampled to 512Hz then the frequency content would now be reduced to 256Hz, due to the Nyquist theory. However, if there were frequencies present in the original signal between 256 and 512Hz they would be subject to aliasing and would cause incorrect frequencies to be displayed in the frequency domain.

When to upsample and when to downsample a signal?

So, in order to downsample the signal we must first low pass filter the data to remove the content between 256Hz and 512Hz before it can be resampled. The purpose of upsampling is to add samples to a signal, whilst maintaining its length with respect to time.

What happens when you decimate the filtered signal by M?

Decimate the filtered signal by M; that is, keep only every Mth sample. Step 2 alone allows high-frequency signal components to be misinterpreted by subsequent users of the data, which is a form of distortion called aliasing. Step 1, when necessary, suppresses aliasing to an acceptable level.