Amateur ExtraE7F09
Why is an anti-aliasing filter required in a decimator?
A
Answer
Practical circuits and system design
Type
A
It removes high-frequency signal components that would otherwise be reproduced as lower frequency components
B
It peaks the response of the decimator, improving bandwidth
C
It removes low-frequency signal components to eliminate the need for DC restoration
D
It notches out the sampling frequency to avoid sampling errors
Answer Notes
When decimation reduces the sample rate of a digital signal, the Nyquist frequency (which is always half the sample rate) also inherently decreases. If the original digital signal contains frequencies higher than this newly reduced Nyquist limit, those high frequencies will "fold back" or alias into the lower frequency band, causing severe digital distortion.
To prevent this distortion, a digital low-pass filter known as an anti-aliasing filter is applied right before the samples are removed. This ensures that any signal components above the new Nyquist limit are completely eliminated and cannot become unwanted low-frequency aliases.
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What is the function of decimation?
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What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a direct-sampling software defined radio (SDR)?