In the context of sampling, what is the purpose of an anti-aliasing filter?

In the context of sampling, what is the purpose of an anti-aliasing filter?

• A. To increase the sampling rate.
• B. To remove DC component.
• C. To convert analog to digital.
• D. To limit the signal bandwidth before sampling to avoid aliasing.

Answer: (D)

Anti-aliasing filtering is used to prevent aliasing when sampling a continuous-time signal. By placing a low-pass filter before the analog-to-digital converter, high-frequency components are attenuated so that the signal’s bandwidth stays below half the sampling rate (the Nyquist limit). If those higher frequencies aren’t suppressed, they fold back into the lower frequencies during sampling, distorting the digital representation. Limiting the bandwidth before sampling guarantees that the sampled signal accurately reflects the original spectrum. The other statements don’t fit this purpose: simply increasing the sampling rate changes the Nyquist limit but doesn’t condition the signal to avoid aliasing; removing a DC component isn’t about aliasing; and the conversion to digital involves sampling and quantization, with the anti-aliasing filter serving only to condition the signal prior to sampling.

Anti-aliasing filtering is used to prevent aliasing when sampling a continuous-time signal. By placing a low-pass filter before the analog-to-digital converter, high-frequency components are attenuated so that the signal’s bandwidth stays below half the sampling rate (the Nyquist limit). If those higher frequencies aren’t suppressed, they fold back into the lower frequencies during sampling, distorting the digital representation. Limiting the bandwidth before sampling guarantees that the sampled signal accurately reflects the original spectrum.

The other statements don’t fit this purpose: simply increasing the sampling rate changes the Nyquist limit but doesn’t condition the signal to avoid aliasing; removing a DC component isn’t about aliasing; and the conversion to digital involves sampling and quantization, with the anti-aliasing filter serving only to condition the signal prior to sampling.