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Analog Anti-Aliasing Filter

This example shows an analog implementation of an anti-aliasing filter for use with an A-to-D converter. The filter cut-off frequency is set to 500Hz in order to match the A-to-D converter sampling frequency of 1kHz. The test signal incorporates a desired 50Hz sinusoid plus a higher frequency component at 1100Hz that cannot be captured with a 1kHz A-to-D sampling frequency. The scope shows the captured signal without and with anti-aliasing. With the anti-alias filter the 50Hz sine wave amplitude is correctly measured with an amplitude of 1 and corresponding power of 0.5W, i.e., 27dBm for a 1ohm reference load.

Model

Simulation Results from Simscape Logging

The plot below shows the input and output voltages of the anti-aliasing filter.

Simulation Results from Spectrum Analyzer

With the anti-alias filter the 50Hz sine wave amplitude is correctly measured with an amplitude of 1 and corresponding power of 0.5W, i.e., 27dBm for a 1ohm reference load.