As long as your sampling rate is high enough (more than double the signal frequency), you can always detect the signal with high accuracy quantization becomes more accurate as long as you do not increase the noise level. The relationship between accuracy in the detected signal and the sampling rate is shown in the image below. This particular sampling frequency at which the system can prevent aliasing is called the Nyquist frequency. In the case when aliasing occurs, the ADC will output a series of digital pulses that quantifies a signal with frequency equal to the difference between the sampling rate and the center frequency. In other words, if the signal’s center frequency is more than half the sampling frequency, then aliasing will occur, and the ADC will detect a low alias frequency signal in error, rather than detecting the desired center frequency of the input high frequency signal. When sampling an analog signal with a specific center frequency, aliasing will occur if the sampling frequency is less than double the center frequency. In this way, the goal in anti-aliasing filter design is to set the filter’s -3 dB cutoff frequency equal to half the sampling frequency. Any anti-aliasing filter design intends to remove high frequency content from the signal you want to sample with the goal of preventing aliasing. In theory, any type of active low-pass filter with unity gain can be used as an anti-aliasing filter. Anti-aliasing Filter Design PointsĪn anti-aliasing filter is effectively a low-pass filter that is placed on the input of an analog-digital converter (ADC). This problem can be overcome in a few ways, depending on the harmonic content of your analog signal and the speed of your system.

This happens when the sampling period is equal to the oscillation period, and the sampling device will only reliably measure a fixed signal.

When aliasing occurs, the signal you’re trying to sample appears to have a constant level, i.e., you cannot observe an oscillation. I later learned about sampling rates with digital systems and how this leads to a phenomenon called aliasing. When I was younger, I racked my brain trying to figure out how this was possible and why viewing the wheels on camera made a difference. Whenever I watched car commercials where the camera pans along the driving vehicle, there was always one particular speed where the spokes in the wheels appeared to remain stationary or even move backwards. Aliasing is a well-known phenomenon in digital photography, but it also arises in analog-to-digital conversion.

Digital filter designer