ADC Alias Calculator

When an analog-to-digital converter (ADC) samples a signal faster than twice its frequency, the signal is captured cleanly — but when it doesn't, a distorted copy called an alias appears at a different frequency. Enter your Sampling Frequency (fs), Signal Frequency (fin), Maximum Analysis Frequency, and Maximum Harmonic Order into the ADC Alias Calculator to see the Nyquist Frequency, Aliased Frequency, Nyquist Zone, and Aliasing Status for your signal and its harmonics.

Hz

ADC sampling frequency

Hz

Input signal frequency to analyze

Hz

Upper limit for harmonic analysis

Results

Nyquist Frequency

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Aliased Frequency

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Nyquist Zone

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Aliasing Status

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Results Table

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Frequently Asked Questions

What is ADC aliasing and why does it occur?

ADC aliasing occurs when the sampling frequency is insufficient to accurately represent high-frequency signal components. According to the Nyquist theorem, the sampling rate must be at least twice the highest frequency component to avoid aliasing.

How do I calculate the Nyquist frequency?

The Nyquist frequency is calculated as half the sampling frequency (fNyq = fs/2). It represents the highest frequency that can be accurately sampled without aliasing.

What are Nyquist zones and how do they affect aliasing?

Nyquist zones are frequency bands of width equal to the Nyquist frequency. Signals in odd-numbered zones (1st, 3rd, 5th) alias normally, while signals in even-numbered zones (2nd, 4th, 6th) alias with frequency inversion.

How do harmonics contribute to ADC aliasing?

Even if the fundamental frequency is below the Nyquist limit, its harmonics may exceed it and fold back into the frequency band of interest, creating spurious signals that can interfere with the desired signal.

What is the difference between oversampling and undersampling?

Oversampling occurs when fs > 2 × signal frequency, providing good signal reproduction. Undersampling occurs when fs < 2 × signal frequency, deliberately used in some applications but requiring careful alias management.

How can I prevent aliasing in my ADC system?

Use anti-aliasing filters to remove frequency components above the Nyquist frequency before sampling, increase the sampling rate, or design the system to tolerate controlled aliasing in undersampling applications.

What does it mean when a signal folds back into the first Nyquist zone?

When a high-frequency signal or harmonic aliases into the first Nyquist zone (0 to fNyq), it appears as a lower-frequency spurious signal that can interfere with your desired signal band.