ADC Spurious Calculator

ADC spurious analysis identifies unwanted frequency components that appear in the digitized signal due to harmonic distortion and Nyquist aliasing. This is crucial for determining if harmonics of the input signal will fold back into your frequency band of interest, potentially corrupting your measurements.

When harmonics of the input signal exceed the Nyquist frequency (half the sampling rate), they fold back or 'alias' into lower frequency ranges. This can cause spurious signals to appear within your desired frequency band, degrading signal quality and measurement accuracy.

Higher sampling frequencies push harmonic aliases further away from the fundamental frequency, improving spurious performance. However, the optimal sampling rate depends on your specific application and the frequency band of interest.

The table shows each harmonic order, its original frequency, and where it aliases after sampling. Pay attention to harmonics marked as 'In Band' - these are the ones that will interfere with your signal of interest and may require filtering or different sampling strategies.

Spurious Free Dynamic Range (SFDR) is the ratio between the fundamental signal amplitude and the largest spurious signal amplitude, typically expressed in dB. Higher SFDR values indicate better ADC performance with fewer spurious components.

Use anti-aliasing filters before the ADC, choose appropriate sampling frequencies, ensure clean input signals with low harmonic content, and select ADCs with better linearity specifications. Proper board layout and power supply design also help minimize spurious signals.

Typically analyze harmonics up to the 9th order as higher-order harmonics have progressively lower amplitudes. However, for high-performance applications or when using ADCs with poor linearity, you may need to consider higher-order harmonics up to the 20th order.