spuriousfree

Spuriousfree is an adjective used in electronics and signal processing to describe a signal, measurement, or system that contains no spurious components—unwanted frequency components that can arise from nonlinearity, mixing, clock feedthrough, leakage, or external interference—within a defined frequency range or under specified operating conditions.

In practice, spurious-free performance is most closely associated with spurious-free dynamic range (SFDR), a metric used for RF front ends, analog-to-digital converters, digital-to-analog converters, and receivers. SFDR characterizes how clean a signal is with respect to unwanted spectral content, aside from the fundamental tone.

SFDR is defined as the ratio, usually expressed in decibels relative to the carrier (dBc), between the amplitude of the fundamental tone and the amplitude of the strongest spur within a given bandwidth. A higher SFDR indicates a cleaner signal with less interference from spurious components. Commonly specified SFDR values are provided for a defined measurement bandwidth and reference tone.

Achieving spurious-free behavior involves improving linearity and isolation, including high-quality clocks, careful impedance matching, clean circuit layouts, effective filtering, shielding, and, where applicable, calibration or dithering techniques. Design practices aim to minimize nonlinearity, leakage, and crosstalk that generate spurs and harmonics.

In practice, the term is widely used in datasheets and marketing to indicate performance, but it is not a universal standard by itself. Measurement details—such as bandwidth, windowing, and which spurs are included—vary by application and specification.