It is also defined as a measure used to specify analog-to-digital and digital-to-analog converters (ADCs and DACs, respectively) and radio receivers.
SFDR is defined as the ratio of the RMS value of the carrier wave (maximum signal component) at the input of the ADC or output of DAC to the RMS value of the next largest noise or harmonic distortion component (which is referred to as “spurious” or a “spur”) at its output.
[1] In case of a radio receiver application, the definition is slightly different.
The reference is the minimum detectable signal level at the input of a receiver, which can be calculated through a knowledge of the noise figure and the input signal bandwidth of the receiver or the system.
The difference between this value and the input level which will produce distortion products equal to the minimum detectable signal referred to the input of the system is the SFDR of the system.