Agilent Technologies 93000 SOC Series Training Manual page 277

Lesson 7 – Executing the DAC Distortion Test
Total Harmonic Distortion
The total harmonic distortion (THD) compares the combined
power of the first N harmonics with the power of the input signal.
The THD is calculated as the ratio of the rms sum of the first N
harmonic components (typically up to the 5th harmonic) to the
rms value of a full-scale input signal.
THD is expressed in dB.
Calculation of THD
Signal-to-Noise Ratio
Signal-to-noise ratio (SNR) is calculated as the ratio of the rms
value of the input signal to the rms sum of all other spectral
components below the Nyquist frequency, excluding harmonics and
DC.
Calculation of SNR
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