Signal-to-noise and distortion ratio (SINAD) is a measure of the quality of a signal from a communications device, often defined as

${\displaystyle \mathrm {SINAD} ={\frac {P_{\text{signal}}+P_{\text{noise}}+P_{\text{distortion}}}{P_{\text{noise}}+P_{\text{distortion}}}},}$

where ${\displaystyle P}$ is the average power of the signal, noise and distortion components. SINAD is usually expressed in dB and is quoted alongside the receiver RF sensitivity, to give a quantitative evaluation of the receiver sensitivity. Note that with this definition, unlike SNR, a SINAD reading can never be less than 1 (i.e. it is always positive when quoted in dB).

When calculating the distortion, it is common to exclude the DC components.[1]

1. The ratio of (a) total received power, i.e., the signal to (b) the noise-plus-distortion power. This is modeled by the equation above.[citation needed]
2. The ratio of (a) the power of a test signal, i.e. a sine wave, to (b) the residual received power, i.e. noise-plus-distortion power. With this definition, it is possible to have a SINAD level less than one. This definition is used in the calculation of ENOB for DACs[2] and ADCs.[3]

Information on the relations between SINAD, ENOB, SNR, THD and SFDR can be found in.[4]

## Contents

A typical example, quoted from a commercial hand held VHF or UHF radio, might be: