Signal-to-noise and distortion ratio (SINAD) is a measure of the quality of a signal from a communications device, often defined as
:
where
is the average power of the
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
,
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
and
distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
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.
Due to widespread use, SINAD has collected several different definitions. SINAD is commonly defined as:
#The ratio of (a) total received
power
Power most often refers to:
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power
* Power (social and political), the ability to influence people or events
** Abusive power
Power may a ...
, i.e., the signal to (b) the noise-plus-distortion power. This is modeled by the equation above.
#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
Effective number of bits (ENOB) is a measure of the dynamic range of an analog-to-digital converter (ADC), digital-to-analog converter, or their associated circuitry. The resolution of an ADC is specified by the number of bits used to represent t ...
for
DACs and
ADCs.
Information on the relations between SINAD,
ENOB
Effective number of bits (ENOB) is a measure of the dynamic range of an analog-to-digital converter (ADC), digital-to-analog converter, or their associated circuitry. The resolution of an ADC is specified by the number of bits used to represent t ...
,
SNR,
THD and
SFDR can be found in.
Commercial radio specifications
A typical example, quoted from a commercial hand held
VHF or
UHF radio, might be:
:Receiver sensitivity: 0.25 μV at 12 dB SINAD.
This is stating that the receiver will produce intelligible speech with a signal at its input as low as 0.25 μV. Radio receiver designers will test the product in a laboratory using a procedure, which is typically as follows:
* With no signal present on the input, the noise and distortion of the receiver are measured at a convenient level.
* A signal is applied to the input such that the output increases by 12 dB.
* The level of the signal needed to produce this is noted. In this case, it was found to be 0.25 microvolts.
According to the radio designer, intelligible speech can be detected 12 dB above the receiver's noise floor (noise and distortion). Regardless of how accurate this output power is regarding intelligible speech, having a standard output SINAD allows easy comparison between radio receiver input sensitivities. This 0.25 μV value is typical for VHF commercial radio, while 0.35 μV is probably more typical for UHF. In the real world, lower SINAD values (more noise) can still result in intelligible speech, but it is tiresome work to listen to a voice in that much noise.
See also
*
Signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in deci ...
*
Total harmonic distortion
The total harmonic distortion (THD or THDi) is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Distortion facto ...
(THD+N)
References
External links
SINAD and SINAD measurements for radio receivers
{{FS1037C MS188
Noise (electronics)
Error measures