About Signal to Noise Ratio
SNR is a measurement parameter that compares the level of the desired signal to the level of an undesired signal (noise). Noise means any unwanted disturbance that degrades the quality of the desired signal or Information. There are thermal Noise, electronic Noise and various other types. Temperature and humidity can also affect the noise levels. To detect the quality of a given signal, the signal-to-noise ratio term is used.
Often expressed in decibels, a ratio that is higher than 1: 1, or greater than 0 dB, indicates that the signal is more compared to noise.
Where P signal is the Power of a signal and Pnoise is the background noise.
The higher the ratio, the better the signal quality. The ratio can be zero, a positive number or a negative number. For example, a Wi-Fi signal with S/N of 60 dB will deliver better network services than a signal with S/N of 20 dB
If the noise level is higher than your desired signal, S/N is low- it can disrupt a wide range of data transfer, audio and video streams etc.
How do you calculate Signal -to -Noise Ratio?
It is calculated using logarithm base 10.
S/N = 20 log10(Ps/Pn)
Where Ps is the desired signal in microvolt and Pn is the noise signal in the microvolt
Also, if Ps and Pn are measured in watts, the S/N ratio is calculated by the following expression
S/N = 10 log10(Ps/Pn)
As an example, suppose that Ps equals 100 microvolts and Pn equals 1 microvolt.
S/N ratio = 20log100=40dB
A signal of 40dB means that it is very strong enough to be detectable.
On the other hand , if Ps equals 1 microvolt and Pn equals 100 microvolts, then
S/N ratio=20log(1/100)= -40dB
A negative S/N ratio means the signal is very weak and is not strong enough to be detectable.
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