All  Engineering and Technology Information in One Place.....


About This Site

Sections  Directory

Search This Site

Privacy Policy

Tired of looking for a job?, Cansado de buscar trabajo?





Semiconductors Devices


Electronics Technology Information Sites


Science and Tech Forum


Electronics Engineering Information by Categories


Engineering and Science Software


Free Science-Tek Magazines and Publications


Regulatory Offices and Agencies and Standards


Patents  Information


Prototypes Developing Houses, Devices and Tools


IC’s Foundries  and IC Development Services


Certification Labs


Operation Manuals


Physics Units Converter Calculators

Convert any type of unit into any other of any system or scale


Alternative Energies Tutorials:


Ocean Energy

Wind Energy

Solar Energy



Lean Manufacturing Tutorials:

The Seven Causes of Waste

The 5S

The 5 Whys

The 4 M’s +1

Cause Effect / Fish Diagram  

The 4W’s +H+W



Project Charter Example

Value Stream Mapping Introduction and Icons

Current or Present State Map

Future Sate Mapping

Cell Production

Kanban Production System




Electronics and Electromechanical Distributors


Jobs Portal

Easily find your dream Job


Technology News


Science News


Business News


Electronics, RF and Communication Concepts

Rsistors and capacitors colors code

The Logarithm

The bel, decibel , the dbm and the dbmv

Electrical noise definition and Thermal noise

Signal to noise ratio

Physical Constants


Electronic Warfare and Radar Systems Engineering Handbook

Search this site

Para nuestros amigos de habla hispana, los invitamos a visitar el portal tecnológico en español:



If you likes this site, please check like and share above:

To share this site:

To share this page:

If you don’t see the page information, remove the advertising above by clicking on the x on the upper right side of it

Signal to Noise Ratio S/N


Signal To Noise Ratio

When signals are detected, processed or amplified is essential to know the the signal integrity that could be affected by any undesirable signal or noise produced internally in the circuits or system or picked up externally, in order to measure the signal strength against the noise the concept of “signal to noise ratio” was established.

The signal to noise ratio is the ratio of a signal level versus a noise level, and it is normally expressed in decibels as it is illustrated below, the signal to noise ratio can be represented in the frequency or time domains.


                          Signal level =  60 dbm




                                                                                    Average noise level = 10 dbm              



The above picture represents the signal to noise ratio in the frequency domain as can be seen in a spectrum analyzer for a signal with a power of 60 dbm and average noise of 10 dbm. For most practical purposes the average noise level is considered, but for critical operation the noise pick levels provide a safer signal to noise ratio analysis specially for random high noise spikes.

A = Signal to noise level considering the picks of the noise  

B = Signal to noise level considering the average of the noise

From the picture the signal to noise ratio considering the average noise level is 50 dbs since the signal is 50 dbs above the noise level.

The minimum signal to noise ratio specifications will depend on the specific system requirements and application, while for most commercial application a signal to noise ratio of few dbs could be sufficient, for others systems could not, is the job of the engineer to verify the proper signal to noise requirement for the system, for example the S/N ratio for the reception of ananalog TV signal must be superior to 40 db to guaranty a noise free image.

When  the signal under consideration is a signal carrier then is called the carrier to noise ratio or C/N.









The above picture represents the signal to noise ratio as could be seen in a oscilloscope, since an oscilloscope normally do not display signal amplitudes in decibels, the S/N in decibels can be calculated by using the relationship:

20 Log10  (S/N)


What is the S/N ratio in decibels of a signal with an amplitude of  one volts and a noise amplitude of 50 millivolts?

S=1 V

N= .050 V

S/N in decibels = 20 Log10 (1/.050) = 26.02 decibels

Be aware that the wider the channel bandwidth the more noise power density will pass, so noise is also a function the bandwidth, see also thermal noise.


Signal to Noise Ratio Displayed in the Frequency Domain


Noise amplitude

Signal to Noise Ratio Displayed in the Time


Signal amplitude