The sensitivity of an electronic device, such as a
communications system
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperat ...
receiver, or detection device, such as a
PIN diode, is the minimum
magnitude of input
signal required to produce a specified output signal having a specified
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 de ...
, or other specified criteria.
Sensitivity is sometimes improperly used as a synonym for ''
responsivity''.
Electroacoustics
The sensitivity of a
microphone
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...
is usually expressed as the
sound
In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.
In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...
field strength In physics, field strength means the '' magnitude'' of a vector-valued field (e.g., in volts per meter, V/m, for an electric field ''E'').
For example, an electromagnetic field results in both electric field strength and magnetic field streng ...
in
decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
s (dB) relative to 1
V/
Pa (Pa =
N/
m2) or as the transfer factor in millivolts per
pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Frenc ...
(mV/Pa) into an
open circuit or into a 1 kiloohm
load.
The sensitivity of a
loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
is usually expressed as dB / 2.83 V
RMS at 1 metre. This is not the same as the
electrical efficiency
The efficiency of a system in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a vulgar fraction, fractional Expression (mathematics), expression), typically denoted by the Gr ...
; see
Efficiency vs sensitivity.
The sensitivity of a
hydrophone is usually expressed as dB re 1 V/μPa.
Receivers
Sensitivity in a receiver, such a
radio receiver
In radio communications, a radio receiver, also known as a receiver, a wireless, or simply a radio, is an electronic device that receives radio waves and converts the information carried by them to a usable form. It is used with an antenna. Th ...
, indicates its capability to extract information from a weak signal, quantified as the lowest signal level that can be useful.
It is mathematically defined as the minimum input signal
required to produce a specified signal-to-noise S/N ratio at the output port of the receiver and is defined as the mean noise power at the input port of the receiver times the minimum required signal-to-noise ratio at the output of the receiver:
:
where
:
= sensitivity
:
=
Boltzmann constant
The Boltzmann constant ( or ) is the proportionality factor that relates the average relative kinetic energy of particles in a gas with the thermodynamic temperature of the gas. It occurs in the definitions of the kelvin and the gas constan ...
:
=
equivalent noise temperature In telecommunications, effective input noise temperature is the source noise temperature in a two-port network or amplifier that will result in the same output noise power, when connected to a noise-free network or amplifier, as that of the actual n ...
in
of the source (e.g. antenna) at the input of the receiver
:
= equivalent noise temperature in
of the receiver referred to the input of the receiver
:
= bandwidth
z:
= Required SNR at output
The same formula can also be expressed in terms of noise factor of the receiver as
:
where
:
=
noise factor
:
= input noise power
:
= required SNR at output.
Because receiver sensitivity indicates how faint an input signal can be to be successfully received by the receiver, the lower power level, the better. Lower power for a given S/N ratio means better sensitivity since the receiver's contribution is smaller. When the power is expressed in dBm the larger the absolute value of the negative number, the better the receive sensitivity. For example, a receiver sensitivity of −98
dBm is better than a receive sensitivity of −95 dBm by 3 dB, or a factor of two. In other words, at a specified data rate, a receiver with a −98 dBm sensitivity can hear signals that are half the power of those heard by a receiver with a −95 dBm receiver sensitivity.
References
{{FS1037C MS188
External links
Microphone sensitivity conversion from dB at 1 V/Pa to transfer factor in mV/Pa
Electrical parameters