Sensitivity (electronics)
Encyclopedia
The sensitivity of an electronic device, such as a communications system
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
, or other specified criteria.
Sensitivity is sometimes improperly used as a synonym for responsivity
.
Microphone
s
Loudspeaker
s
Hydrophone
s
Sensitivity in a receiver is normally 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 [W]
= equivalent noise temperature in [K] of the source (e.g. antenna) at the input of the receiver
= equivalent noise temperature in [K] of the receiver referred to the input of the receiver
B = bandwidth [Hz]
= Required SNR at output [-]
Because receive 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.
Communications system
In telecommunication, a communications system is a collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment usually capable of interconnection and interoperation to form an integrated whole...
receiver, or detection device, such as a PIN diode
PIN diode
A PIN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts....
, is the minimum magnitude
Magnitude (mathematics)
The magnitude of an object in mathematics is its size: a property by which it can be compared as larger or smaller than other objects of the same kind; in technical terms, an ordering of the class of objects to which it belongs....
of input signal required to produce a specified output signal having a specified signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
, or other specified criteria.
Sensitivity is sometimes improperly used as a synonym for responsivity
Responsivity
Responsivity measures the input–output gain of a detector system. For a system that responds linearly to its input, there is a unique responsivity. For nonlinear systems, the responsivity is the local slope ....
.
Microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
s
- The sensitivity of a microphoneMicrophoneA microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
is usually expressed as the soundSoundSound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
field strengthField strengthIn physics, the field strength of a field is the magnitude of its vector value.In theoretical physics, field strength is another name for the curvature form...
in decibelDecibelThe decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
s (dB) relative to 1 VVoltThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
/PaPascal (unit)The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
(Pa = N/m2) or as the transfer factor in millivolts per pascalPascal (unit)The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
(mV/Pa) into an open circuitOpen circuitThe term Open circuit may refer to:*Open-circuit scuba, a type of SCUBA-diving equipment where the user breathes from the set and then exhales to the surroundings without recycling the exhaled air...
or into a 1 kilohm load.
Loudspeaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s
- The sensitivity of a loudspeakerLoudspeakerA loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
is usually expressed as dB / 2.83 VRMS at 1 metre. This is not the same as the electrical efficiency; see Efficiency vs Sensitivity.
Hydrophone
Hydrophone
A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
s
- The sensitivity of a hydrophoneHydrophoneA hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
is usually expressed as dB re 1 V/µPa.
Sensitivity in a receiver is normally 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 [W]
= equivalent noise temperature in [K] of the source (e.g. antenna) at the input of the receiver = equivalent noise temperature in [K] of the receiver referred to the input of the receiver
B = bandwidth [Hz] = Required SNR at output [-]
Because receive 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
DBm
dBm is an abbreviation for the power ratio in decibels of the measured power referenced to one milliwatt . It is used in radio, microwave and fiber optic networks as a convenient measure of absolute power because of its capability to express both very large and very small values in a short form...
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.