In
telecommunications
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...
, insertion loss is the loss of
signal
A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology.
In ...
power
Power may refer to:
Common meanings
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power, a type of energy
* Power (social and political), the ability to influence people or events
Math ...
resulting from the insertion of a device in a
transmission line
In electrical engineering, a transmission line is a specialized cable or other structure designed to conduct electromagnetic waves in a contained manner. The term applies when the conductors are long enough that the wave nature of the transmis ...
or
optical fiber
An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...
and is usually expressed 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, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whos ...
s (dB).
If the power transmitted to the load before insertion is ''P''
T and the power received by the load after insertion is ''P''
R, then the insertion loss in decibels is given by,
:
Electronic filters
Insertion loss is a
figure of merit
A figure of merit (FOM) is a performance metric that characterizes the performance of a device, system, or method, relative to its alternatives. Examples
*Absolute alcohol content per currency unit in an alcoholic beverage
*accurizing, Accuracy o ...
for an
electronic filter
Electronic filters are a type of signal processing filter in the form of electrical circuits. This article covers those filters consisting of lumped-element model, lumped electronic components, as opposed to distributed-element filters. That ...
and this data is generally specified with a filter. Insertion loss is defined as a ratio of the signal level in a test configuration without the filter installed (
) to the signal level with the filter installed (
). This ratio is described in decibels by the following equation:
:
For passive filters,
will be smaller than
. In this case, the insertion loss is positive and measures how much smaller the signal is after adding the filter.
Link with scattering parameters
In case the two measurement ports use the same reference impedance, the insertion loss (
) is defined as:
[Collin, Robert E.; ''Foundations For Microwave Engineering, Second Edition'']
:
.
Here
is one of the
scattering parameters
Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals.
The parameters are useful ...
. Insertion loss is the extra loss produced by the introduction of the
DUT between the 2 reference planes of the measurement. The extra loss can be introduced by intrinsic loss in the DUT and/or mismatch. In case of extra loss the insertion loss is defined to be positive.
See also
*
Mismatch loss
*
Return loss
In telecommunications, return loss is a measure in relative terms of the power of the signal reflected by a discontinuity in a transmission line or optical fiber. This discontinuity can be caused by a mismatch between the termination or load co ...
References
*{{FS1037C
Telecommunications engineering
Engineering ratios