In
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than tha ...
, insertion loss is the loss of
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
power 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 transmi ...
or
optical fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparency and translucency, transparent fiber made by Drawing (manufacturing), drawing glass (silica) or plastic to a diameter slightly thicker than that of a Hair ...
and is usually expressed in
decibels (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 is a quantity used to characterize the performance of a device, system or method, relative to its alternatives. Examples
*Clock rate of a CPU
*Calories per serving
*Contrast ratio of an LCD
*Frequency response of a speaker
* Fi ...
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 electronic components, as opposed to distributed-element filters. That is, using component ...
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 f ...
. Insertion loss is the extra loss produced by the introduction of the
DUT DUT is an acronym for
* Da Nang University of Technology in Da Nang, Vietnam
* Dalian University of Technology in Dalian, China
* Delft University of Technology in Delft, the Netherlands
* Device under test, especially in electronics, associated wi ...
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
References
*{{FS1037C
Telecommunications engineering
Engineering ratios