Unintentional radiator
Encyclopedia
An unintentional radiator or Incidental radiator is any device which creates radio frequency
energy within itself, which is then unintentionally radiated from the device. This can interfere with other electronic devices and thus can be quite a serious problem at times.
is a typical example, where spurious emission
s may not be contained within the case.
A radio receivers
will often use an intermediate frequency
which is detectable outside the radio—the concept behind at least one audience measurement
concept for roadside detection of radio station
s which passing motorists are listening to.
Other examples include the motor
, transformer
, dimmer
, and corona
from electrical powerlines
. Unintentional radiation from these devices can create interference
on AM radio, and on the video
of television
stations.
regulations and its CRTC equivalents in Canada. Globally, most domestic regulation of unintentional radiators are based on ITU recommendations.
Generally, this means the device leaks a signal at some level. Microprocessor-controlled appliances, anything with a clock signal
, and switching voltage regulators all make some kind of noise, at the repetition frequency and at harmonics. In most countries, government agencies regulate how much leakage is tolerated. This prevents leakage from cable television
systems, for example, from interfering with radio communications between aircraft and control tower
s.
Because it costs money to filter out noise, there is always a balance struck between regulatory compliance and perfect filtering in these devices. Microwave oven
s or devices with microprocessors may leak within allowable limits but may generate an undesired signal that interferes with something in the way of a licensed communications device. It also generally means that users who intentionally radiate signals (TV stations
and cell phone companies) can order the device turned off if it interferes with their licensed operations.
There is an entire industry based on regulatory compliance
: manufacturers shipping a product to a foreign country must comply with each country's limitations on leakage of interfering signals. For example, in Germany the TÜV
issues regulatory rules for unintentional radiators. The big cylindrical bumps on the cable to monitors and laptop chargers are ferrite cores
which reduce undesired signals.
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
energy within itself, which is then unintentionally radiated from the device. This can interfere with other electronic devices and thus can be quite a serious problem at times.
Example radiating devices
A computerComputer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
is a typical example, where spurious emission
Spurious emission
A spurious emission is any radio frequency not deliberately created or transmitted, especially in a device which normally does create other frequencies...
s may not be contained within the case.
A radio receivers
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
will often use an intermediate frequency
Intermediate frequency
In communications and electronic engineering, an intermediate frequency is a frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception. The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called...
which is detectable outside the radio—the concept behind at least one audience measurement
Audience measurement
Audience measurement measures how many people are in an audience, usually in relation to radio listenership and television viewership, but also in relation to newspaper and magazine readership and, increasingly, web traffic on websites...
concept for roadside detection of radio station
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
s which passing motorists are listening to.
Other examples include the motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
, transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
, dimmer
Dimmer
Dimmers are devices used to vary the brightness of a light. By decreasing or increasing the RMS voltage and, hence, the mean power to the lamp, it is possible to vary the intensity of the light output...
, and corona
Corona discharge
In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...
from electrical powerlines
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...
. Unintentional radiation from these devices can create interference
Interference (communication)
In communications and electronics, especially in telecommunications, interference is anything which alters, modifies, or disrupts a signal as it travels along a channel between a source and a receiver. The term typically refers to the addition of unwanted signals to a useful signal...
on AM radio, and on the video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
of television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
stations.
Regulatory overview
In the North America, active devices that are characterized as "unintentional radiators" are governed by Part 15 of the FCCFederal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
regulations and its CRTC equivalents in Canada. Globally, most domestic regulation of unintentional radiators are based on ITU recommendations.
Generally, this means the device leaks a signal at some level. Microprocessor-controlled appliances, anything with a clock signal
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...
, and switching voltage regulators all make some kind of noise, at the repetition frequency and at harmonics. In most countries, government agencies regulate how much leakage is tolerated. This prevents leakage from cable television
Cable television
Cable television is a system of providing television programs to consumers via radio frequency signals transmitted to televisions through coaxial cables or digital light pulses through fixed optical fibers located on the subscriber's property, much like the over-the-air method used in traditional...
systems, for example, from interfering with radio communications between aircraft and control tower
Control tower
A control tower, or more specifically an Air Traffic Control Tower , is the name of the airport building from which the air traffic control unit controls the movement of aircraft on and around the airport. Control towers are also used to control the traffic for other forms of transportation such...
s.
Because it costs money to filter out noise, there is always a balance struck between regulatory compliance and perfect filtering in these devices. Microwave oven
Microwave oven
A microwave oven is a kitchen appliance that heats food by dielectric heating, using microwave radiation to heat polarized molecules within the food...
s or devices with microprocessors may leak within allowable limits but may generate an undesired signal that interferes with something in the way of a licensed communications device. It also generally means that users who intentionally radiate signals (TV stations
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
and cell phone companies) can order the device turned off if it interferes with their licensed operations.
Compliance (regulation)
In general, compliance means conforming to a rule, such as a specification, policy, standard or law. Regulatory compliance describes the goal that corporations or public agencies aspire to in their efforts to ensure that personnel are aware of and take steps to comply with relevant laws and...
: manufacturers shipping a product to a foreign country must comply with each country's limitations on leakage of interfering signals. For example, in Germany the TÜV
Technischer Überwachungsverein
TÜVs are German organizations that work to validate the safety of products of all kinds to protect humans and the environment against hazards. As independent consultants, they examine plants, motor vehicles, energy installations, devices and products TÜVs (short for Technischer...
issues regulatory rules for unintentional radiators. The big cylindrical bumps on the cable to monitors and laptop chargers are ferrite cores
Ferrite bead
A ferrite bead is a passive electric component used to suppress high frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ the mechanism of high dissipation of high frequency currents in a ferrite to build high frequency noise suppression devices...
which reduce undesired signals.