Infrared headset nixes radiation
Technology Research News
Hands-free headsets may help you keep your
eyes on the road and hands on the wheel, but the devices may also be exposing
you to electromagnetic stress by amplifying the phone’s radiation.
A headset connects to the phone by an electrical wire. Research
has shown that the wire can act as a conduit for microwave radiation,
which has been tagged as a possible health risk. The earpiece of traditional
cell phones also contains an electromagnetic coil that turns electrical
signals into audible signals but in doing so gives off electromagnetic
Borrowing from the field of optical communications, a researcher
at the University of Warwick in England has devised a hands-free cell
phone that sidesteps the problem by eliminating the headset wire and the
earpiece electromagnetic coil.
The device replaces the headset wire with a five-millimeter plastic
pipe that carries infrared, or heatwave, signals. There is no radiation,
because there is no conductive link through wire, said Roger J. Green,
a professor of electronic communication systems at the University of Warwick.
The device converts electrical signals to infrared signals, sends
the signals through the pipe, detects the infrared signals and converts
them back to electrical signals. “We use light-emitting diodes to convert
electrical signals into infrared [and] photodetectors to convert light
back into electrical signals,” Green said.
Infrared radiation falls between visible lightwaves and microwaves
on the electromagnetic spectrum. Visible light has higher frequencies
and shorter wavelengths than infrared light, which has higher frequencies
and shorter wavelengths than microwaves.
A communication using Green's device involves two sets of infrared
beams: one for the microphone-to-phone link, and the other for the phone-earphone
link. Green's device also uses a piezoelectric crystal instead of an electromagnetic
When a person speaks into a cell phone, the sound waves of speech
hit a tiny diaphragm in a microphone, causing vibrations that are converted
to electrical signals.
In conventional headsets, electrical signals from the remote caller
are converted back to sound by reversing the process: an electromagnetic
coil moves a tiny diaphragm in sync with the electrical signals. The motion
of the diaphragm varies according to the electrical signal, and so “reproduces
the sound wave by compressing and decompressing the air just above it
at a rapid rate,” said Green.
The electromagnetic coil, however, produces electromagnetic radiation.
“A headset with a coil in the earpiece has an antenna which can pick up
electromagnetic radiation," he said. "This could radiate into the head."
Replacing the earpiece electromagnetic coil with a piezoelectric
crystal eliminates the electromagnetic radiation altogether. "There is
no antenna effect in the earpiece,” said Green. “There is no radiation
at the earphone due to any radio frequency (RF) energy.”
Piezoelectric materials, such as the crystals used in watches
do not conduct electricity, but instead expand and contract in the presence
of an alternating electric charge; these physical vibrations generate
high-frequency sound waves.
Though no medical evidence correlating brain tumors and cell phone
usage is of long-term significance yet, replacing the questionable components
of cell phones is an obvious way to stay on the safe side, said Green.
The trick to designing a headset that does not conduct or emit
electromagnetic radiation was making the connection between the two subject
areas of optical and radio communications, said Green. Once both fields
are involved, "the problem is solved cheaply and effectively,” he added.
The headset could be used with any mobile phone on the market
today, according to Green. "It is ready for commercialization," he said.
The headset component cost is slightly higher than that of traditional
headset phones, but the end-product should be only slightly more expensive,
This technique of converting radio frequency into infrared could
also be used in other types of electronics in order to shield users from
electromagnetic radiation, said Green.
The research was funded by the University of Warwick and Warwick
Funding: University; Corporate
TRN Categories: Engineering and Optical Computing; Optoelectronics
Story Type: News
Related Elements: None
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