The future of high-frequency, high-speed wireless communications could very well be plasma antennas capable of transmitting focused radio waves that would quickly dissipate using conventional antennas
The different states of matter generally
found on earth are solid, liquid and
gas. Sir William Crookes, an English
physicist, identified a fourth state of
matter, now called plasma, in 1879.
Plasma is by far the most common
form of matter. Plasma in the stars
and in the tenuous space between
them makes up over 99 per cent of the
visible universe and perhaps most of
what is not visible.
Important to antenna technology,
plasmas are conductive assemblies
of charged and neutral particles and
fields that exhibit collective effects.
Plasmas carry electrical currents and
generate magnetic fields.
A plasma antenna is a type of antenna
in which the metal-conducting
elements of a conventional antenna
are replaced by plasma. These are
radio frequency antennas that employ
plasma as the guiding medium for
electromagnetic radiation. The plasma
antennas are essentially a cluster of
thousands of diodes on a silicon chip
that produces a tiny cloud of electrons
when charged. These tiny, dense
clouds can reflect high-frequency
waves like mirrors, focusing the beams
by selectively activating particular
diodes. The ‘beam-forming’ capability
could allow ultra-fast transmission of
high data loads—like those needed
to seamlessly stream a TV show to an
untethered tablet—creating an attractive
option for the next generation of
supercharged wireless transmitters.
Many types of plasma antennas can
be constructed, including dipole, loop
and reflector antennas. Plasma antennas
are interpreted as various devices
in which plasma with electric conductivity
serves as an emitting element.
In gas plasma antenna the concept is
to use plasma discharge tubes as the
antenna elements. When the tubes are
energised, these turn into conductors,
and can transmit and receive radio signals.
When de-energised, these revert
to non-conducting elements and do not
reflect probing radio signals.
The fact that the emitting element
is formed over the interval needed
for the emission of an electromagnetic
pulse is an important advantage of
plasma antennas. In the passive state
(in the absence of plasma in the discharge
tube), such a device does not
exhibit electric conductivity.
A plasma stream flowing from a
jet into the ambient space, the plasma
trace of a body moving at an ultrasonic
velocity in the atmosphere, and
alternative plasma objects have been
studied as possible antenna elements.
Solid-state plasma antenna uses beamforming
technology and the same
manufacturing process that is currently used for silicon chips. That makes it
small enough to fit into smartphones.
Higher frequencies mean shorter
wavelengths and hence smaller antennas...............
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