T E C H N I C A L
“The technology could enable a network of devices to communicate with
no power source”
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The scientific
imagination always
restrains itself within
the limit of probability
AMBIENT BACKSCATTER-Communication without Batteries
Using ambient backscatter, devices absorb signals and then reflect them to
each other to communicate. They do not generate their own signals, so no
battery power is required.
The researchers built small, battery-free devices with antennas that can
detect, harness and reflect a TV signal, which then is picked up by other
similar devices. The technology could enable a network of devices and
sensors to communicate with no power source or human attention needed.
Devices form a network out of thin air. You can reflect these signals
slightly to create a code of communication between battery-free devices.
The researchers tested the ambient backscatter
technique with credit card-sized
prototype
devices placed within several feet of each other.
For each device the researchers built antennas
into ordinary circuit boards that flash LED
light when receiving a communication signal
from another device. Groups of the devices were
tested in a variety of settings, including inside an
apartment building, on a street corner and on the
top level of a parking garage.
The receiving devices picked up a signal from
their transmitting counterparts at a rate of 1
kilobit per second when up to 2.5 feet apart
outdoors and 1.5 feet apart indoors. This is
enough to send information such as a sensor
reading, text messages and contact information.
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Receiver
Transmitter
Future Uses
1)
It could be configured with phones, to send text messages by
leveraging power from an ambient TV signal.
2)
If a person loses his keys, their couch can use it to
communicate with the keys and alert the users smartphone.
3)
Finds applications in areas including wearable computing,
smart homes and self-sustaining sensor networks.
4)
It can be used inside structures to create a network of sensors
for home monitoring and industrial detection.
The new device laden with light-emitting diodes and sensors, both the size of
individual brain cells, promises to make optogenetics completely wireless.
The 20-micrometer-thick device can be safely injected deep into the brain
and controlled and powered using radio-frequency signals. The technology
could also be used in other parts of the body.
FARADAY CAGE CRACKED
Engineers in Cambridge have discovered a way to break through
the
Faraday Cage that prevents the entry or escape of an
electromagnetic field through a metallic enclosure. The Technology
Partnership (TTP) believes this could have
potential benefits for
power and data transfer through metal shielding.
The company’s Fluxor method creates a ‘window’ for
electromagnetic transmission of power and data by applying
a strong DC magnetic field, which lines up the magnetic dipoles in
the material to ‘saturate’ a small area of the metal screen. This
reduces the permeability and increases penetration to make it
possible to transfer electromagnetic power and signals.
Faraday cage in
the absence of
an electric field
The
charged
particles in the
wall of Faraday
cage respond to
an
applied
electric field
Electric
fields
generated inside
the wall cancel out
the applied field,
neutralizing
the
interior of the cage
Experiments conducted by TTP using steels from 5-15mm thick shows that the optimum operating frequency range is in
the region of 400-500Hz. In a typical operating scenario, a portable interrogator unit with a permanent magnet or
electromagnet could be placed on top of a fixed sensor through a metal wall. A Fluxor window is opened to transmit
power to energise the sensor and transmit a signal back – all without the need of physical openings in the enclosure.
THE ELECTRONICLE XV
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