TECH KNOWLEDGEY
EVENTS, ADVANCES, AND NEWS
2010
■ BY JEFF ECKERT
ADVANCED TECHNOLOGY
WIPING OUT WIRING, PART 1
With the development of wireless routers, Bluetooth devices, wireless keyboards, et al., we've made
pretty good progress in the quest to eliminate all those
pesky wire interconnects in the office. But some Purdue
University ( www.purdue.edu) researchers are working
on a technology that could cut the communications
copper for all of the devices in your home or office,
including HD TV, radio, projectors, and whatever. The
idea is to transmit all communications from a single base
station which would consist of a dedicated computer or
perhaps just a card inserted into an expansion slot in an
existing one.
"The central computer would take charge of all the
information processing, a single point of contact that
interacts with the external world in receiving and sending
information," according to Prof. Minghao Qi. We're not
talking about conventional RF technology, however.
Rather than operating in the noisy 2. 4 GHz band, the
Purdue system transmits at 60 GHz. This is accomplished
■ Diagram
of a silicon
“microring
resonator” that
enables fast
laser pulses to
be converted
to RF signals.
PHOTO COURTESY OF PURDUE UNIVERSIT Y.
by converting ultrafast laser pulses into RF signals using
newly developed "microring resonators" that sidestep the
limitations of standard digital-to-analog converters, and
eliminate the need for large "bulk optics" systems that use
optical components to achieve the same thing. By
combining a series of microrings into a programmable
"spectral shaper," the system can be set to transmit only
certain frequencies. Because no one — including the FCC
— regulates signals in the range of 57 to 64 GHz, the
system could be implemented on a worldwide basis with
universal compatibility. Purdue filed for a provisional
patent last January, but Qi noted that the technology is
still at least five years away from commercialization. ▲
WIPING OUT WIRING, PART 2
Taking a more direct approach to converting light into broadband is a concept recently demonstrated by Jelena Vucic and associates, of the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute ( www.hhi.fraunhofer.de).
The idea here is to harness things like simple desk lamps to transmit visible-frequency wireless data. You simply impose
high frequency flicker on all of the lights in a room in unison. A minor snag is that incandescent and fluorescent lights
aren't capable of flickering fast enough, so the lights have to be LED based. Although present commercial LEDs have a
limited bandwidth, the Fraunhofer researchers have achieved a tenfold bandwidth increase by filtering out the blue part
of the spectrum. Their first wireless system achieved data rates of 100 Mb/s in the lab, and the latest upgraded system
has hit 230 Mb/s. This still isn't earth-shattering speed, but Vucic says a more sophisticated modulation signal should
allow the rate to be doubled again. An interesting consideration is that — unlike RF signals — visible-light transmissions
cannot pass through walls or other opaque barriers. That's both a limitation and an advantage, though, as securing your
facility against eavesdroppers would be pretty much just a matter of closing your curtains. ▲
MAXWELL’S DEMON DISCOVERED?
Ateam at Massachusetts Institute of Technology ( www.mit.edu) has figured out a way to transform polyethylene — usually a great electrical insulator but poor heat conductor — into a material that can dissipate heat as well as most
metals. This has obvious potential in applications ranging from heatsinks in electronics to solar collectors and heat
exchangers. The interesting facet is that (according to MIT) the material will "conduct heat very efficiently in just one
direction unlike metals which conduct equally well in all directions." This sounds eerily similar to James Clerk Maxwell's
hypothetical concept of a two-chambered box in which a gatekeeper (the demon) would allow only high velocity
molecules to pass from chamber A to B and low velocity ones from B to A, thus increasing the temperature in B and
lowering it in A. This would provide an exception to the second law of thermodynamics. Can the MIT material qualify
as the demon? Well, not likely. But it should make one heck of a thermos bottle. ▲
10
May 2010
