With more wireless connections being integrated into
a wide range of products, many are looking for a
wireless technology that can handle higher data rates
approaching 1 Gb/s. All of the currently proposed
solutions to meet that goal are focused on ultra-wideband (UWB) transmission systems.
The concept of UWB communication originated in the
early days of radio. In the 1900s, the Marconi spark
gap transmitter (the beginning of radio) communicated
by spreading a signal over a very wide bandwidth. In
the 1940's, Claude Shannon said the most efficient
communication was "down in the noise". His
"Mathematical Theory of Communication" explains
that information carrying capacity may be increased by
either widening the bandwidth or increasing the complexity
of modulation. While most radio transmission is
high power density with low bandwidth, an alternative
would be low power density with wide bandwidth.
The communications world abandoned wideband
in favor of narrowband or tuned radios in which, in
the case of the U.S., the Federal Communications
Commission governed spectrum allocation. The
incidental radiated power limits were the motivation
for various organizations to challenge the paradigm of
narrowband communications, in an ongoing effort to
squeeze capacity out of a highly regulated spectrum.
Many companies argued that they should be allowed
to intentionally transmit at the incidental radiated
power limits over an ultra-wide bandwidth to take
advantage of this capacity potential. This argument
was the motivation for the FCC approval of UWB. In
February, 2002, the FCC amended their Part 15 rules
(concerning unlicensed radio device) to include the
operation of UWB devices without a license.
UWB technology is expected to achieve data rates in
excess of 1 Gb/s over short distances at low power.
This makes UWB a practical alternative to high speed
cabling. UWB has been demonstrated in a wide variety
of electronics devices including digital audio-visual
equipment, mobile phones, and PCs using wireless USB.
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Application Note: Ultra-Wideband RF Measurements