Ultra-Wideband Radio
EURASIP Journal on Applied Signal Processing
Ultra-Wideband Radio
Robert A. Scholtz 0 1
David M. Pozar 0 1
0 Department of Electrical Engineering, University of Southern California , Los Angeles, CA 90089 , USA
1 Department of Electrical and Computer Engineering, University of Massachusetts , Amherst, MA 01003 , USA
The application of ultra-wideband (UWB) technology to low-cost short-range communications presents unique challenges to the communications engineer. The impact of the US FCC's regulations and the characteristics of the low-power UWB propagation channels are explored, and their effects on UWB hardware design are illustrated. This tutorial introduction includes references to more detailed explorations of the subject.
and phrases; UWB radio; UWB propagation; UWB antennas; UWB radio architectures; selective RAKE receivers; transmitted-reference receivers
ORIGINS
It has been said that paradigm shifts in design and
operation of systems are necessary to achieve orders-of-magnitude
changes in performance. It would seem that such events
have occurred in the world of radio communications with
the advent of ultra-wideband (UWB) radio. Indeed, several
remarkable innovations have taken place in the brief
history of UWB radio. Initially transient analysis and
timedomain measurements in microwave networks (1960s) and
the patenting of short-pulse (often called impulse or carrierless
or baseband or UWB) radio systems in the early 1970s were
major departures from the then-current engineering
practices. (For detailed descriptions of the early work in this field,
see [
1
].) Marconi’s view of using modulated sinusoidal
carriers and high-Q filters for channelization has so dominated
design and regulation of RF systems since the early
twentieth century, that the viability of short-pulse systems often has
been greeted with skepticism.
Bennett and Ross described the state of UWB engineering
efforts near the end of the 1970s in a revealing paper.
“BA[seband]R[adars] have been . . . recently
demonstrated for various applications, including auto
precollision sensing, spaceship docking, airport
surface traffic control, tanker ship docking, harbor
collision avoidance, etc. These sensing applications cover
ranges from 5 to 5000 ft . . . .
Further applications resulted in the construction of a
sub-nanosecond, single coaxial cable scheme for
multiplexing data between computer terminals . . . . More
recently baseband pulse techniques have been applied
to the problem of developing a short-range wireless
communication link. Here, the low EM pollution and
covertness of operation potentially provide the means
for wireless transmission without licensing.” (From
the Abstract of C. L. Bennett and G. F. Ross,
Timedomain electromagnetics and its applications, Proc.
IEEE, March 1978.)
The early applications of UWB technology were primarily
radar related, driven by the promise of fine-range resolution
that comes with large bandwidth. In the early 1990s,
conferences on UWB technology were initiated and proceedings
documented in book form [
2, 3, 4, 5, 6, 7
]. For the most part,
the papers at these conferences are motivated by radar
applications.
Class/application
Communications and
measurement systems
Imaging: ground penetrating
radar, wall, medical imaging
Imaging: through wall
Imaging: surveillance
Vehicular
3.1 to 10.6 GHz (different out-of-band emission
limits for indoor and outdoor devices)
< 960 MHz or 3.1 to 10.6 GHz
< 960 MHz or 1.99 to 10.6 GHz
1.99 to 10.6 GHz
24 to 29 GHz
User limitations No Yes Yes
Yes
No
Beginning in the late 1980s, small companies, for
example, Multispectral Solutions, Inc. (http://www.multispectral.
com/history.html), Pulson Communications (later to
become Time Domain Corporation), and Aether Wire and
Location (http://www.aetherwire.com), specializing in UWB
technology, started basic research and development on
communications and positioning systems. By the mid-1990s,
when the UltRa Lab at the University of Southern California
was formed (http://ultra.usc.edu/New Site/), lobbying the
US Federal Communications Commission (FCC) to allow
UWB technology to be commercialized was beginning. At a
US Army Research Office/UltRa Lab-Sponsored Workshop
in May 1998, an FCC representative indicated that a notice
of inquiry (NOI) into UWB was imminent, and the
companies working on UWB technology decided to band together
in an informal industry association now known as the
UltraWideband Working Group (http://www.uwb.org). The
objective of this association was to convince the FCC to render
a ruling favorable to the commercialization of UWB radio
systems.
The FCC issued the NOI in September 1998 and within
a year the Time Domain Corporation, US Radar, and Zircon
Corporation had received waivers from the FCC to allow
limited deployment of a small number of UWB devices to
support continued development of the technology, and USC’s
UltRa Lab had an experimental license to study UWB radio
transmissions. A not (...truncated)