Over the last few years much has been published about the principles and applications of
electromagnetic waves with large relative bandwidth, or nonsinusoidal waves for short. The next
step is the development of the technology for the implementation of these applications. It is
generally agreed that the antennas pose the most difficult technological problem.
Henning F. Harmuth,Antennas and Waveguides for Nonsinusoidal Waves,New York: Academic Press, 1984, p. xi.
More than twenty years after
Harmuth’s observations on the difficulties posed by UWB antenna design and six years after the FCC authorized ultra-wideband (UWB)systems, a variety of UWB
products are nearing wide-scale commercialization. Antenna designers and
engineers have solved the UWB antenna problem in many ways, yielding compact
antennas well suited for a variety of applications. Unlike in previous decades
when UWB antenna progress came in fits and spurts, today there is an active and
growing community of UWB antenna designers sharing their insights and designs
at professional conferences, trade shows, and on the pages of technical
journals.
A keyword search of Google Patents for “UWB antenna” provides quantitative data to
capture these qualitative trends. This metric is somewhat crude and may
overlook certain broadband antenna designs not explicitly labeled as “UWB.”
Similarly, this search may include UWB systems or services that merely mention
“UWB antennas.” Still, this analysis provides an interesting look at trends and
activity in the area of UWB antennas.
Broadband and UWB antennas date back to the earliest days of radio
[1]. Harmuth and others pioneered the use of
impulse or “nonsinusoidal waves” in the 1970’s and 1980’s [2]. The
Time Domain Corporation and Multi-Spectral So-lutions, Inc., were both formed in the late 1980’s tocommercialize UWB technology.
The US Defense
Advanced Research Projects Agency (DARPA) sponsored a review of UWB technology
in 1990 in the context of radar applications [3]. This
investigation was controversial, upholding the merit and value of UWB technology in general, while dismissing some of the extraordinary claims of novel physics made by certain UWBadvocates [4]. By
the early 1990’s, however, terminology had converged towards the use of the
term “ultra-wideband” or “UWB.” The first patent with the exact phrase “UWB
antenna” was filed on behalf of Hughes in 1993. Figure 1 shows the number of US
Patent Applications filed in each year during 1993–2007 containing
the exact search phrase “UWB antenna.”
UWB antenna US patent activity by year (1993–2006).
The 1990’s were
an era of only modest interest in UWB antennas, and only a few US
patent applications were filed. In 1999, however, UWB became front-page news in
USA Today and elsewhere [5]. By
2000, industry leaders like the Time Domain Corporation, Xtreme Spectrum, and
others were engaging in active lobbying of the FCC to open up spectrum for UWB
applications. Their efforts were rewarded by FCC’s Preliminary Report and Order
in 2002 [6].
A surge of UWB patents in 2000 accompanied this in-creased commercial interest. Interest waned
somewhat in 2001, followed by yet another surge in 2002 when the FCC authorized UWB. Interest again waned in 2003 before exploding in 2004 and 2005. The pace of innovation dampened only slightly in 2006. Patents filed in 2007 may not yet
have been published, so complete data is only available through 2006. The
height of the bars in Figure 1 shows the total number of applications filed,
some of which have been issued (dark portion) and some of which are still
pending or were abandoned after publication (light portion). Clearly the US
Patent Office is still dealing with a substantial backlog of UWB-related
patents filed in 2004-2005. Figure 2
shows a cumulative plot of UWB antenna US patent filings.
Cumulative UWB antenna US patent activity by year (1993–2006).
UWB systems have opened up
new dimensions of an-tenna design. Antennas have become an organic part of RF
systems, providing filtering and other custom designed frequency-dependent
properties. The wide bandwidths of UWB antennas present new challenges for
design, simulation, and modeling. Optimizing UWB antennas to meet the demands
of UWB propagation channels is similarlychallenging. And as always, consumer
applications demandcompact and aesthetically pleasing designs that must
nevertheless perform. Designers are meeting these challenges by extending the
bandwidth of familiar antenna architectures like patches and slots. Designers are also using applying familiar techniques like arrays
to UWB applications, as well as employing more recent concepts like antenna
spectral filtering. The time is ripe for a special issue on UWB antennas that
captures this progress and provides insight to where UWB antenna design will
go in the future.
James BeckerDejan Filipovic Hans SchantzSeong-Youp Suh
SchantzH.2005Boston, Mass, USAArtech HouseHarmuthH.1984New York, NY, USAAcademic PressFowlerC. A.EntzmingerJ.CorumJ.Assessment of ultra-wideband (UWB) technology1990511454910.1109/62.63163FowlerC. A.The UWB (impulse) radar caper or ‘punishment of the innocent’19927123510.1109/62.177444ManeyK.Radical new digital technology may revolutionize communications1999AprilU.S. 47 C.F.R. Part 15 Subpart F Section 15.503d Ultra-Wideband Operation