SSS Online Interview with Dr. Robert Fontana
of Multispectral Solutions
by Jim Pearce, Director, Pegasus
Technologies
In December 2000, I had the pleasure of speaking with Dr. Robert
Fontana about Ultra Wideband (UWB). Bob is the President of
Multispectral Solutions, Inc.
(MSSI) of Germantown, MD. We had a far-ranging conversation on the technical and business
aspects of UWB. Our conversation is summarized below.
Q: How long has MSSI been involved with UWB?
A: We started UWB work in 1984. At first we also used impulse excited antennas like some UWB
proponents are still doing now. When you use this solid state analog of a "spark gap"
approach, the spectrum of the radiated RF is essentially determined by the antenna and you have
very little control over it. This makes it very hard to prevent interference to other radios.
For the last six years we have utilized
a form of UWB where the spectral content of the pulses are determined by electronics using
tapering and shaping. This lets us tailor the spectrum of the RF before it goes to the antenna.
Q.What about the concern that UWB might interfere with
GPS reception? Would you comment on that?
A. Yes, interference is quite possible with impulse excited antenna UWB transmitters.
Public reply comments on the Notice of Proposed Rulemaking published in May to allow UWB
were due in to the FCC October 27, 2000. I think that the only way that the FCC will allow impulse
excited antenna UWB transmitters is at a very, very low power level. There have been a couple of
studies of the power levels at which a UWB transmitter will interfere with GPS and PCS. These
have had conflicting conclusions, but one of them was commissioned by a party with a vested interest
in the outcome. This same party was startled when a major PCS service provider found that impulse
excited antenna UWB had a very detrimental impact on their PCS quality.
Q. What were MSSI's recommendations to the FCC on the future of UWB?
A. We believe that the FCC should allow UWB, but should push it up to above 3GHz. This way it
will be above the critical frequencies for GPS and PCS and will be a win-win for both UWB and GPS users.
Q. Some companies are using a form of pulse position modulation to
encode data on their UWB signals. Is this the modulation technique that MSSI uses?
A. No. They move a pulse a few picoseconds before or after it should arrive and code binary
data this way. The problem with this is that multipath environments will cause delay spreads
of up to several hundred nanoseconds. This will not only cause the data to be decoded
improperly, but also will cause the receiver to lose sync.
Q. What modulation technique does MSSI use?
A. We use a very simple amplitude modulation on/off keying. Using our tunnel quantum detector,
we find this to be a very satisfactory method of sending data. It's very similar to the way that
optical fiber systems work. Of course, optical fiber also uses wavelength division
multiplexing. We can also do this, since we can control the center frequency of our UWB signal.
Q. Some UWB companies use PN codes to encode the time between pulses.
Do you do this?
A. No, we use the on/off keying at a fixed pulse repetition rate, and transmit data in short
packets. We also use pulse dithering for some of our more specialized systems.
Q. Who are MSSI's customers for UWB?
A. For our first 10 years, the work was classified at a fairly high level. We did a lot
of "spook" work. Since 1995, much of the new work was done at the unclassified level.
The vast majority of our work continues to be for the U.S. government and military.
Q. What do you think are the most exciting applications for UWB
in the future?
A. We think that the really exciting possibilities for UWB are where communication, radar,
and position localization can all be combined in small devices -- applications like tagging
vehicles or even a device that would help blind people navigate by identifying obstacles and
having position tags that would let them know, for example, that they are at the east entrance
of Sears.
Q. How about ID tag location?
A. I'm glad that you mentioned that. You know that the Navy had tons of stuff that they
moved to Saudi Arabia during the Gulf War. There were billions of dollars of goods that they
couldn't find. To avoid this problem in the future, the Navy asked us to participate in a
program to develop ID tags that could locate crates on ships to sub-foot resolutions.
Another company using conventional spread spectrum also participated, but they could not achieve
the type of resolution achievable with our UWB system.
Q. Do you think UWB will be widely used for high speed data?
A. There are definite issues with using UWB for very high speed data.
For instance, since the receive bandwidth is high, KTB (Boltzman's Constant, times temperature,
times bandwidth) noise is also high. Also, channelization can be difficult with UWB since such
wide instantaneous bandwidths are used. This being said, UWB does have great potential for high
speed, wireless communications -- particularly in the presence of multipath -- with the proper
architecture.
Q. What distinguishes MSSI from other companies in the UWB field?
A. We have been building UWB systems for more than 11 years. We are not a start-up and we are
not funded by venture capital. We don't have shareholders to satisfy, so we can concentrate on
satisfying our clients. We have successfully performed on dozens of projects, each of which has
resulted in tangible and useful hardware.
Q: Thank you, Dr. Fontana. It's been a pleasure talking to you.
A: It's been my pleasure.
Dr. Robert J. Fontana
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Dr. Fontana, MSSI's
founder, earned a BSEE with honors from the Illinois Institute of
Technology, receiving a fellowship to study at the Institut National
des Sciences Appliquées (Lyon, France) during his junior year. He
received the SMEE degree from the Massachusetts Institute of
Technology, and a Ph.D. degree in Electrical Engineering from Stanford
University. Bob has over twenty-eight years of experience in the areas
of signal processing, high-speed digital design, microwave/RF design,
and ultra wideband technology.
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