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| Millimeter Wave Radar | |
In the 1950s, expanding upon the radar work started at the
end of World War II, scientists at the Engineering Experiment
Station (now Georgia Tech Research Institute, GTRI) began
investigating use of the millimeter portion of the
electromagnetic spectrum. That work represents significant
contributions to the national technology base and established
Georgia Tech's international reputation in radar research and development.
The advantages of millimeter waves include their ability
to provide accurate, excellent image identification and resolution. They
also provide remote measurements
while operating through smoke, dust, fog or rain. At
the same time, millimeter waves can be vulnerable to absorption by certain
atmospheric and meteorological activity. GTRI scientists learned
which frequencies work best for a particular task and better
identified and refined windows of attenuation — the frequencies
that mitigate atmospheric interference with the signals.
Millimeter wave research at GTRI has been an ongoing
process of discovering the appearance of objects — from tanks to
raindrops — when viewed by high-frequency waves. Researchers
have also determined the types of data — specifically the
absorption and reflection characteristics — they can derive from
the interaction of those objects with the waves. In the process,
they have pioneered the fundamental science of the millimeter
wave environment, while inventing the hardware — antennas,
receivers and transmitters — to use that end of the spectrum.
GTRI built the first military-designation millimeter wave
radar in the late 1950s, followed by a succession of increasingly
advanced models. By the 1980s, ongoing research to build a radar
with a wavelength as near to 1 millimeter as possible culminated
in development of the world's highest-frequency microwave radar,
operating at 225 GHz. The device can provide useful imaging with
an antenna less than 30 centimeters in diameter and is coherent,
meaning it can detect Doppler returns from moving targets.
Research by the late Jim Gallagher in millimeter
spectroscopy paved the way for exploiting millimeter waves for
measurements in radio astronomy, satellite-based studies of the
upper atmosphere, climate, rainfall and vegetation patterns, and
a host of other environmental concerns.
Tech scientists have also achieved a number of firsts in
millimeter characterization of clutter and targets — essential
data for reliable millimeter radar systems. Since the 1960s, more
than a dozen projects have provided millimeter measurements of
the ocean, rain, snow-covered ground, desert, foliage and foreign
military vehicles. In the 1980s, GTRI researchers conducted a
comprehensive study of the image-quality effects of atmospheric
turbulence and precipitation on millimeter wave propagation.
The versatility of millimeter wave technology is
illustrated by the radar flashlight developed at GTRI. It is a
device that detects respiration at a distance. Originally
developed to locate wounded soldiers on a battlefield, it may
prove useful in situations where access is difficult, such as a
collapsed building following an earthquake.
In their ongoing search for more applications of
millimeter wave technology, GTRI scientists are examining its
potential for an automatic target-recognition system, as well as
in various electronic countermeasures and counter-
countermeasures. These include decoy beacons, threat assessment,
reconnaissance and signal disruption.
While innumerable researchers are responsible for GTRI's
national leadership in millimeter wave research and development,
particular recognition belongs to Harold Bassett, Don Bodnar, Ron
Bohlander, Charlie Brown, Clark Butterworth, John M. Cotton, Nick
Currie, Jim Echard, Ron Forsythe, J.J. Gallagher, Bill Holm, Ted
Lane, Robert W. McMillan, Guy Morris, Sam Piper, Ed Reedy, James
Scheer, Bob Trebits and Jim Wiltse.
Georgia Tech file photo
GTRI scientists have used a millimeter wave radar direction
finding system (shown here) to discover the appearance of objects
— from tanks to raindrops — when viewed by high-frequency
waves.
For more information, contact Dr. Ed Reedy, Director, Georgia Tech Research
Institute, Georgia Tech, Atlanta, GA 30332-0801. (Telephone: 404-894-3400)
(E-mail: ed.reedy@gtri.gatech.edu)
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Last updated: October 25, 1999