neering Research Center (ERC)
called the Center for Collaborative
Adaptive Sensing of the Atmosphere
(CASA) to address this problem.
CASA is researching a new weather
hazard forecasting and warning technology based on a low-cost, dense
networks of radars that operate at
short range, communicate with one
another, and adjust their sensing
strategies in direct response to the
evolving weather and to changing
end-user needs. In contrast to today’s
large weather radars with 10-meter-
diameter antennas, the antennas in
CASA networks are expected to be
one meter in diameter with electronics that are about the size of a personal computer. This small size allows
these radars to be placed on existing
cellular towers and rooftops, enabling
them to comprehensively map damaging winds and heavy rainfall from
the top of storms down to the critical
boundary layer region beneath the
view of current technology. This approach can achieve breakthrough improvements in resolution and update
times, leading to significant reductions in tornado false alarms; quantitative precipitation estimation for
more accurate flood prediction; fine-scale wind field imaging; and the estimation of thermodynamic state variables for use in short-term numerical
forecasting and other applications
such as airborne hazard dispersion
forecasting. Cost, maintenance and
reliability issues, as well as aesthetics,
motivate the use of small (
approximately one-meter diameter, two-de-gree beamwidth) antennas that could
be installed on either low-cost towers
or existing infrastructure elements
(such as rooftops or cellular communication towers).
AESA arrays are
a key enabling technology in many production radars today and a desirable
technology for use
in dense networks
since they do not
require maintenance of moving
parts and they permit flexibility in
beam steering. A
particular challenge
in realizing cost-effective dense net-
works composed of thousands of
radars will be to achieve a design that
can be volume-manufactured for approximately $10,000 per array (
current dollars). Several thousand trans-mit/receive (T/R) channels are needed to realize a phased array capable
of electronically steering a two-de-gree beam in two dimensions over
the desired scan range of these
radars. The realization of such an antenna will benefit from leveraging
commodity silicon RF semiconductors to achieve T/R functions, in combination with very low-cost packaging, fabrication and assembly techniques. Prototypes of the sub-panels
are shown in Figure 4a (front view)
and Figure 4b (rear view).
BEYOND THE
MICROWAVE OVEN
As the pioneer and inventor of the
microwave oven, Raytheon has leveraged high power RF confined in
metallic boxes (or resonant cavities)
to defrost, cook, cure adhesives, etc.
Now and in the future, high power
RF energy may be harnessed to protect airports and stop intruders in
their tracks without killing them. Two
particular systems being examined
are called Vigilant Eagle and Silent
Guardian.
VIGILANT EAGLE
Vigilant Eagle provides an invisible dome of protection around airports or airfields, offering all aircraft—international and domestic
commercial flights, as well as military and private planes—protection
from terrorist surface-to-air missiles
including the Man-Portable Air Defense System (MANPADS). Vigilant
Eagle had already been proven
