Hi my name is Greg Charvat and today we are going
to look through solid concrete walls.
We've developed a phased array radar system
that can look through solid concrete walls.
Our objective is to aid the urban war fighter
to increase his situational awareness.
Rather than using visible light to look through walls,
which is not very effective, we instead use a microwave
wavelength of approximately 10 centimeters.
We radiate a very small signal from this phased array radar
into this solid concrete wall over here.
Of the radiation that we emit at the wall, only point six percent
of that actually gets through the wall itself.
Now, what little energy scatters off the humans behind the wall
has to then go back through the wall.
When it goes back through the wall it again loses
99.4 percent of that energy that was scattered
off the humans, and now this extremely
weak signal comes back through the wall
towards our radar where we receive it.
So what the radar does is it virtually simulates 44 beam
combinations along the aperture of the radar. So what the
national instruments board does, is it actually controls the
switching pattern of those beams and forms a continuous
virtual array of 44 beams which gives us this linear
aperture. And all those beam combinations and beam
samples are then A to D'd [analog to digital]
and acquired by that gaming PC fed into the
imaging algorithms and then displaying in the
user interface that was created to visualize that ten frames
per second of the target scene behind the wall.
Our antenna is made up of lots of little antennas. It's a piece
of printed circuit board, it happens to be white, and it has
these gold traces here, OK, that are conductive.
What happens is there is a piece of coax cable like your
cable television cable, that's soldered to the back of this antenna
and it feeds a microwave signal from our transmitter and
that signal is radiated outward across these two gold-plated
metal traces. And that signal propagates then through free
space to the wall, off the targets and then back.
For the receive antenna, what happens is, microwave energy comes in
to this antenna and is collected all the way down to the back
here and fed into a coax cable where we discriminate and
analyze it digitally later. This is the transmit chassis which
basically sends signals out.
Those are real signals in real time.
So when this one is high this is what's received and
then this is just it resetting itself so right now you see
little signals being received because its going
through the wall and back.
Now the radar does not see things as we humans see things.
This radar image is a top-down view
it's the image plane is in the range away from the radar versus
cross range, across the radar. So what you're seeing is
actual location away from and across.
Currently, when you look at some of the data
from this radar system, what you
see is a little red blob when you have one target behind the wall.
When you have two, you'll see two red blobs and the
blobs move around. What we would like to do in the near
future is we want to implement a detection algorithm
where instead of seeing the blobs you'd see little crosses or squares.