This document discusses radar technology and stealth technology. It explains how radar works using echo and Doppler shift to detect objects. Radar uses radio waves instead of sound to detect objects from farther distances without disturbing people. Stealth technology aims to make aircraft invisible to radar through shapes that deflect radar signals away and materials that absorb radar signals. Future stealth technology may be used for various military vehicles beyond just aircraft.

1. By Blake Sharin

2. Outline
Background
Radar
How radar works
Echo and Doppler Shift
Understanding Radar
Stealth Technology
History
How it works
Future

3. Who uses Radar Systems?
Radar is used everyday
Air Traffic Control
Police
NASA
Military
Meteorologists

4. Echo and Doppler Shift
Echo occurs because some of
the sound waves in your shout
reflect off of a surface (either the
water at the bottom of the well
or the canyon wall on the far
side) and travel back to your
ears.
The length of time between the
moment you shout and the
moment that you hear the echo
is determined by the distance
between you and the surface
that creates the echo.

5. Echo and Doppler Shift (Contd.)
 Doppler shift occurs when sound is
generated by, or reflected off of, a
moving object.
 Doppler shift in the extreme creates
sonic booms.
 Let's say there is a car coming
toward you at 60 miles per hour
(mph) and its horn is blaring. You
will hear the horn playing one
"note" as the car approaches, but
when the car passes you the sound
of the horn will suddenly shift to a
lower note. It's the same horn
making the same sound the whole
time. The change you hear is caused
by Doppler shift.

6. Echo and Doppler Shift (Contd.)
Combine Echo and Doppler shift
If you send out a loud sound toward a car moving
toward you, some of the sound waves will bounce off
the car (an Echo).
Because the car is moving toward you, the sound waves
will be compressed. Therefore, the sound of the echo
will have a higher pitch than the original sound you
sent.
If you measure the pitch of the echo, you can determine
how fast the car is going.

7. Understanding Radar
 The echo of a sound can be used to determine
how far away something is.
 The Doppler shift of the echo can determine how
fast something is going.
 Sound radar creates what is known as sonar.
› Boats and Submarines
 You could use the same principles with sound in
the air, but sound in the air has a couple of
problems

8. How are Airplanes Measured?
 The idea is for the radar
antenna to send out a burst of
radio energy, which is then
reflected back by any object it
happens to encounter.
 The radar antenna measures
the time it takes for the
reflection to arrive, and with
that information can tell how
far away the object is.
 The metal body of an airplane
is very good at reflecting radar
signals, and this makes it easy
to find and track airplanes
with radar equipment.

9. What are the problems? Solutions?
 Sound doesn't travel very far
› About a mile at the most.
 Almost everyone can hear
sounds, so a "sound radar"
would definitely disturb the
neighbors.
 Because the echo of the sound
would be very faint, it is likely
that it would be hard to
detect.
 Radar therefore uses radio
waves instead of sound.
› Radio waves travel far, are
invisible to humans and are
easy to detect even when they
are faint.

10. Stealth Technology
 The goal of stealth technology is
to make an airplane invisible to
radar. There are two different
ways to create invisibility:
› The airplane can be shaped so that
any radar signals it reflects are
reflected away from the radar
equipment.
› The airplane can be covered in
materials that absorb radar
signals.
 Most conventional aircraft have a
rounded shape. This shape makes
them aerodynamic, but it also
creates a very efficient radar
reflector.
 The round shape means that no
matter where the radar signal hits
the plane, some of the signal gets
reflected back

11. Stealth Technology (Contd.)
A stealth aircraft, on the other
hand, is made up of completely
flat surfaces and very sharp
edges.
 When a radar signal hits a
stealth plane, the signal reflects
away at an angle
Surfaces on a stealth aircraft can
be treated so they absorb radar
energy.
The overall result is that a
stealth aircraft like an F-117A can
have the radar signature of a
small bird rather than an
airplane.

12. Stealth Technology (Contd.)
The only exception is
when the plane banks.
There will often be a
moment when one of the
panels of the plane will
perfectly reflect a burst of
radar energy back to the
antenna.
Is it ironic that stealth
planes resemble UFO
Drawings and sightings?

13. Future of Stealth Technology
In the future, stealth
technology will not
only be incorporated
in fighters and
bombers but also in
ships, helicopters,
tanks and transport
planes.

14. References
http://www.lowobservables.com/
http://people.howstuffworks.com/