2. What is microwave?
Microwaves are radio waves with wavelengths ranging from lower
boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm).
3. The Doppler Shift
• The wave appears shifted in
frequency from the original,
because of the speed of the
object from which it was
emitted or reflected.
• An increase in frequency
shows an object is moving
toward you.
• A decrease in frequency
shows an object is moving
away from you.
• Click here to see a Doppler
shift video
5. TYPES OF DOPPLER SHIFT
• “Red shift” if v > 0
(moving away)
• “Blue Shift” if v < 0
(moving closer)
6. A SIMPLE EXAMPLE
• A spectral line normally at 4000 angstroms is shifted to 3999
angstroms because of the motion of the source. What is the
velocity of the source, along the line of sight?
• Ans: λ1 = 4000A λ2 = 3999A and c = 3 x 108 m/s
here
= [(3999 – 4000)/4000]•3 x 108
= -7.5 x 104 m/s
7. RADAR(Radio Detection And
Ranging system)
• Radar is an object that uses electromagnetic
waves to identify the range, altitude, direction,
or speed of moving objects such as aircraft,
ships, motor vehicles etc.
8. RADAR contd…..
The basic principle is-
The RADAR dish antenna
transmits pulses of
microwaves which bounce
off any object in their
path.
The transmitted waves
reflect from the object
9. RADAR contd…..
• Constant speed of transmitted waves allows the
determination of the distance between the
reflecting objects (airplanes, ships or cars) and the
radar site by measuring the running time of the
transmitted pulses.
• If there is a frequency shift in the reflected signal
then the reflecting object is moving. By
calculating this frequency shift the radar
determines the speed of the object and its
direction of movement.
10. Some applications
Some applications of velocity measurement using microwave are-
• RADAR gun
• In sports
• Flow measurement of water body
• Off road velocity measurement of vehicles
11. Radar gun
• A radar speed gun is a
small doppler radar unit.
• The radar speed gun was
invented by Bryce K. Brown of
Decatur Electronics in March
1954.
• Used to measure the speed of
moving objects,
including vehicles,
pitched baseballs, runners and
other moving objects.
• Radar speed guns may be
hand-held, vehicle-mounted or
static.
12. Radar gun contd…..
• Measures the speed of objects at which it is
pointed by detecting a change in frequency of
the returned radar signal due to the Doppler
effect.
• Radar speed guns normally operate at X, K, Ka,
IR Band (infrared), and (in Europe) Ku bands.
13. Radar gun working principle
• Radar speed guns consist of a radio
transmitter and receiver.
• They send out a radio signal in a narrow beam,
then receive the same signal back after it
bounces off the target object.
• Due to Doppler effect, if the object is moving ,
the frequency of the reflected radio waves when
they come back is differ from the transmitted
waves.
• From that difference the radar gun can calculate
the object's speed.
14. Radar gun drawbacks
• Radar speed guns do not work reliably in
traffic.
• Significant vehicle separation is essential for
proper operation when used for speed
monitoring by law enforcement personnel.
• The transmitted beam must be highly
directional.
• Antenna size must be small, o higher frquency
of operation.
15. Radar gun correction
• Conventional radar gun limitations are corrected
with a camera aimed along the line of site.
• The radar triggers the camera to take several
pictures when a nearby object exceeds this
speed.
• LIDARs are capable of producing reliable range
and speed measurements in typical urban and
suburban traffic environments without the site
survey limitation and cameras
16. Application in sports
• Baseball with Built-in
Radar Gun measures the
speed of throw.
• Once the ball leaves
your hand, the speed
measurement begins
and when the ball is
caught, the speed of
the throw is displayed
on its LCD screen!
17. Application in sports contd…
• the Baseball Glove Radar
from Sports Sensors puts
pitching speed
measurements literally in
the palm of hand.
• This Doppler radar velocity
sensor brings a new
element to improving skills
in baseball.
• The Glove Radar, reads the
velocity of the ball at the
point just before it is
caught.
18. Application in sports contd…
• Swing speed radar.
• Used in golf to measure
the swing speed of golf
stick.
• Helps to improve swing
speed of the player
19. Application in sports contd…
• A sensor is provided to
measure the speed of a
moving sports object.
• For example the bspeed
of the bullet shot from
a gun or an arrow being
shot from a bow.
20. Application in sports contd…
• Use of microwave to
measure the speed of
an arrow in archery.
21. Application in sports contd…
• The sensor uses CW doppler radar in the form
of a microwave radio frequency transmitter,
and receiver that has a single integrated
antenna/ oscillator.
22. Water flow measurement
• Flow meters use doppler
effect in measuring the
flow.
• Flow meters use this
principle to estimate water
velocity simultaneously at
many points in the cross
section.
24. TARGET TRACKING RADAR (TTR)
• The TTR uses the
designated target
position data (supplied
by whichever
acquisition radar is in
use) to automatically
slew the target track
antenna to the range of
the target.
27. Microwave Motion Sensors for
Off-Road Vehicle Velocity Data and
Collision Avoidance
• Ground Speed Measurement The
conventional way to determine ground speed
is to measure a wheel's rotational velocity
and compute the speed based on the
circumference of the tire. There are two
problems with this method. First, calibration
depends on the type and age of the tire;
second, wheel slippage depends on soil
conditions and the load on the vehicle.
Wheel slippage can average 20%--25% in the
field, although 11%--14% is optimum for the
stress on the vehicle and soil compaction [2].
To help tractor operators optimize vehicle
performance, John Deere has developed a
unit that incorporates a microwave sensor
with a wheel tachometer to calculate wheel
slippage. This unit also provides true ground
speed. According to an extensive study by
California Polytechnic State University at San
Luis Obispo, there is no correlation between
wheel slippage and true ground speed [3].
