Basic introduction of RADAR

1. RADAR

2. Name : Hitesh D. Chandanshive

3. What is Radar?
• RADAR (Radio Detection
And Ranging) is a way to
detect and study far off
targets by transmitting a
radio pulse in the direction
of the target and observing
the reflection of the wave.
• It’s basically radio echo

4. RADAR
RAdio Detection And Ranging
Radar observables:
• Target range
• Target angles (azimuth & elevation)
• Target size (radar cross section)
• Target speed (Doppler)
• Target features (imaging)
Antenna
Transmitted
Pulse
Target
Cross
Section
Propagation
Reflected
Pulse
(“echo”)

5. Components
• The major components of any radar system
are a radar unit, an antenna, a digital radar
processor and a visual display.
Antenna Processor Display

6. Radar Frequency Bands
Frequency
Wavelength 1 mm1 km 1 m 1 µm 1 nm
1 MHz 1 GHz
IR UV
109
Hz
0 1 2 3 4 5 6 7 8 9 10 11 12
30 20 10 8 6 5 4 39 7
Allocated Frequency (GHz)
Wavelength (cm)
X-BandC-BandS-BandL-BandUHF
VHF
Visible
1012
Hz
Ku
K
Ka
W

7. The Range
• Distance from the radar
• Measured from time
delay between
transmitted pulse and
returned signal received

8. The Range
• Remember, in general v=d/t and d=vt
• The range is just a distance
• Since radio waves travel at the speed of light
(v = c = 300,000 km/sec )
range = c•time/2
• Why divided by 2?

9. Radar Range Measurement
Transmitted
Pulse
Reflected
Pulse
Range
Target
• Target range =
cτ
2
where c = speed of light
τ = round trip time

10. • Atmospheric attenuation
• Reflection off of earth’s
surface
• Over-the-horizon
diffraction
• Atmospheric refraction
Radar beams can be attenuated, reflected and
bent by the environment
Radar beams can be attenuated, reflected and
bent by the environment

11. Radar
• The range and the direction of the target
determine its location, which is what is
needed for many radar applications such as
air traffic control.

12. Types and Uses of Radar
• Search radars scan a large area with pulses of short radio
waves
• Targeting radars use the same principle but scan a smaller
area more often
• Navigational radars are like search radar, but use short waves
that reflect off hard surfaces. They are used on commercial
ships and long-distance commercial aircraft

13. Types and Uses of Radar
• Mapping radar scans a large regions for
remote sensing and geography applications
• Wearable radar which is used to help the visually
impaired
• Air traffic control uses radar to reflect echoes off of
aircraft
• Weather radar uses radar to reflect echoes off of
clouds

14. Types and Uses of Radar
• Weather radars use radio waves with horizontal, dual
(horizontal and vertical), or circular polarization
• Some weather radars use the Doppler effect to measure wind
speeds

15. Incoherent Scatter Echo
• Electrons in ionosphere are
radar targets
• These electrons can scatter
radio waves

17. Weather Radar
A complex instrument but if maintained is stable to about 1-2 dB cf ~100 dB.
Note TRMM spaceborne radar is stable to 0.5 dB
Whistler Radar

18. Thank you !!!