harshal radar

8/13/2019 Harshal Radar

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Radar


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What is Radar?

RADAR (Radio Detection

And Ranging) is a way to

detect and study far off

targets by transmitting a

radio pulse in thedirection of the target and

observing the reflection of

the wave.

Its basically radio echo


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Radar Frequencies


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Radar Frequency Bands

Frequency

Wavelength 1 mm1 km 1 m 1mm 1 nm

1 MHz 1 GHz

IR UV

109Hz

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-BandUHFVHF

Visible

1012Hz

Ku

K

Ka

W


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The Range

Distance from the

radar

Measured from time

delay betweentransmitted pulse and

returned signal

received


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The Range

Remember, in general v=d/t and d=vt

The range is just a distance

Since radio waves travel at the speed oflight (v = c = 300,000 km/sec )

range = ctime/2

Why divided by 2?


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The Range

The 2 is because the measured time is

for a round trip to and from the target. To

determine the range, you only want the

time to the object, so you take half!


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Radar Range Measurement

Target

Target range =c2

where c = speed of light

= round trip time


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Atmospheric Effects


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Atmospheric attenuation

Reflection off of earths

surface

Over-the-horizondiffraction

Atmospheric refraction

Radar beams can be attenuated, reflected and

bent by the environment


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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.
http://southport.jpl.nasa.gov/desc/imagingradarv3.htmlhttp://www.ieee-virtual-museum.org/collection/tech.php?id=2345899&lid=1http://www.ieee-virtual-museum.org/collection/tech.php?id=2345899&lid=1http://southport.jpl.nasa.gov/desc/imagingradarv3.html


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How Strong Is It?

The strength of the received echo can also

be measured

This will vary with the distance of the

target, its size, its shape and its

composition


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Types and Uses of Radar

Search radars scan a large area with pulses of shortradio waves

Targeting radars use the same principle but scan a

smaller area more often

Navigational radars are like search radar, but use shortwaves that reflect off hard surfaces. They are used oncommercial ships and long-distance commercial aircraft


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Mapping radar scans a large regions for remotesensing and geographyapplications

Wearable radar which is used to help thevisually impaired

Air traffic controluses radar to reflect echoes offof aircraft

Weather radar uses radar to reflect echoes off ofclouds
http://www.mywiseowl.com/articles/Remote_sensinghttp://www.mywiseowl.com/articles/Remote_sensinghttp://www.mywiseowl.com/articles/Geographyhttp://www.wearcam.org/ece431/labs/lab3/lab3.htmhttp://www.mywiseowl.com/articles/Air_traffic_controlhttp://www.mywiseowl.com/articles/Aircrafthttp://www.mywiseowl.com/articles/Aircrafthttp://www.mywiseowl.com/articles/Air_traffic_controlhttp://www.wearcam.org/ece431/labs/lab3/lab3.htmhttp://www.mywiseowl.com/articles/Geographyhttp://www.mywiseowl.com/articles/Remote_sensinghttp://www.mywiseowl.com/articles/Remote_sensing


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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
http://localhost/var/www/apps/conversion/tmp/Doppler%20Effect/doppler.ppthttp://localhost/var/www/apps/conversion/tmp/Doppler%20Effect/doppler.ppt


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Incoherent Scatter Radar- A Radar

Application

Used to study the Earth's ionosphere and

its interactions with the upper atmosphere,

the magnetosphere, and the solar wind
http://localhost/var/www/apps/conversion/tmp/scratch_5//hypatia/lmcgourty/The%20Atmosphere.ppthttp://localhost/var/www/apps/conversion/tmp/scratch_5//hypatia/lmcgourty/The%20Atmosphere.ppt


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Incoherent Scatter Echo

Electronsin ionosphere

are radar targets

These electrons can

scatter radio waves
http://www-lab26.kuee.kyoto-u.ac.jp/study/mu/mu_e.htmlhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Radiohttp://www-lab26.kuee.kyoto-u.ac.jp/study/mu/mu_e.html


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Radar Can Measure Pressure

The strength of the echo received from the

ionosphere measures the number of

electrons able to scatter radio waves or

what we call electron pressure
http://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Pressure


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Radar Can Measure Temperature

Some electrons aremoving due to heat- Inthis case the echo isscattered

The echo will contain arange of frequenciesclose to the transmitterfrequency

As the temperature

increases, the electronsmove faster

So radar can act like athermometer and

measure the temperatureof the ionosphere
http://www.energyinfonz.co.nz/home/KidsZone/Energybasics/HE.htmlhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l2b.htmlhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l2b.htmlhttp://www.energyinfonz.co.nz/home/KidsZone/Energybasics/HE.html


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Radar Can Measure Wind Speed

When an electron isremoved from an atom,the remaining chargedatom is called an ion

The ion gas can have a

different temperaturefrom the electron gas

The electron/ion mixtureis known as a plasmaandis usually in motion (likeour wind)

So incoherent scatterradar can also measurewind speed
http://www.chem4kids.com/files/atom_ions.htmlhttp://www.chem4kids.com/files/matter_plasma.htmlhttp://www.chem4kids.com/files/matter_plasma.htmlhttp://www.chem4kids.com/files/atom_ions.html


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