1. RADAR
Department of Electronics and
Telecommunication
Submitted to:- Presented by:-
Mrs.Anjana Jain Aashish patel
Mrs.S.V. Charate 0801EC101001Department
of
Electronics
and
Telecommu
nication
Aashish
Patel
0801EC101
001
2. Content
• Introduction
• History
• Principle
• Radar signal processing
• Classification of radar
• Doppler Effect
• Limiting factor
• Stealth technology
• Application
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.
• Employ EM waves that fall into the microwave
portion of the electromagnetic spectrum
(1 mm < l < 75 cm)
4. Why microwaves?
• Microwaves can penetrate haze, fog and snow
readily, and rain and hail less readily, so radar
can “see through” these conditions.
5. History of RADAR
• Radar was developed for military purposes
during W. W. II.
• The British and US Military used radar to
locate ships and airplanes.
• During the war , radar operator found
annoying blips continually appearing on the
radar screen , scientist had not known that
radar would we sensitive enough to detect
precipitation.
6. Principle of working
• Radar operates on the 3,000 to 10,000 MHz
frequency bands. (super high frequency SHF)
• EM energy radiating outward from a source is
reflected back by objects in its path.
• The time difference between transmission
(trace) and reflection (echo) is measured .
• Distance, azimuth, and elevation can be used
to fix the objects position in three dimensional
space.
7.
8. Radar signal processing
Distance measurement
• Generally 2 method’s are used first Transit
Time and second Frequency Modulation .
• Transmit a short pulse of radio signal and
measure the time it takes for the reflection to
return.
• Accurate distance measurement requires high-
performance electronics.
9. Frequency Modulation
• Frequency comparison between two signals is
considerably more accurate.
• By measuring the frequency of the returned
signal and comparing that with the original,
the difference can be easily measured.
• This technique can be used in continuous
wave radar .
• The amount of frequency shift is used to
measure distance.
10. Speed measurement
• The existing system for measuring distance,
combined with a memory capacity to see
where the target last was, is enough to
measure speed.
• Make use of “DOPPLER EFFECT”.
• In pulse radar, the variation between the
phase of successive returns gives the distance
the target has moved between pulses, and
thus its speed can be calculated.
12. Polarization
• In all electromagnetic radiation the electric
field is perpendicular to the direction of
propagation.
• Radars use horizontal, vertical, linear and
circular polarization to detect different types
of reflections
13. Classification of RADAR
We can classify radar in basically 3 categories……
• Active and passive radar
• Pulse transmission and continuous wave
• Classification on basis of use
14. Active or Passive Radar
• Active radar systems transmit a known signal.
–Most systems are active.
–Such systems can be detected and jammed.
• Passive radar systems rely on ambient signals,
and their reflections.
–Signal processing
• Reference signal and reflection signals
–Hard to detect or jam.
–Efficient power usage
16. Pulse radar
• A pulse generator that discharges timed
pulses of microwave/radio energy .
• Typically radar transmitters send and receive
1500 pulses per second .
• Pulses last about .1 microsecond .
• PW can determine the radar’s minimum range
resolution.
• PRF can determine the radar’s maximum
detection range.
21. Pulse Vs. Continuous Radar
Pulse Echo
• Single Antenna
• Gives Range & Alt.
• Susceptible To Jamming
• Physical Range
Determined By PW and
PRF.
Continuous Wave
• Requires 2 Antennae
• No Range or Alt. Info
• High SNR
• More Difficult to Jam
But Easily Deceived
• Amp can be tuned to
look for expected
frequencies
22. Stealth technology
• Absorbs radar wave or deflect to other
direction.
• Minimizes heat and other emission’s from
engine and other spot’s.
• Make difficult to detect .
• Fly as possible as close to earth surface .
• Make use of RAM (Radar Absorbing Material )
• Shape should be smooth with less edges.
23. Limiting factor’s
• Beam path and range-
As range increases , linear beam get curved because of
change in refractive index of atmosphere .
• Noise-
Internal noise like shot noise , flicker noise etc.
• Interference-
Because of unwanted signal get interfere in radio
wave in atmosphere
• Clutter-
Refers to radio frequency (RF) echoes returned from
targets which are uninteresting to the radar operators
like sand storm , animals , rock , bird’s etc.
24. Jamming-
• Refers to radio frequency signals originating
from sources outside the radar, transmitting in
the radar's frequency and thereby masking
targets of interest
• Jamming may be intentional,
• jamming signal only needs to travel one way
(from jammer to radar receiver)
• jamming can generally only be reduced by
narrowing the mainlobes.
Radar is an object detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter.
Radar signals are reflected especially well by materials of considerable electrical conductivity—especially by most metals, by seawater and by wet lands.
Radar was secretly developed by several nations before and during World War II. The term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging.[1] The term radar has since entered English and other languages as the common noun radar, losing all capitalization.
Wave have different phase b/w transmitted and reflected so don’t get mixed .
They also care about wavelength of radio wave if very small than bounce in many direction and if very large than not get reflected enough to observation with respect to size of target .
Total time divided by 2 b’’coz received pulse consume oth sending and reflecting time .
A further advantage is that the radar can operate effectively at relatively low frequencies.
Pulse-Doppler signal processing
Pulse-Doppler signal processing includes frequency filtering in the detection process. The space between each transmit pulse is divided into range cells or range gates. Each cell is filtered independently much like the process used by a spectrum analyzer to produce the display showing different frequencies. Each different distance produces a different spectrum.
Pt = transmitter power
Gt = gain of the transmitting antenna
Ar = effective aperture (area) of the receiving antenna
σ = radar cross section, or scattering coefficient, of the target
F = pattern propagation factor
Rt = distance from the transmitter to the target
Rr = distance from the target to the receiver.
In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt² Rr² can be replaced by R4, where R is the range.
circular polarization is used to minimize the interference caused by rain. Linear polarization returns usually indicate metal surfaces. Random polarization returns usually indicate a fractal surface, such as rocks or soil, and are used by navigation radars.
Transmitter emits pulses an1. Make copies of graphic and distribute to class.
2. Synchronizer:
a. Coordinates the entire system
b. Determines the timing of the transmitted pulse
c. Includes timers, modulator and central control.
3. Transmitter:
a. Generate the pulses at the proper RF (radio frequency) for the radar.
4. Antenna:
a. Receives energy from the transmitter, radiates it in the form of a
highly directional beam and receives the echoes.
5. Duplexer:
a. Allows one antenna to be used to transmit and receive.
b. Prevents transmitted RF energy from going directly to the receiver.
c. Tells the antenna to radiate or receive.
6. Receiver: receives incoming echoes from antenna, detects and amplifies
the signal, and sends them to the display.
7. Display: Displays the received video to the operator.
8. Power Supply: Provides power to all the components of the system.
9. Discuss the antenna Bearing loop back to the display and its function.
d echos enter in receiver ,displayed on display unit ,synchronizer synchronizes.
PRT=pulse repetition time
PW =pulse width
PRT=1/PRF
When the source of the waves is moving toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave. Therefore each wave takes slightly less time to reach the observer than the previous wave.
a. Frequency expansion is the lowering of the echo frequency caused
by an opening target (target moving away). DOWN DOPPLER
b. Frequency compression is the raising of the echo frequency caused
by the closing target (target moving closer). UP DOPPLER
c. The moving of the transmitter can also cause frequency shifts (it’s
relative motion that produces the effect).
d. The faster the relative motion change the more the frequency shift.
1. Transmit/Receive Antennas. Since must operate simultaneously, must be located separately so receiving antenna doesn’t pick up transmitted signal.
2. Oscillator or Power Amplifier. Sends out signal to transmit antenna. Also sends sample signal to Mixer. (used as a reference)
3. Mixer.
a. A weak sample of the transmitted RF energy is combined with the received echo signal.
b. The two signal will differ because of the Doppler shift.
c. The output of the mixer is a function of the difference in frequencies.
4. Amplifier. Increases strength of signal before sending it to the indicator.
5. Discriminator.
a. Selects desired frequency bands for Doppler shifts.
b. The unit will only allow certain frequency bands so won’t process stray
signals.
6. Indicator. Displays data. Measures radial velocity or the component inbound or directly outbound. Range is not measured.
7. Filters. Used to reduce noise, used in amp to reduce sea return, land clutter, and other non-desirable targets.
PRT=pulse repetition time
PW =pulse width
PRT=1/PRF
Stealth technology is used to hide any plane from radar by given point’s .eg of planes :- F 117 , B-2 Bomber ,F-22 Raptor( From YF 23 Platform), SR-71 Black bird, HMS Helsingborg …..
Beam expand cause reduction in beam concentration and thus do not get effective refection .
Moise like shot noise ,flicker noise,
