CEE431 Radar Systems

Instructed By
Dr. Ahmed Azzam
Electronics and Communication Department
Theba Higher Institute of Engineering
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 References
1. Essential Text Book { Merrill L. Skolnik, Introduction to Radar Systems, 3rd Edition, 2001}

2. Recommended Book { Eyton Z. Peebles, Radar Principles, Wiley Interscience, 1998}

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 LEC. 1
Introduction of Radar

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Lec. Outlines
Historical overview
Basics of Radar systems
Working of Radar systems
Advantages of Radar Systems
Limitation of Radar systems
Application of radar systems
Radar functions
Radar Classification
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 A HISTORICAL OVERVIEW

Neither a single state nor a single person is able to say, he is the inventor of the radar
method.
The radar is a result of an accumulation of many developments and improvements,
which scientists of several nations parallelly made share.
There are several milestones with the discovery of important basic knowledge and
important inventions.
Driven by the war interests and the general development of the air forces to meaning
key players radar technology undergo a strong development push during the
2nd's World War.
After the 2nd World War the radar method is put into “peace use”.

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 1865-The English physicist James Clerk Maxwell developed his electric magnetic
light theory (Description of the electric magnetic waves and her
propagation)

1886-The German physicist Heinrich Rudolf Hertz discovers the electro magnetic
waves and prove the theory of Maxwell with that.

1904-The German high frequency technician Christian Hülsmeyer invents the

“Telemobiloscop” to the traffic supervision on the water. He measures the
running time of electric magnetic waves to a metal object (ship) and back.
A calculation of the distance is thus possible. This is the first practical radar
test. Hülsmeyer patented his invention.

1921-The invention of the Magnetron as an efficient transmitting tube by

Albert Wallace Hull

1922-A. H. Taylor and L.C.Young of the Naval Research Laboratory (USA)

locate a wooden ship for the first time Japan

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 1930-L. A. Hyland (also of the Naval Research Laboratory), locates an
aircraft for the first time

1931-A ship is equipped with radar. As antennae parabolic dishes with

horn radiators are used

1936-The development of the Klystron by Metcalf and Hahn. This will be

an important component in radar units as an amplifier or an
oscillator tube.

1940-Different radar equipments are developed in the USA, Russia,

Germany, France and Japan
1941-Radar Meteorology at Radiation Laboratory –MIT

1942-The old B-18s carried the first operational aircraft microwave

radar, the S-band SCR-517.

1944-Radar training of the Army Air Corps Weather Officers

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 1946-Postwar research and development –Weather Radar in the Radar
Branch, Signal Corps Laboratories.

1946 -The Weather Radar Research Project in the Department of

Meteorology of MIT

1950-Weather Radar in the Meteorological Branch, Meteorological Division

and Atmospheric Sciences Laboratory, Fort Monmouth USA

1954 -First Japanese X-band weather radar built by JRC

1954-Establishment of Meteorological Radar Network in India

1958-British Weather Radars installed in Shanghai and Beijing.

1964-Radar Meteorology at the National Severe Storms Laboratory

1977-First research Weather Radar in São Paulo –Brazil

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Radar Principle
The electronic principle on which radar operates is very similar to the principle of
sound-wave reflection.
If you shout in the direction of a sound-reflecting object (like a rocky canyon or
cave), you will hear an echo.

If you know the speed of sound in air, you can then estimate the distance and
general direction of the object.

The time required for an echo to return can be roughly converted to distance if
the speed of sound is known.

Radar uses electromagnetic energy pulses in much the same way. Radar sets use
the echo to determine the direction and distance of the reflecting object.

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 Basics of Radar systems

Radar is an object-detection system that uses radio waves to determine the range,
angle, or velocity of objects.

It can be used to detect many objects such as aircraft, ships, spacecraft, guided
missiles, motor vehicles, weather, and terrain.
Radar is acronym for RAdio (Aim) Detecting And Ranging.
Radar was developed secretly for military purpose during the world 2nd war.

The EM energy “reflected” from the target is analyzed by the receiving part
of the device in such a way that characteristics of the target may be
determined.

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 Radar Operation
Radar is an electromagnetic sensor for the detection and
location of reflecting objects. Its operation can be summarized
as follows:
1- The radar radiates electromagnetic energy from antenna to
propagate in space.
2- Some of the radiated energy is intercepted by a reflecting object,
usually called a target, located at a distance from the radar.
3- The energy intercepted by the target is reradiated in many
directions.
4- Some of reradiated (echo) energy is returned to and received by
the radar antenna.

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 Radar Operation
Radar is an electromagnetic sensor for the detection and
location of reflecting objects. Its operation can be summarized
as follows:

5- After amplification by a receiver and with the aid of proper

signal processing, a decision is made at the output of the
receiver as to whether or not a target echo signal is present. A
that time, the target location and possibly other information
about the target is acquired.

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 Radar Operation

transmitted energy

backscatter

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Radar Operation
1- The distance to the target is determined by measuring the time
taken for the radar signal to travel to the target and back.
2- The direction, or angular position, of the target may be
determined from the direction of arrival of the reflected
wavefront.
3- The usual method of measuring the direction of arrival is with
narrow antenna beams. If relative motion exists between
target and radar, the shift in the carrier frequency of the
reflected wave (doppler effect) is a measure of the target's
relative (radial) velocity and may be used to distinguish moving
targets from stationary objects.
4- In radars which continuously track the movement of a target, a
continuous indication of the rate of change of target position is
also available.
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 Radar Basic Block Diagram

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 Advantages of Radar Systems
Radar can see through darkness, haze, fog, rain, and snow.
Radars can determine the position, range, angle, and velocity
of object.

Limitation of Radar systems

Radar cannot resolve in details like the human eye, especially
at short distance.
Radar cannot recognize the color of the target.
Radar cannot identify internal aspect of the target.

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 Civilian Applications
Navigational aid on ground and sea.

Radar altimeters for determine the height of plane

above ground.

Police radars for detecting speeding vehicles.

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 i
r
e
c
t
Military Applications
i
n Detecting and ranging of enemy targets.
g
Aiming fires (gun, missile, artillery,…) on aircraft and
o
r ships.
g Bombing aircrafts, and ships even at night.
u
i Early warning regarding approaching troops, aircraft,
d
i and ships.
n
g
Directing or guiding missiles.
m
i
s
s
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Radar Functions
• Normal radar functions:
1. range (from pulse delay)
2. velocity (from Doppler frequency shift)
3. angular direction (from antenna pointing)
• Signature analysis and inverse scattering:
4. target size (from magnitude of return)
5. target shape and components (return as a function of direction)
6. moving parts (modulation of the return)
7. material composition
• The complexity (cost & size) of the radar increases with the extent
of the functions that the radar performs.
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 CLASSIFICATION ACCORDING T0 THEIR FUNCTION

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 PRIMARY RADAR

A primary radar transmits high-frequency signals which

are reflected at targets.

The arisen echoes are received and evaluated.

This means, unlike secondary radar units a primary radar

unit receive her own emitted signals as an echo again.

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 SECONDARY RADAR

RADAR At these radar units the airplane must have a

transponder(transmitting responder) on board and
receives an encoded signal of the secondary radar unit.

An active also encoded response signal which is returned

to the radar unit then is generated in the transponder.

In this response can be contained much more information,

as a primary radar unit is able to acquire (E.g. an altitude,
an identification code or also any technical problems on
board such as a radio contact loss ...).
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PULSE RADARS

Pulse radar is a primary radar unit which transmit a high-frequency

impulsive signal of high power.

After this a longer break in which the echoes can be received follows
before a new transmitted signal is sent out.

C.W RADAR
CW radar units transmit a high-frequency signal continuously.

The echo signal permanently is received and processed.

The receiver needn't be mounted at the same place as the

transmitter absolutely.
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Unmodulated CW RADAR

The transmitted signal of these equipments is constant in amplitude and frequency.

These equipments are mostly used in speed measuring.

Distances cannot be measured. In general are used as speed gauges of the police.

Modulated CW-Radar
The transmitted signal is constant in the amplitude but modulated in the frequency.

This uses the principle of the propagation time measurement.

The advantage of these equipments is that the measurement result is continuously

available.

Distances can be measured, The amount of spectrum spreading caused by modulation riding on the
receive signal is proportional to the distance to the reflecting object.
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 CLASSIFICATION ACCORDING T0 THEIR Antenna Type

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 CLASSIFICATION ACCORDING T0 THEIR Antenna Type

Bistatic: The transmit and receive antennas are at different locations as

viewed from the target (e.g., ground transmitter and airborne receiver).

Monostatic: The transmitter and receiver are collocated as viewed from

the target (i.e., the same antenna is used to transmit and receive).

Quasi-monostatic: The transmit and receive antennas are slightly

separated but still appear to be at the same location as viewed from the
target (e.g. separate transmit and receive antennas on the same
aircraft).

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 Monostatic Radar Bistatic Radar
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Continuous-wave radar
Continuous-wave radar is a type of radar system where a known stable
frequency continuous wave radio energy is transmitted and then received from
any reflecting objects. Continuous-wave (CW) radar uses Doppler, which
renders the radar immune to interference from large stationary objects and slow
moving clutter.
The main advantage of CW radar is that energy is not pulsed so these are much
simpler to manufacture and operate.

They have no minimum or maximum range, although the broadcast power level
imposes a practical limit on range.
The military uses continuous-wave radar to guide semi-active radar
homing (SARH) air-to-air missiles, such as the U.S. AIM-7 Sparrow

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Continuous-wave radar

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 End of Lecture
Thank You

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