RADAR

DOPPLER EFFECT

How Radar Works?

• It is named after the Austrian physicist Christian Doppler, who proposed it in 1842.

• The Doppler Effect (Doppler Shift) is the apparent change in the frequency of the wave caused by a relative motion between the source of the wave and the observer.

The basic idea behind radar is very simple: a signal is transmitted, it bounces off an object and it is later received by some type of receiver.

Jamming

• Radar jamming refers to radio frequency signals originating from sources outside the radar, transmittinig in the radar's frequency and thereby masking targets of interest.

• Jamming is problematic to radar since the jamming signal only needs to travel one way (from the jammer to the radar receiver) whereas the radar echoes travel two ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver.

• Mainlobe Jamming can generally only be reduced by narrowing the mainlobe solid angle and cannot fully be eliminated when directly facing a jammer which uses the same frequency and polarization as the radar.

Maximum Range - The maximum range of convential radar can be limited by a number of factors:

• Line of sight, which dependson height above ground. This means without a direct line of sight the path of the beam is blocked.

• The maximum non-ambiguous range, which is determined by the pulse repetition frequency. The maximmum non-ambiguous range is the distance the pulse could travel and return before the next pulse is emitted.

• Radar sensitivity and power of the return signal is computed in the radar equation. This includes factors such as environmental conditions and the size (or radar cross section) of the target.

Echo and Doppler Shift - The echo occurs because some of the sound waves in your shout reflect off of a surface and travel back to your ears.

Clutter may also originate from multipath echoes from valid targets caused by ground reflection, atmospheric ducting or ionospheric reflection/refraction (e.g, anomalous propagation).

Noise

• Signal Noise is an internal source of random variations in the signal, which is generated by all electronic components.

• Reflected Signals decline rapidly as distance increases, so noise introduces a radar range limitations.

• Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver.

• Shot Noise is produced by electrons in transit across a discontinuity, which occurs in all detectors.

• Noise is also generated by external sources, most importantly the natural thermal radiation of the background surrounding the target of interest.

• Noise is random and the target signals are not.

PARTS OF RADAR

Interference

• Radar systems must overcome unwanted signals in order to focus only on the actual targets interest.

Clutter

• Clutter refers to radio frequency (RF) echoes returned from targets which are uninteresting to the radar operators.

• Some clutter may also be caused by a long radar waveguide between the radar transceiver and the antenna.

• Clutter is detected and neutralized in several ways/

• Clutter moves with the wind or is stationary. Two common strategies to improve measure or performance in an clutter environment are:

-Moving traget indication, which integrates successive pulses and;

-Doppler Processing, which uses filters to separate clutter from desirable signals.

Doppler Shift - This occurs when sound is generated by, or reflected off of a moving object.

*Doppler shift example:

• The person behind the car hears a lower tone than the driver because the carr is moving away. The person in front of the car hears a higher tone than the driver because the car is approaching.

PRINCIPLES OF RADAR

Reflection

• If electromagnetic waves travelling through one material meet another material, having a very different dielectric constant or diamagnetic constant from the first, the waves will reflect or scatter from the boundary between the materials

• Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target

• Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass

Transmitter - The radar transmitter produces the short duration high-power rf pulses of energy that are into space by the antenna.

Radar Signal

• transmitter that emits radio waves called radar signals in predetermined directions

• Radar signals are reflected especially well by materials of considerable ellectrical conductivity

• The radar signals that are reflected back towards the transmitter are the desirable ones that make radar work

Illumination

• Radar relies on its own transmissions rather than light from the sun or the Moon, or from electromagnetic waves emitted by the objects themselves

• This process of directing artificial radio waves towards objects is called illumination

Receiver - amplify and demodulate the received RF-signals. The receiver provides video signals on the output.

Duplexer- alternately switches the antenna between the transmitter and receiver so that only one antenna need be used. This switching is necessary because the high-power pulses of the transmitter would destroy the receiver if energy were allowed to enter the receiver.

Indicator - should present to the observer a continuous, easily understandable, graphic picture of the relative position of radar targets.

The radar screen (in this case a PPI-scope) - displays the produced from the echo signals bright blibs. The longer the pulses were delayed by the runtime, the further away from the center of this radar scope they are displayed. The direction of the deflection on this screen is that in which the antenna is currently pointing.

Radar Antenna -transfers the transmitter energy to signals in space with the required distribution and efficiency. This process is applied in an identical way on reception

BASIC RADAR SYSTEM

Group 1

• Everything starts with the transmitter as it transmits a high power pulse to a switch which then directs the pulse to be transmitted out an antenna.

• Just after the antenna is finished transmitting the pulse, the switch switches control to the receiver which allows the antenna to recieve echoed signals.

• Once the signals are received the switch then transfers control back to the transmitter to transmit another signal.

• Any received signals from the receiver are then sent to a data recorder for storage on a disk or tape. later the data must be processed to be interpreted into something useful which would go on a display.

RADAR

Leader: Jhamaeca Pasamon

Janella Mae Abucay

Aviel Condalor

Sherilyn Diomampo

Emmanuel Layola

Mark Luis Opimo

WHAT IS RADAR?

• Radar is an acronym for Radio Detection and Ranging.

• It is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects.

Radio Wave

RADAR is a LIFE SAVER

Air traffic control and navigation radar:

9/11 ATTACK

Applications of Radar

Surface To Air Missile (SAM) - is a missile designed to be launched from the ground to destroy aircraft or other missiles.

Five Types for detection and search radar:

Air traffic control (ATC) - is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through controlled airspace, and can provide advisory services to aircraft in non-controlled airspace.

Early Warning Radar - is any radar system used primarily for the long-range detection of its targets.

AIRCRAFT SAFETY AND NAVIGATION

• Airborne weather avoidance radar outlines the regions of precipitation and dangerous wind shear.

• Low flying military aircrafts rely on terrain avoidance and terrain following radars to avoid collision with high terrain obstructions.

SHIP SAFETY

• Radar is found on ships and boats for collision avoidance and to observe navigation buoys, when the visibility is poor.

• Shore based radars are used for surveillance of harborers and river traffic.

MILITARY

• Important part of air defense system, operation of offensive missiles & other weapons.

• Target detection. Target tracking & weapon control.

• Tracks the target, directs the weapon to an intercept and assess the effectiveness of engagement.

• Also used in area, ground & air surveillance

REMOTE SENSING

• Weather observation - T.V. Reporting

• Planetary observation

• Below ground probing

• Mapping of sea ice

(September 11,2001)

(Four Russian Surface-to-air Missiles)

USES OF RADAR

Target Acquisition (TA) - Target acquisition is the detection, identification, and location of a target in sufficient detail to permit the effective employment of lethal and non-lethal means. The term is used for a broad area of applications.

Missile guidance system - refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its "Single Shot Kill Probability" (SSKP), which is part of combat survivability calculations associated with the salvo combat model.

Long range radar antenna

Marine and aviation radar systems can provide very useful navigation information in a variety of situations. When a vessel is within radar range of land or special radar aids to navigation, the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a chart.

SPACE

• Space vehicles have used radar for clocking and for landing on the moon.

• used for planetary exploration

• Ground based radars are used for detection and tracking of satellites and other space objects.

• Used for radio astronomy.

OTHER APPLICATION

• Used for non contact measurement of speed and distance.

• Used for oil and gas exploration

• Used to study movements of insect and birds.

Detection of aircraft

AIR TRAFFIC CONTROL

• Used to safely control air traffic in the vicinity of the airports and enroute.

• Ground vehicular traffic & aircraft taxing.

• Mapping of regions of rain in the vicinity of airports & weather.

LAW ENFORCEMENT & HIGHWAY SAFETY

• Radar speed meter are used by police for enforceing speed limits.

• it it used for warning of pending collision actuating air bag or warning of obstruction or people behind a vehicle or in the side blind zone.

(Counterfire Target Acquisition Radar)

(Titan Missile Guidance System)

RADAR SYSTEM - works by sending radio waves into the air, which are reflected back by the object and interpreted by a receiver. It has an almost unlimited range, since radio waves can be amplified using several mechanisms.

Primary Systems

• Receives echoes of the radio energy from its own transmitter , reflected back from a target, so it is the same frequency which is emitted and reflected.

Secondary Systems

• Transmits pulses on one frequency, but it receives pulses back to on a different frequency.

HISTORY OF RADAR

Christian Hülsmeyer (Huelsmeyer)

The Telemobiloscope was, however, the first patented device using radio waves for detecting the presence of distant objects. It could not directly measure distance to a target and thus does not merit this full distinction.

James Clerk Maxwell

• demonstrated that electric and magnetic fields travel through space as waves moving at the speed of light. Maxwell proposed that light is an undulation in the same medium that is the cause of electric and magnetic phenomena. The unification of light and electrical phenomena led to the prediction of the existence of radio waves.

Lucien Lévy

• the essence of the superheterodyne circuit is to convert a high-frequency signal to one of intermediate frequency by heterodyning it with an oscillation generated in the receiver. The intermediate frequency signal is then amplified before the detection and amplification that usually occurs in receivers. The superheterodyne circuit has the ability to boost weak signals significantly and makes it possible to reduce the size of antennas dramatically.

Heinrich Rudolf Hertz

• was a German physicist who first conclusively proved the existence of the electromagnetic waves theorized by James Clerk Maxwell's electromagnetic theory of light.

Albert Wallace Hull

• Hull's split-anode magnetron didn't prove to be capable of high frequency or high power output and was little used.

Lawrence A. "Pat" Hyland

• At the Naval Research Laboratory observed similar fading effects from a passing aircraft; this led to a patent application as well as a proposal for serious work at the NRL (Taylor and Young were then at this laboratory) on radio-echo signals from moving targets.

Albert Hoyt Taylor and Leo C. Young

• They were conducting communication experiments at the Aircraft Radio Laboratory when they noticed that a wooden ship in the Potomac River was interfering with their signals; in effect, they had demonstrated the first continuous wave (CW) interference detector.

Albert Hoyt Taylor

• Team had developed a practical shipboard radar that became known as CXAM radar - a technology very similar to that of Britain's Chain Home radar system.

George F. Metcalf and William C. Hahn

• they are both General Electric

• they develop the Klystron. This will be an important component in radar units as an amplifier or an oscillator tube.

• A klystron is a specialized electronic tube similar in concept to those used in microwave ovens. It will generate radar waves

RADAR