• Marine radars are used to measure the

bearing and distance of ships to prevent

collision with other ships, to navigate and to

fix their position at sea when within range

of shore or other fixed references such as

islands ,buoys , and lightships.

Brightness can indicate reflectivity as in

this 1960 weather radar image (of

Hurricane Abby). The radar's frequency,

pulse form, polarization, signal processing,

and antenna determine what it can

observe.

BASIC ELECTRONICSBASIC ELECTRONICS

TITLE: RADAR AND TITLE: RADAR AND ANTENNAANTENNA

• An object-detection system which uses electromagnetic waves specifically radio waves to determine the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, spacecraft

• 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.

What is radar?

• Light waves, radio waves, microwaves, radar waves is electromagnetic waves.

• Unlike water waves, electromagnetic waves do not require a medium such as water or air to travel through. They can travel through a complete vacuum.

• Similar to light waves, radar waves bounce off some objects and travel through others.

• The simplest mode of radar operation is determining how far away an object is. The radar unit sends radar waves out toward the target . The waves hit the target and are reflected back.

Basic radar operation

• The returning wave is received by the radar unit and the travel time is registered.

• According to basic principles of physics, distance is equal to the rate of travel (speed) multiplied by the time of travel.

• All electromagnetic waves travel at the same speed in a vacuum—the speed of light which is 186,282 miles (299,727 kilometers) per second. This speed is reduced by a small amount when the waves are traveling through air but this can be calculated.

How does radar work?

History of radar and Development

The USES of radar• Modern uses of radar are highly diverse

including• air traffic control, radar astronomy, air-

defense systems, antimissile systems like nautical radars to locate landmarks and other ships, aircraft anti-collision systems for ocean-surveillance systems, meteorological precipitation monitoring, altimetry and flight-control systems, guided-missile target-locating systems and ground-penetrating radar for geological observations.

• High tech radar systems are associated with digital signal processing and are capable of extracting objects from very high noise levels.

• ALTAIR - used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on Kwajalein Atoll.

» Israeli military radar is typical of the type of radar used for air traffic control. The antenna rotates at a steady rate, sweeping the local airspace with a narrow vertical fan-shaped beam, to detect aircraft at all altitudes.

• This Melbourne base Primary and secondary radar is used for air traffic control and to observe terminal area conflicts by VFR local aircraft.

WHAT IS ANTENNA?

An electrical device which converts electric current

into radio waves, and vice versa.

antenna

antenna

antenna

• Also contain reflective or directive elements or surfaces

not connected to the transmitter or receiver, such as parasitic

elements, parabolic reflectors or horns, which serve to direct the

radio waves into a beam or other desired radiation pattern.

THE HISTORY AND DEVELOPMENT OF

ANTENNA

Involved the coupling of electricity and magnetism and showed a definitive relationship was that done by Faraday somewhere around 1830s

Creating a time-varying magnetic field, which as a result (from Maxwell’s Equations)

First experiments

The coil acted as a loop antenna and received the electromagnetic radiation, which was received (detected) by the galvanometer-the work of antenna.

Built in 1888 by German physicist Heinrich Hertz in his pioneering experiments

To prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell

Developed a wireless communication system in which he forced an electrical spark to occur in the gap of a dipole antenna.

First antenna

He used a loop antenna as receiver, and observed a similar disturbance

This was 1886. Hertz placed dipole antennas at the focal point of parabolic reflector for both transmitting and receiving.

By 1901, Marconi was sending information across the Atlantic. For a transmit antenna, he used several vertical wires attached to the ground.

In 1901, Columbia University had an Experimental Wireless Station

There are several discovered antennas:

It is simple to construct and has a high gain, typically greater than 10dB

operate in the HF and UHF bands ( about 3MHz to 3GHz)

The Yagi antenna was invented in Japan done by Shintaro Uda

Presented for the first time in English by Yagi at America

Yagi-Uda Antenna (1920s)

At UHF (300 MHz-3GHz) and higher frequencies will achieved to 140 GHz.

Can range up to 25dB in some cases

Horn Antenna (1939)Horn Antenna (1939)

• Often called a ‘phased array’ is asset of 2 or more antennas

• The signals from the antennas are combined or processed in order to achieve improved performance

Antenna Arrays (1940s)

Commonly known as satellite dish antenna (30-40 dB is common) and low cross

polarizationHuge dishes( which can operate from 150

MHz to 1.5 GHz) Smaller dish antenna typically operate

between 2-28 GHzThe feed antenna is often a Horn antenna

with a circular aperture

Parabolic reflectors (late 1940)

Parabolic reflectors (late 1940)

• It printed directly onto a circuit board.

• low cost, have a low profile and are easily fabricated

Patch Antenna (1970s)

The quarter-wavelength Patch Antenna, which leads into the Planar Inverted-F antenna (PIFA).

The patch is shorted at the endHas the same current-voltage

distribution as a half-wave patch antenna

reduced in size 50%.

PIFA (1980)PIFA (1980)

THE USE OF ANTENNA

• Radio broadcasting A one-way wireless transmission

over radio wave intended to reach a wide audience.

The signal types can be either analog or digital audio.

• Broadcast television A mode of television

broadcasting which does not involve satellite transmission or cables which is typically using radio waves through transmitting and receiving antennas or television antenna aerials

• Two-way radio A radio that can

both transmit and receive (a transceiver), unlike a broadcast receiver which only receives content

• Communication receiver A type of radio receiver used as

a component of a radio communication link

• Cell phone A device which can make and receive

telephone calls over a radio link whilst moving around a wide geographic area.

It does so by connecting to a cellular network provided by a mobile network operator

• Satellite communication An artificial satellite stationed in

space for the purpose of telecommunication

They are also used for mobile applications such as communications to ships, vehicles, planes and hand-held terminals, and for TV and radio broadcasting, for which application of other technologies

• Wireless microphone  A microphone without a physical

cable connecting it directly to the sound recording or amplifying equipment with which it is associated

• Wireless computer network A wireless local area network (WLAN)

links two or more devices using some wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet

THE END….