4. Radar Wave
The word Radar was formed from the
first letters of the term Radio Detection
and Ranging .
Radar wave are actually Radio wave
It have frequencies as high as 300
GHz to as low as 3 kHz
Like all other electromagnetic waves,
they travel at the speed of light.
5. Antenna
Converts Electric Energy into
Radio Waves, and vice versa.
A Device for Sending or
Receiving Electromagnetic
Waves.
It is Usually Used with a Radio
transmitter or radio receiver
8. How does radar
work? Duplexer switches magnetron through to antenna.
Antenna acts as transmitter, sending narrow beam of radio waves through the air.
Radio waves hit enemy airplane and reflect back.
Antenna picks up reflected waves during a break between transmissions
Duplexer switches antenna through to receiver unit.
Computer in receiver unit processes reflected waves and draws them on a TV screen
10. RADAR Applications In 5 Arears
Military Applications:
• In air defense it is used for target detection,
target recognition and weapon control
•In missile system to guide the weapon.
•Identifying enemy locations in map.
Air Traffic Control:
•To control air traffic near airports. The Air
Surveillance RADAR is used to detect and display
the aircraft’s position in the airport terminals.
•To guide the aircraft to land in bad weather using
Precision Approach RADAR.
•To scan the airport surface for aircraft and ground
vehicle positions
11. RADAR can be used for observing weather or
observing planetary positions and monitoring
sea ice to ensure smooth route for ships.
Remote Sensing:
Ground Traffic Control:
RADAR can also be used by traffic police to determine
speed of the vehicle, controlling the movement of vehicles
by giving warnings about presence of other vehicles or any
other obstacles behind them.
Space:
To guide the space vehicle for
safe landing on moon
To observe the planetary
systems
To detect and track satellites
To monitor the meteors
13. UHF and VHF
Antennas
Ultra High Frequency /Very High Frequency
Receiving Antenna
Providers deployed voice and data
cellular
Spectrum used for land mobile system
Broadcasting fulfilled the demand
networks.
17. Advantages
RADAR can penetrate mediums such as clouds, fogs, mist and
snow
RADAR signal can penetrate insulators.
It can give the exact position of an object.
It can determine the velocity of a target.
It allows for 3D Imaging based on the various angles of return.
Cheap and fast method of calculating base maps when no
detailed survey is required.
18. Disadvantages
RADAR takes more time to lock on an object.
RADAR has a wider beam range (Over 50ft Diameter).
It cannot track if an object is decelerating at more the 1mph/s.
It cannot distinguish or resolve multiple targets.
It cannot resolve targets that are obstructed by a conducting material.
It is not very accurate.
Editor's Notes
Another application for antennas that I’m sure we’re all familiar with is VHF and UHF antennas, which stand for Very High Frequency and Ultra High Frequency. You’ve all seen the tall transmitting towers. They need to be large enough to achieve the desired frequency and provide a large range of coverage. VHF and UHF covers frequencies from 3 MHz to 3000 MHz and includes television and FM radio broadcasting.
The most common type of receiving antenna is called a Yagi array antenna. The array has different size conductors to receive different frequencies. Yagi arrays are highly directional, so they should always be pointed towards the transmitter tower.
There are obviously tons of applications for antennas, way more than I can cover. I’ll show some of the more interesting ones I found in my research.
The first is the United States Navy’s ELF system. ELF stands for Extremely Low Frequency. The Navy operates two antennas, one in Clam Lake, Wisconsin and the other in Republic, Michigan. The antennas work at 76 Hz, which if you used a half-wave dipole, the antenna would be over 1000 miles long. The ELF antennas are dipoles, but use about 80 miles of wire in the antenna. The reason for the low frequency is that the signal can penetrate seawater hundreds of feet to reach underwater submarines. Because the frequency is so low, the earth and the ionosphere behave like two conducting spherical shells. The signal travels around the world and reach submarines traveling at operational speeds. The one-way system is slow but reliable. The Navy submarines have ELF receivers which decode the message, but because of the large power requirements, subs cannot transmit ELF messages, so generally they will surface and use something faster like satellite communications.
Antennas have lots of applications in wireless communications. Many different types of antennas can be used, and they all have their own advantages. Two common antennas are the quarter wave helical and quarter wave whip antennas. The whip, which is the same as a monopole, is the most common antenna for cellular phones, and is typically used in the 400 to 500 MHz range. The quarter wave helical antenna is smaller than the whip and has similar performance. Lately it is used in the 800 to 1000 MHz bands. Another antenna you’ve probably seen is the retractable antenna. What I found interesting in my research is that there are actually two totally separate antennas that are electrically decoupled. In the extended position, this particular antenna functions as a whip and in the retracted position it works as a helical antenna. The performance is slightly better in the extended position.