ORGANIC LIGHT EMITTING DIODE [OLED] TECHNOLOGY

 OLED Technology:

Organic Light Emitting Diodes  are generally  solid state devices which is composed of thin films of organic molecules that are 100 to 500 nanometers thick. They are self emitting, like LEDS they do not require any backlight and filters. OLED emits light with the application of electricity.

Working of OLED Technology:

• Apply voltage across the anode and cathode.
• The generated current starts flowing from cathode to anode through the organic layers.
• Then from emissive layer of cathode electrons starts to flow.
• Leaving holes in the conductive layer electrons get removed.
• Those holes jump into emissive layer, finally electrons and hole combine and then light will be emitted with the application of electricity.

Features of OLED Technology:

• Flexibility
• Light weight
• Consume low power
• They are more efficient, much thinner and has wide viewing angle.

Applications of OLED :

• Televisions
• Computer Screens
• Mobile Screens 
• Keyboards
• Portable Device Displays

Pros of OLED:

• OLEDs are very thin and light to use. The display qualities are brighter than LEDs , thereby reducing power consumption.
• The light emitting layers are very light in order to make them more flexible.
• Provides a large viewing angle of 170 degrees.
• They maintain high consistency of speed.
• They are less resistive.
• OLEDs have a great picture quality with brilliant colours, infinite contrast and fast response rate.

Cons of OLED:

• The main drawback of OLED is, that they are only usable for limited lifespan.
• The displays of OLED are easily damaged by water, that leads to low adoption in display.
• Expensive manufacturing technologies.
• Limited market availability.

Conclusion:

The OLED will replace current LCD and LED technologies and evolve as the display for upcoming generations. When OLED technology reaches its peak, it will be better to improve certain existing limitations of LED and LCD.

SPACE COMMUNICATION

 Space Communication:

           Communication is more important to astronauts(or spacecraft) while they are in space because they have to communicate to their team who are in the ground so that they can complete their mission.

What is space communication?

            The Communications between vehicle or astronauts in outer space and Earth. Here the high frequency radio waves is used to communicate. Space communication depends on two things, the transmitter and the receiver.

Transmitter -  It encodes the message into electro magnetic waves.

Receiver - It collects electro magnetic wave and  decodes the message. 

Why we have to use high frequency waves?

          Because the space  communication is from million or  billion miles away ,the atmosphere acts to bend these rays and bounce them back towards earth, so that they can travel all over the world.

 Major reasons to use high frequency waves:

1. It gives greater pointing accuracy.
2. It minimises ionospheric effects.
3. It allows larger bandwidth(passes more information per unit of time).

How do astronauts communicate in space?

          We know that sound cannot travel through space(vacuum).So that the astronauts in space cannot communicate. But it is essential to communicate with the other crew members(other astronauts) and the team in the earth .Since radio waves propagate through vacuum , they fit devices in their helmets which converts sound waves into radio waves and transmit it to other astronauts or to the ground.

How do we receive and send signal to space?

          Spacecraft send information and pictures to earth using  Deep Space Network (DSN). DSN is the collection of big radio antenna from different parts of world. It is evenly spaced around the planet(as earth turns, it won't lost the sight of space craft). Spacecraft send images and other information to these big antennas. The antennas also receive details about where the spacecraft are and how they are doing. The DSN also sends list of instructions to the spacecraft. Once the data is received at DSN site, the data is processed and shared.

Role of amateur radio(HAM) in space communication:

          Amateur Radio on the International Space Station (ARISS) - operating in the Amateur-satellite service. Amateur radio operators all over the world are able to speak directly to astronauts through  their mobile or home radio stations. It is also possible to send digital data to the space station through same radio and antenna connected to laptop or computer.

TRAVELING WAVE ANTENNA

TRAVELING WAVE ANTENNA

              In radio and telecommunication, traveling wave antenna is a class of antenna that uses traveling wave on guiding structure as the main radiating mechanism.

                                           

DEFINITION :
            The antenna in which standing waves does not exist along the length of the antenna is called traveling wave antenna. It is a non- resonant  type ( aperiodic antenna) antenna which can be used over much broader frequencies.
     • It is a directional antenna in which traveling wave of electromagnetic oscillations is propagated along its geometric axis.
     • These antennas are made either with discrete radiators or in the form of continuous radiators.
     • Common types of traveling wave antenna are
           1. Beverage antenna
           2. Rhombic antenna
    •  This two types of antennas are used in transmitting and receiving installations for all            wavelengths of the radio band.

TYPES :
       In general, two types of traveling wave antenna are there
             1.SLOW WAVE STRUCTURE
             2.FAST WAVE STRUCTURE 

1.SLOW WAVE STRUCTURE :
            Slow wave structure is also known as the surface wave antenna where the phase velocity of the wave is smaller than the velocity of light in free space. The radiation for this type of antenna occurs typically from the feed and terminate regions.  There is an optimum length for this antenna depending upon the desired location of the main beam.

2.FAST WAVE STRUCTURE  :
            Fast wave structure is also known as the leaky wave antenna where the phase velocity of wave is greater than the velocity of light in free space. This structure radiates all its power within the fields in the direction of wave travels.

EXAMPLES OF TRAVELING WAVE ANTENNAS ARE :

      • The Helical antenna
      • The yagi-uda antenna
      • The spiral antenna

                            

Some of the linear wire antennas are the dominant type of traveling wave antenna. Recently, a new simple analytical and technical design of meanderline antenna has been developed which enables reduction of antenna length in traveling wave structure.

ADVANTAGES: 
     • This antennas are distinguished from other antennas by the presence of traveling wave and by the propagation of power in a single direction.
     • Since they are non- resonant type ,they often have wider bandwidth than the resonant antennas.
     • This antennas are simple and easy to construct.
     • Input impedance is high for this antenna.

APPLICATIONS :
    This antennas are used in various fields like
      • Commercial applications
      • RF communication
      • Microwave communication
      • Light aircraft
      • Military appliances
      • Long closed places like tunnels.