Have you ever wondered how your mobile phones transmit and receive signals?Here come an antenna Antenna function by transmitting and receiving EM wave.For instance,sunlight is also a EM wave and the human eye that captures the light acts as an antenna.Em waves are launched into the space with the help of antenna It converts the electrical signal into EM waves and acts as an interface between electrical circuit and free space.
The first antenna were devised by German physiatrist Heinrich Hertz in 1888 .Antenna works by radiation mechanism.In the transmitter,the oscillating current applied to the antenna creates an oscillating electric field and magnetic field around antenna elements.The time varying fields radiate energy away from antenna into the space as a moving transverse EM wave.In the receiving section,the incident EM exists force on the electrons in antenna causing them to move back and forth creating oscillating current.
The characterization of antenna is determined by desired frequency,gain,bandwidth, polarization and impedance matching.In the earlier days Antenna size and shape determines the operating frequency.Later oscillator regulates the antenna frequency.Single wire or rod and parabolic dishes can act as an antenna.A single antenna can act both as a transmitter and receiver.
An antenna radiates energy equally well in all horizontal directions is called omnidirectional.An antenna radiates in a particular direction is called directional antenna.
SOME ANTENNAS AND ITS APPLICATIONS:.
1)YAGI UDA ANTENNA: It is widely used in receiving tv signals.It is also used in the fields of radars,satellite and RFID application.
2)LOG PERIODIC DIPOLE ANTENNA. It is used to monitor the solar bursts.
3)DIPOLE ANTENNA: It is mostly used in radio communications.
4)TRAVELLING WAVE ANTENNA: It is using in satellite communication.
5) ANTENNAS PRESENT IN MOBILE PHONES :There are multiple antennas on each phone.They are primary cellular antenna(transmit and receive ),Diversity cellular antenna(receive),GPS.
ANTENNAS BEFORE 4 G
1 st generation wireless cellular technology mainly based on analog.The first generation network was launched in USA. Later 2G networks follow digital communication in GSM and it supports SMS and MMS .3G supports GPS ,mobile tv,video conferencing.Majority of them use external antennas such as helix ,monopole,helix plus whip combination.
ANTENNAS AFTER 4G
4G supports high speed applications,mobile tv and wearables.PIFA antenna is used here.In 5G,high data speed,reduced latency ,energy savings are essential.Millimeter wave microstrip antenna is used.As the mobile communication evolves antenna design varies because of different operating frequency .
INTERESTING FACT ABOUT ANTENNA:
In 1913, Eiffel tower was used as an antenna ,the only condition is that the antenna had to be very large to get any sort of radiation.The Eiffel tower fit well and was used to communicate with the United States Naval Observatory in Airlington
HOW TOUCH SCREEN WORKS!
Touch screen is an electronic visual display unit which acts as a human machine interface. It enables the user to control the digital world inside the device.Input is given by means of touching the display with the finger.The input is detected and the required informations are processed by the appropriate hardware and software and displays the required content over the display.Unlike mouse and keyboard,touch screen allows user to interact with device directly to touch the images on the screen.
Touch screen technology was first developed in 1960 for air traffic control systems and is now a popular user interfacing technology on devices ranging from ATMs, supermarkets, Airports and smartphones.
There is a variety of touch screen technology and each has a unique detecting methods. Electricity,light are used for detecting according to technology.They are Resistive,capacitive and surface wave technology.
RESISTIVE: The screen is coated with electrically conductive and resistive layers. It consists of top (resistive) and bottom (conductive) transparent sheets facing each other with a gap between them.The two sheets are coated with Indium Tin oxide.The gap is filled with tiny dots called spacers to keep the two layers apart until you touch.The uniform electric current is flowing through the two sheets.when we touch the screen both the layers are pressed together and the current is changing at the point of contact. The change in current is recognised by the appropriate software and the required task is implemented.
CAPACITIVE: The capacitive touch screen is coated with a material that stores electric charges.Uniform electric field is distributed over the panel.when the panel is touched uniform current flow is disturbed at the point.circuits at the screen corners measure the change in current flow and send the information to the controller for processing.There are two types of capacitive technology:surface capacitive and projected capacitive technology.
SURFACE WAVE TECHNOLOGY: In the surface wave technology the ultrasonic waves are passing over the touch screen panel. Transmitting and receiving transducer,reflector are used. Waves are generated by the transmitting transducer and it is reflected by the reflector at the edge of the screen and received by the receiving transducer. When the panel is touched, change in ultrasonic wave is detected at the point and it is recognised by the controller.
The tough screen technology shrinks the digital world at your fingertips!!!
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