Today our topic is antenna communication system and it is very important part of communication system so to understand telecommunication technology we must know antenna and its working principle so that we can better understand about telecommunication technology in previous post we have already studies basic communication system you can refer previous post
Antenna is an important part of wireless communication systems like mobile, TV remote, computer, car remote or many other devices which communicate wireless as you see from above figure the voice signal our sound wave is converted into the electrical signal by microphone and this electrical signal again converted into electromagnetic wave by transmitting antenna and transmitted in the space or air and other side same receiving antenna which receive electromagnetic wave signal and this electromagnetic wave signal again converted into sound wave by loudspeaker which our ear drum detect and we listen the sound signal but you can ask or want to know how electromagnetic wave is created by antenna this is important point to understand lets see.
How electromagnetic wave is created
This demonstration was done by Hertz scientist before Hertz Maxwell predicted about electromagnetic waves that due to undulation of electric and magnetic field electromagnetic waves is created Maxwell also told by accelerating a charged particle electromagnetic wave can be created now it was turn for Hertz to prove the statement given by Maxwell.
Hertz got the meaning statement accelerating a charged particle means same as oscillating a charged particle hence Hertz taken a LC oscillator as shown below.
As from above picture LC Oscillator here L is Load and C is capacitor when a charged capacitor is connected with load inductor as we know capacitor has two plate one is positively charge other is negatively charge as load connected now positive charges start to move from high potential positive plate to low potential negative plate and due to charge movement current start flow in the circuit through load inductor as current passes through load inductor magnetic field start to developed in inductor and as capacitor fully discharged then current flow is stopped in the circuit at this time magnetic field is maximum in inductor now due to current stopped now magnetic field start slowly vanish and hence due to change in magnetic field in inductor an EMF is induced now current start to flow in opposite direction as shown in figure 2 and now capacitor is again getting charged due to current flow in opposite direction and this process continue hence it is an oscillator charges are moving back and forth we suppose that this is undamped oscillation means energy is not loss the energy stored in capacitor is transfer to inductor same amount of energy when capacitor get discharged and again same amount of energy transfer from inductor to capacitor this type of oscillation is called undamped oscillation means energy is conserved.
Now refer figure 3 here positive and negative polarity is continuously changing hence charge is oscillating back and forth hence using electrical signal electric and magnetic field undulation create an electromagnetic wave electric and magnetic field are perpendicular to each other two poles shown positive and negative is a dipole antenna one pole will be in positive state then other pole will be in negative state so it is called dipole and its one specific feature you must know the antenna will create electromagnetic wave or detect electromagnetic wave antenna minimum length will be ?/2 where ? is wavelength of electromagnetic wave similarly mono pole antenna is there where only one pole is used which radiate in all direction its condition is ?/4 for length of antenna hence this was the basic concepts about antenna in next post we will continue communication topic i hope that you have enjoyed learning Antenna communication system thanks for reading and sharing this post.
dated 21st Sep 2018