ANTENNA & IT’S TYPES ‘Name = Mr-kadam Sachin Pandurang (B.Sci.(Blectronie scicnce)& M.Sci(Electronics seienee —Appear 2020).)What is Antenna ? + Antenna (or sometimes called as an Aerial), is that converts electric power imply radio an electrical devi into electromagnetic waves (or s waves) and vice-versa, + Asignal from a transmission line or the guiding device (hence the term guided wave) like a co- axial cable, is given to an antenna, which then converts the signal into electromagnetic energy to be transmitted through space (hence the term free space).Why do we need Antenna ™ There are several reasons as to why we need or why we use antennas, ‘but an important reason as to why we use antennas is that they provide a simple way to transfer signals (or data) where other methods are impossible. ™ For example, take the case of an Aeroplane. The pilot needs to, frequently communicate with the ATC personnel. If would not make any Acnse if we tie up a cable (of dynamically variable length) to the tail of the plane and connect it to the ATC ® Wireless communication is the only feasible option and Antennas are the gateway for that. There are many situations or applications where cables are preferred over wireless communication with antennas (like high speed ethernet or the connection between gaming console and the T.V., for example).Different Types Of Antenn Wire Antennas © Shot Dipole Antena ipole Antenna © Loop Antenna lonopole Antenna Periodie Antennas © Bow Tie Antennas = Log-Periodic Antennas = Lo Periodic Dipole Array ‘Aperture Antennas © Slot Antenna = Horn Antenna srostrip Antennas © Rectangulat Microstrip Patch Antenna © Quarter-Wave Patch Antenna ® Reflector Antennas plate Reflector / © Comer Reflector Antenna = Paral ia Reflector Antenna = Lens Antennas = Travelling-wave Antennas © Long Wire Antenna © Yagi-Uda Antenna © Helical Wire Antenna = Spiral Antena ™ Array Antennas ‘Two-Element Array Antenna inear Areay Antenna Phased Array Antennas1) A/2 Antenna {Dipole Antenna } © In radio and coions a dipole antenna or doublet is the simplest and most widely used elass of s The dipole is any one ofa chass of antennas producing a radiation pattern approximating that of an clementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end. ccommu This antenna introduce by German physicist Heinrich !ert first demonstrated the existence of radio waves in 1887 using what we naw know as a dipole antenna (with capacitive-end- / loading). A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods, The driving current from the is applied, or for receiving antennas the output signal to the receiver is taken, between the two halves of the antenna, Each side of the fede to the transmitter or receiver is connected to one of the conductors.Diagram and radiation patternAdvantages & Disadvantages of Dipole Antenna = Advantages :- = Balance:-Dipole antennas offer the advantage of receiving balanced signal enables the device to receive signals from a variety of frequencies. It also problems caused by conflicting signals without losing reception quality © Design Options :- In addition to the basic, television-top dipole antenna, many other forms ex Folded dipole antennas have ends that turn back toward the center to help maximize the signal strength. Other options include the half-wave dipole. the folded dipole and the half-wave folded te. The two-pole design Ips the device sort out Disadvantages :- Size :-Although the indoor dipole antennas are usually small, the outdoor versions ean be lange and difficult to manage. They often require more than one person to install, as the poles might be tall andl unwieldy, The size makes these outdoor-versions difficult to transport, move and install when niecessury, Moving It: If you'te using a small, TV-top dipole antenna, you must try multiple combinations of pole placements before finding the best reception position, Both poles typically rotate and extend, making ita hassle to move one and then the other continuously while seeking maximum reception.2) Horn Antenna ‘= Horn antenna coverts the electric power in to the radio waves and vice versa a radio transmitter or radio receiver it is usually used with © A hor antenna or microwave horn is an antenna that consist of a flaring metal waveguide shaped like a hom to direct radio waves ina beam © It provides a gradual transmission structure to match the impedance of'a tube to the impedance of firee space enabling the waves from the tube to radiate efficiently into space = Horns are widely used as antennas at UHF and microwave frequencies, above 300MHz, Signal sevangN cutAdvantages & Disadvantages Of Horn Antenna = Advantages of Horn Antenna: It is simple in construction, It delivers adequate directivity. = 1t offers bandwidth of about 10% Hor antenna along with parabolic reflector disc can deliver high gain. Disadvantages of Horn Antenna: = Horn antenna radiates energy in spherical wave front shape, as a result horn antenna does not provide sharp/directive beam. = Usually gain of horn amemna is limited to 20dB, Thi order to increase the gain when the horn opening is made la also becomes excessive. due to the fact that in ver, the length of hom3) Parabolic Dish Antenna © The parabolic reflector or dish antenna is the fornvof antenna which finds many uses in domestic satellite television reception, terrestrial microwave data links, general satellite communications and many more. @ |ts'size means that it is generally limited to use above jough larger antennas may be used for down to about 100MHz. © The parabolic reflector antenna or dish antenna is known high gain, and narrow beam Widths. It is the performance which can be-achieved by, using one is the reason itis so widely used at higher frequencies. © The standard definition of'a parabola is - Locus of a point, Which maves in stich a way that its distance from the fixed point (called focus) plus its distance from a straight line (called directrix) is constant. frequencHyperboloidal <— concave reflector ‘The-ahove figure shows the working model of cassegrain feed, Radiation Pattern Of Parabolic Dish Antenna © When the antenna acts as a transmitting antenna, the energy from the feed radiates through a horn antenna onto the hyperboloid concave reflector, which again reflects back on to the parabolic reflector. The signal gets reflected into the space from there. Hence, wastage of power is controlled and the directivity gets improved. ® When the same antenna is used for reception, the electromagnetic waves strike the reflector, gets reflected on to the concave hyperboloid and from there, it reaches to the feed. A wave guide horn antenna presents there to recei this signal and sends to the receiver circuitry for amplification.Advantages & Disadvantages Of parabolic dish Antenna Advantages Of Parabolic Reflector Antenna — Reduction of minor lobes Wastage of power is reduced Equivalent focal length is achieved Feed can be placed in any location, according to our convenience “Adjustment of beam (narrowing or widening) is done by adjusting the reflecting surfaces advantage Of A Parabolic Reflector Antenna — ‘Some of the power thut-gets reflected from the parabolic reflector is obstructed. This ‘becomes a problem with small dimension paraboloid. = applications of Parabolic reflector antenna ~ = The Cassegrain feed parabolic reflector is mainly used in satellite communications. © Also used in wireless telecommunication systems.4) Antenna array © An antenna array is a radiating system, which consists of individual radiators and elem Each of this radiator, while functionmg has its ‘own induction field. The etements are placed so closely that each one lies in the nei ‘one’s induction field. Therefore, the radiation pattem produced by them, would be the vector sum of the individual ones. The followin shows another example of an antenna array. The spacing between the elements and the | of the elements according to the waveleng also to be kept in mind while designing thes. amennias, © The anten ‘array. the ra form the radiation beam, which has high gain, high directivity and better performance, with minimum losses. individually and:w! 8 a in ation of all the elements sum up, toAdvantages Of Using Antenna Arrays ~ The signal strength increases High directivity is obtained Minor lobes are reduced much High Signal-to-noise ratio is achieved High gain is obtained Power wastage is reduced Better performance is obtained Disadvantages Of Array Anteam: Resistive losses Probability is increased Mounting and maintenance is difficult Huige extemal space is requiréd eoa0 Applications Of Array Antennas ~ Used in satellite communications Used in wireless communications Used in military radar communications Used in the astronomical study The Basic Types Of Arrays Are : ~ * Collinear array + Broad side array + End fire array + Parasitic array * Yagi - Uda array * Log- periodic array + Tumstile array + Super= turnstile arrayAPPLICATIONS OF DIFFERENT TYPES OF ANTENNA Aperture Antennas Reflector Antennas Micro strip Antennas Array Antennas Examples Dipole amenna, Monopole anvenna, Helix antenna, Loop antanna Waveguide (opening), Hom antenna Parabolic reflectors; Gores reflectors ‘Convexsplane, Goncave-plane, Convex-corvex, Coneavecaneave lenses (Cireviar-shaped, Rectangularshaped ‘metallic patch above the ground plane Yogl-Uda antenna, Miero stip paten array, Aperture array, Siotted wave (guioe array Applications Personal applications, buadings, ships, aulomeblies, space crams Flush-mounted applications, aircraft, ‘space craft ‘icrowave communication, sateite tracking, radio astronomy Used for very hightrequericy applications Ait-craf, space-craft, sateites, missiles, cars, moblle phones ete. Used for very high gain applications, mostly when needs to contro! the Fagiation pattem,