 Myself Rohini Mergo from doubletisulapur talking about the types of antennas. Learning outcomes at the end of this video you will be able to define antenna and its radiation mechanism. You will be able to list the different types of antennas. Let us first see what is an antenna. An antenna is a structure affiliated with the region of transition between the guided wave and free space wave. It acts as a transducer that converts the RF signal to electromagnetic wave. Antenna can be used for both transmission and reception of electromagnetic radiation. What is the need of antenna? Okay this is all about the antenna but do we really need antenna? What is the need of an antenna? So the antennas provide a simple way to transfer the signals or a data from where the other methods are impossible which are what I mean by this that I explain in the next bit. If I take the example of the airplane and if a pilot wants to connect with the ATC personnel air traffic control personnel and through the pilot is in the airplane and he is trying to communicate a message to ATC personnel. So in that case can you imagine that we are tying up some cable for transferring of the information or for sending some audio signal and sort of thing. So it is practically impossible or even if we imagine we feel it is like fuzzy thing isn't it? So it is not possible. So it is not possible to connect the cable to the tail of the plane and then we are communicating with the ATC personnel. So in that case there is no other option than wireless communication. Wireless communication is only the feasible option there. So antenna allows the propagation of electromagnetic waves from one end to another in the form of electromagnetic waves without need of wiring. This is very important without need of wiring system. So that is what the antennas are very important and need it. Now if I see the electromagnetic spectrum you can see here the different frequency bands which are specified by ITU International Telecommunication Union. So that as I shown is a low frequency band then you can see here high frequency band then you can see here the HF band. So this low frequency band is 300 kilohertz up to 300 kilohertz and HF band is up to 3 megahertz and then you can see high frequency band is from 3 megahertz to 30 megahertz and whereas the VHF very high frequency band is from 30 megahertz to 300 megahertz and UHF which is ultra high frequency band is 300 megahertz to 3 gigahertz and then it comes then the things goes on and likewise the different frequency bands which are specified by ITU as shown and based on that we can categorize the different antennas in different frequency bands. So let us look at the what are the different types of antennas. There are a number of numerous types of antennas are there. Those when I talk about indigival antenna indigival antenna has its own gain its own directivity and so on but there is one more type of the category of the antenna which is antenna array where we are stacking the similar or dissimilar antennas together to form an array. So due to this the antenna gain increases and its directivity also increases. So the antenna arrays are also again categorized as collinear array, planar array and phased array. So these are the categories of antenna arrays but even I can talk about the indigival antennas. Now here I have categorized as based on the frequencies. High frequency, very high frequency and UHF that is ultra high frequency antennas are wire antenna, rhombic antenna, multi-element dipole antenna. So the multi-element can be Yagi or log periodic or chord antenna, then helical antenna, slot antenna these are the different types of antenna which can work in UHF, VHF, UHF frequencies based on their design. Another category are shown is UHF and microwave antennas. In this category there comes a parabolic dish antenna, reflector antenna and horn antenna. Some special type of antennas are also there like spiral antenna, log periodic antenna why I am calling these as special because these are frequency independent antennas then reconfigurable antenna, smart antenna. What is this reconfigurable smart antenna? I explain in the video further and active antenna. So these are the categories of special antenna. First let us see the antenna array. An antenna when individually radiate an amount of energy in a particular direction for better transmission it would few it can would how it would be if we add more elements to it to produce more efficient output. That is more gain that is exactly the idea which led to the invention of antenna array. Here some diagrams are shown of antenna array this is a collinear array. So antenna is placed in a line it is a planar array so matrix sort of array is formed here. Here you can see phase array so the different antennas are provided the excitation and with the phase angle or phase difference sort of thing. So that is phase angle or different antennas have provided the excitation with the phase shifts particular phase shift HF and VHF and UHF antennas. HF is the high frequency as designated by ITU international telecommunion with a range of radio frequencies of electromagnetic waves between 3 to 30 megahertz. It is a decimeter band and decometer wave and having the wavelengths from 10 to 100 meters the next band or the higher frequencies are known as very high frequency that is VHF. VHF is frequency range is 3 to 300 megahertz where wavelengths are 10 meters to 1 meter. Frequences immediately VHF are denoted as high frequency HF and next higher frequency to VHF are called as UHF that means VHF is in between to HF and UHF. These are few antenna diagrams are shown here the pictures are shown of rhombic antenna it's a rhombus shape it's a rhombic antenna here helix or helical antenna here in the antenna the slot is there that is a slot antenna then UHF and microwave antennas is the next category where the frequencies next to VHF are known as UHF ultra high frequency and it is a frequency band designated by ITU that is international telecommunion is 300 megahertz to 3 gigahertz. So, microwaves is a form of electromagnetic radiation with the wavelengths ranging from 1 meter to 1 millimeter corresponding to the frequencies of 300 megahertz to 300 gigahertz respectively. The frequencies in microwave range are referred by IEEE radar band in the SCKUKA band as a designations given by IEEE for the microwave frequencies. So, few of the UHF and microwave antennas shown here are the parabolic dish antenna this is a reflector antenna this is the then horn antenna. So, some special antennas as I listed in that smart antenna was listed let me tell you what is smart antenna smart which is known as the adaptive array or digital antenna array or multiple antennas MIMO MIMO is multiple input multiple output and the antenna arrays with a smart signal processing that is why they are called as smart antennas. So, there is smart signal processing algorithms are used to identify the spatial signal signatures such as direction of arrival of the signal and use them to calculate the beam forming vectors which are used to track and locate the antenna beam when the target is moving for mobile target or for moving target. Another special antenna type is the reconfigurable antenna. So, smart antenna reconfigurable antenna smart antenna and reconfigurable antenna both the antennas done the some smart signal processing, but the difference is that the reconfigurable antennas have similar capabilities, but single element antennas. So, in the previous case where smart antenna I said there was antenna array processing, but here the single and element antenna processing. Then comes the category of active antenna which contains the active electronic components such as transistors as opposed to the antenna which only consist of passive elements such as metal rod capacitors inductors these are passive elements whereas active antenna allows the antennas of limited size to have wider frequency range they are providing wider frequency range because use of active elements such as transistors and those antennas are called as active antennas. So, the special antennas view I have shown here is a spiral antenna lock periodic antenna this is a smart antenna which is a phase array antenna which is shown here. So, I will be explaining spiral and lock periodic antenna in further videos. These are the references used for preparing this video. Thank you.