 Good afternoon everyone. Our today's topic is Antina Types. Myself Piyusha Shedgarh. These are the learning outcomes for this session. At the end of this session, students will be able to explain short dipole antenna and half wave dipole antenna. They will be able to explain different elements of Yagi Uda antenna and its effect on radiation pattern. These are the contents. Now, before going to start actual types of the antenna, can you recall some basics of an antenna? So, you can recall it in terms of the multiple choice questions. So, consider here the first question is Antinas convert dash to dash. Options are given photons to electron, electrons to photons or both A and B or none of the above. So, you can think and you can write the answer. Yes, the answer is both A and B because the antenna is also known as the transducer which convert one form of energy into other form. Now, consider the basic requirement of the transmitting antennas R. It is low side lobes, last signal to noise ratio, high efficiency or none of the mentioned. Yes, the answer for this is the high efficiency. Antinas are of dash types. The antennas are two types, infinite types or none of the above. The antennas are having the infinite number of types. So, mention some of the types of the antennas are wire antennas, long periodic antennas, aperture antennas, micro strip antennas, reflector antennas, lanes antennas, traveling wave antennas. Last one is the array antennas. So, it is not possible to cover all types of the antennas in this session. So, in this session we will discuss about the wire antennas and traveling wave antennas. So, what is wire antennas? One of the most commonly used antennas are nothing but the wire antennas. They can be found in vehicles, ships, aircrafts, buildings, etc. Wire antennas come in different shapes and sizes like the straight wire. This straight wire is also known as the dipole loop and helix. Example of the wire antennas are short dipole antenna and half wave dipole antenna which we will cover in this session. Next type of the antenna is the traveling wave antenna. Antennas that have uniform pattern in current and voltage are nothing but the traveling wave. It is also known as non-resonant antennas. This can be achieved by properly terminating the antenna wire so that the reflections are minimized or completely eliminated to get the better efficiency. That is the standing wave does not exist along the length of the antenna. The wave is traveling. It will not standing or will not moving back and forth into the transmission media. Example for this traveling wave antenna is the Yagi Vooda antenna. Now consider the first type of the antenna, short dipole antenna. A short dipole antenna is a simple wire antenna. One of the end of it is open-ended and the other end is connected to the AC circuit. The frequency range for this type of antenna is around 3 kHz to 30 MHz. So this is most commonly used in low frequency receiver circuit. Now consider this is the figure of the short dipole antenna. One end is open-ended and the other end is connected to the AC source. So the electromagnetic energy is radiated from the open end through the free space. This is the length of the antenna. Short dipole antenna having the length of its wire shorter than the wavelength and therefore it is known as the short dipole antenna. A voltage source is connected at the one of the end of the antenna while the dipole shape is made. That is the lines are terminated at the other end. Now consider this is the figure which having the length antenna having the length is capital L. So here you can observe that the continuously moving wave which having the electromagnetic fields. So these two are the conducting plates the current flowing through these conducting plates. When the direction of the current changes the field is also varied. The wire that leads to the antenna must be less than one-tenth of the wavelength in case of the short dipole antenna. That is length is less than lambda by 10 where L is the length of the wire of the short dipole and lambda is the wavelength. Now what is the radiation pattern for this particular antenna? Dipole is vertical the pattern will be circular. The radiation pattern is a figure of eight pattern when viewed in two-dimensional figure. So consider the first figure is for the two-dimensional side view and here it is a top view of the antenna. So the pattern for this is the omni-directional pattern. Now what are the advantages of the short dipole antenna? Advantages of the short dipole antenna are ease of construction due to small size power dissipation efficiency is higher whereas the advantages are high resistive losses high power dissipation low signal to noise ratio radiation is low and not so efficient. What are the applications? Applications are used in narrow band applications used as an antenna for tuner circuit. Now if you are considering the long wire antenna these are found by the number of dipoles are connected to each other. The length of the wire in this type of antenna is N times of the lambda by 2 where N is the number of elements and the lambda is nothing but the wavelength and L is the length of the antenna. As N increases the directional properties of the antenna also increases. The length of the total wire used as a dipole equals half of the wavelength such type of the antennas are known as half wave dipole antennas. Also known as Hertz antenna. The frequency of its operation is half of its wavelength hence it is called as a half wave dipole antenna. So frequency range for this type of antennas are around 3 kilohertz to 300 gigahertz. It is a normal dipole antenna the edge of the dipole has maximum alternating voltage. At the positive peak of the voltage the electrons in one direction and in negative peak of the voltage the electrons tends to move in other direction. Now consider this is the figure of the half wave dipole antenna by assuming the positive pulse and the negative pulse. So figure 1 shows that when the dipole charges induced are in positive half cycle the electrons tend to move towards the charge. In figure 2 negative charges induced and therefore the electrons tend to move away from the dipole. Figure 3 shows that the dipole with the next positive half cycle the electrons again move towards the charge that is with the positive sign. Thus this process is continuous and this cumulative effect of wearing field effect which gets radiated in the same pattern produced on it. Hence the output would be an effective radiation. Thus you can say that half wave dipole radiates effectively. What is the radiation pattern for this type of antenna? So half wave dipole antenna is omnidirectional pattern as shown in this figure. What are the advantages of half wave dipole antenna? Input impedance is not sensitive matches well with transmission line impedance. It has reasonable length. Length of the antenna matches with size and directivity. And disadvantages of half wave dipole antennas are not much effective due to single element. It can work better only with a combination. Applications used in radio receivers used in telephone television receivers when employed with others used for wide variety of the applications. Now consider the Yagi Uda antenna. It is most commonly used type of the antennas for the TV reception. It is most popular antenna used in far decades. It is easy to use type of antenna with better performance. It having high gain and directivity. Yagi Uda antennas are used in the frequency range of around 30 mega hertz very high frequency and ultra high frequency bands. Now consider these two figures for the Yagi Uda antenna. Construction of this is nothing but it is a combination of parasitic elements and dipole. By taking these two you can form Yagi Uda antenna. So mainly the three elements of an Yagi Uda antennas are there. These are director feeder and reflector. Directors placed to increase the directivity of the antenna. The feeder is the folded dipole whereas the reflector is the lengthy element is used which is at the end of the structure. So the figure depicts that the clear form of an antenna. The center rod like structure on which the elements are mounted is called as a boom. The element to which a thick black head is connected is the driven element to which the transmission line is connected internally through the black stood. The single element present at the back of the driven element which is a reflector which reflects all the energy towards the direction of the radiation pattern. And the other element before the driven element are the directors which direct the beam towards the desired angle. Now this is the radiation pattern for the Yagi Uda antenna. The directional pattern for the Yagi Uda antenna is highly directive. The minor lobes are suppressed completely and the directivity of the major lobe can be increased by adding the number of directors to the antenna. Now what are the advantages of the Yagi Uda antenna? Advantages are high gain is achieved high directivity is achieved by using this antenna. Each of handling and maintenance less amount of power is wasted broader coverage of frequencies is covered in case of the Yagi Uda antenna. So what are the disadvantages? It is prone to noise prone to atmospheric effects applications these are mostly used for TV reception mostly used where a single frequency application is needed. These are the references for this session. Thank you.