 Myself, Piyusha Shedgar, Assistant Professor, Electronics and Telecommunication Engineering, Valchan Institute of Technology, Solapur. In today's session, we will discuss the slot antenna part 1. These are the learning outcomes for today's session. At the end of this session, students will be able to explain and draw the radiation pattern for slot antenna. They will be able to explain the working of slot antenna. These contents will be discussed in today's session. So, before going to start the slot antenna, you can pause video here for a second and recall that what is an aperture antenna? Yes, an antenna with an aperture or you can say the opening at the end can be termed as an aperture antenna. So, waveguide is considered as one of the example of aperture antenna. So, let us discuss the definition of the aperture antenna. The age of the ANE transmission line when and terminated with an opening at the end side which radiates the energy, this opening which is an aperture makes the aperture antenna. So, there are the main three types of the aperture antennas. First is waveguide antenna, horn antenna and slot antenna. So, let us define only the part of the first two antennas and we will discuss the slot antenna in detail in today's session. So, what is a waveguide antenna? A waveguide is capable of radiating energy when excited at one end and opened at the other end. This is nothing but the waveguide. Waveguide is used to pass the high frequency signals. The radiation in waveguide is greater than the two wire transmission line. So, the frequency range of the waveguide this type of the antennas around 300 mega hertz to 300 gigahertz that is this type of antennas works in the frequency range in ultra high frequency to extremely high frequency range. What is the meaning of this horn antenna? A horn antenna may be considered as a flared out waveguide by which the directivity is improved and the diffraction is reduced. The frequency range for the horn antenna is around 300 megahertz to 30 gigahertz. It works in the frequency range from ultra high frequency to super high frequency. Now, let us discuss about the slot antenna. The slot antenna is a radiator made by cutting a one half wavelength slot in a conducting sheet of metal or into the side or top of a waveguide. So, you can make a slot at the center in the sheet into the side or top of a waveguide. The slot antenna having the same characteristics as that of the standard dipole antenna it can be widely used on high speed aircraft applications. The frequency range of the slot antenna is around 300 megahertz to 30 gigahertz that is it works in the ultra high frequency to super high frequency range. So, this is how the structure of the slot antenna shown here at the side of this waveguide or the conducting sheet you can make a slot. So, this is suppose the center of the axis is considered for this metal sheet if this is nothing but the metal sheet and whenever the slot is cutting ease of length lambda by 2 then it gives you the slot antenna. So, you can make a slot at the side of this waveguide also. So, what is the operating principle for the slot antenna? So, whenever the high frequency field is present across the slot in the metallic sheet the energy is radiated. When a slot is cut from the surface of the conducting plate then on energizing the slot the electromagnetic wave is radiated thus it acts as an antenna. So, due to the presence of the slot at the center or in the waveguide it is named as the slot antenna. So, let us discuss the working of a slot antenna. So, generally the working of slot antenna depends upon the Babinitz principle. It having the rectangular conducting sheet over which horizontal or vertical slot is provided or cut which having the length is lambda by 2 and the breadth provided is suppose which is extremely very less than this length lambda by 2. This half wavelength slot resembles a half wave dipole according to the radiation and the gain properties of the antenna. So, slot antenna and half wave dipole antenna shows the variation according to the polarization. So, it follows the Babinitz principle. So, what is Babinitz principle? The Babinitz principle gives the relation between the slot antenna and the dipole antenna why because these two antennas are considered as the complement to each other. So, two complementary screens generate a similar diffraction pattern this is nothing but the Babinitz principle. So, according to this principle the structure of the slot antenna and the half wave dipole structure cut out from the conducting sheet are complement to each other. So, this is the figure you can consider this is the metal sheet which having the high conductivity. So, conductivity high means one can say the conductivity is the infinite. The slot is cut at the center of this metal sheet two wire transmission lines are connected here. So, the region in which the slot is cut from the conducting sheet is having the length is lambda by 2 is the half wave dipole that acts as a slots of complementary antenna. So, it is known as the complementary dipole antenna. So, slot antenna is also called as the complementary dipole antenna. So, this figure shows that this is a first figure is nothing but the slot antenna and the second figure is nothing but the complementary dipole antenna. So, here at the center the slot is cut and this is the metal sheet. In the second figure whatever is the slot length which having lambda by 2 length which having the metal sheet only and around this metal sheet there is nothing. So, that you can say that these two are complement to each other. Remember that this slot provided at the center of this metal sheet having the length is lambda by 2. So, it shows the relatability between the radiated field and the impedance of the slot antenna and the radiated field of the dipole antenna. Therefore, the complementary dipole antenna is nothing but the slot antenna. Now, this is how the radiation pattern for the slot antenna. So, if you observe the first figure and the second figure suppose this is the slot antenna radiation pattern and the dipole antenna radiation pattern. So, you know that the slot is having this portion of the length is lambda by 2. Same lambda by 2 portion is placed for the dipole antenna with the metal sheet. Here it is with the slot is provided. So, here you can observe that the electric field and the magnetic field are in the direction of the y and the x axis. So, here in the direction of the opposite of the y and the x axis. So, the magnetic field is in the direction of y axis whereas, in case of the slot antenna the electric field is in the y direction. So, whenever the slot antenna is horizontally placed then you are getting the vertical polarization and when the slot antenna is vertically placed then you are getting the horizontal polarization. But in case of the dipole antenna when the dipole antenna placed horizontally you are getting the horizontally polarization whereas, when the orientation of dipole antenna is vertical then vertically polarized signal is obtained. So, this is the main difference between the slot antenna and the dipole antenna. So, from this radiation pattern you can observe that these two are complement to each other. Now, this is the radiation pattern for the slot antenna. So, if you are observing the radiation pattern for the slot antenna is given in side view and the top view the radiation pattern for the slot antenna is roughly the omni-directional. So, the polarization of the slot antenna is linear. So, if you observe the top view of this it having the omni-directional pattern for the radiation of the slot antenna. So, if you compare the slot antenna and the dipole antenna these two are complement to each other. Not exactly practically it is possible to get all the parameters or all the characteristics are equal, but they are similar to each other. These are the references for today's session. Thank you.