 Today, our topic is Antina Field Zone, Myself Piyusha Shedgarh. These are the learning outcomes. At the end of this session, students will be able to differentiate between the different field regions. They will be able to explain the concept of an isotropic antenna and they will be able to explain the various lobes of an antenna. These are the contents. Before going to start the basics of an antenna, you can recall what is the meaning of an antenna. So, you can pause video here for a second and recall that what is an antenna. Antina is a radiating device from which a power is radiated into free space, which is in the form of the electromagnetic energy. So, these are the different field zones related to the antenna. The field patterns generated by a radiating antenna which is varied with the distance and the associated width, radiating energy and the reactive energy. Whereas, whatever is the electromagnetic energy radiating into free space, the wave which having this energy is nothing but the radiating energy and the reactive energy is related to the complex quantity of the power. In the space surrounding of an antenna can be divided into the three different regions. First is the reactive field region, second radiating near field region and the radiating far field region. These field regions are separated by the boundary which are nothing but only the approximations. So, this figure shows the different boundaries with respect to the different field regions. The first field region is this is the near field region. Next is the radiating near field region and after that the far field region which are separated by this boundary defined with this R1, R2 and above that boundary R2 whatever is the region is nothing but the far field region. So, that means when the antenna is placed at the center which having the dimension is small d or it can be represented with the capital D. So, if the antenna is placed at the center the whatever is the radiating energy surrounding this antenna is can be differentiated with respect to different field regions. Now, what is the meaning of the reactive near field? The region where the fields are reactive that is the electric field and the magnetic fields are not perpendicular to each other that is these two are out of phase by 90 degree and for propagating or radiating the fields the fields must be orthogonal to each other. Now, the second region is the radiating near field region it is also known as a Fresnel region. The radiating near field region is the region between the reactive near and the far field. The reactive fields do not dominate in this region. Next, the third region is the far field region it is also known as a Fronoffer region. In this region a large distance is considered with respect to the antenna which is placed at the center. In this field the radiation pattern does not change its shape as the distance increases. Now, the near field region and the far field regions which are defined with the different radii which is denoted with the letter R1 and R2. So, R1 is given by this equation 0.62 times of under root d cube by lambda where d is the maximum dimension of the antenna and the lambda is the wavelength. Similarly, the radiating near field region which having the radius R2 which is defined by 2d square by lambda again the d is the maximum dimension of the antenna. Whereas, the lambda can be calculated by using this equation C0 by lambda where C0 is the speed of light and it is given by 3 into 10 raise to 8 meter per second. So, these R1 and R2 are not exactly the radii of the sphere these are nothing but the approximations these are considered the boundary between the different field regions. Now, how to calculate the R1 and R2 if you know the frequency and the d that is maximum dimension of the antenna. So, here we are considering one of the example with the frequency 3000 megahertz and the dimension of the antenna is the 0.1 meter. So, by using a bow equation you can calculate the radii for reactive region and the radiating region. So, by putting these values in the bow equation you are getting R1 and R2 for these two regions. Similarly, this figure can be shows the different field regions if the antenna is placed at this point and the near field region is denoted with this boundary denoted with the letter R it is given by 0.62 into d cube by lambda and raise it is this quantity is considered in the under root. Then the next frational region is given by 2 d cube by lambda and after this boundary the radiating far field is starting. Now, what is the isotropic radiation? So, for the reference antenna we are generally considering the isotropic radiation. Isotropic radiation is the radiation with consideration of the point source which is placed at the center. The radiating energy is radiated in all direction with the same intensity regardless of the direction of the measurement. And the improvement of the radiation pattern of an antenna is always considered with respect to the isotropic radiation of that antenna. That is the omnidirectional antenna which having the radiation in all directions. So, these type of the antennas are called as the isotropic radiation type of antenna. Now the point source is an example of the isotropic radiator. So, practically it is impossible to consider the isotropic radiation because every antenna radiates the energy electromagnetic energy with some directivity. The isotropic radiation is nothing but the omnidirectional radiation which having the Duffnut shaped pattern in 3D and figure of 8 pattern in 2D. So, this is the example of the isotropic radiation if the point source is placed at the center. Whatever are the magnetic radiation electromagnetic radiation in all directions shown by this orange arrows. Thus you can see the second figure the antenna radiates the energy in all directions. So, here the radii for this spare consider are the same. So, here whatever are the electromagnetic energy is placed on this surface is same with the equipotential field. Now, the related to the gain of the isotropic radiation the gain for this isotropic radiation is 1 in all directions. So, in terms of the decibel it becomes equal to 0 and the second is the equivalent isotropic radiated power. It is the amount of power that an isotropical antenna radiates to produce the peak power density observed in the direction of maximum antenna gain. So, what is the meaning of radiation? Radiation is nothing but the emission or the reception of wave front at the antenna specifying its strength. So, graphical representation of this radiating energy into the free space is denoted with the radiation pattern. So, from radiation pattern you can define the function and the directivity of an antenna. The power when radiated from the antenna has its effect in the near and the far field region. So, graphically it is represented with respect to angular position and the radial distance from the antenna. And generally the mathematical function of this radiation properties are considered with respect to the spherical coordinate system denoted with the electric field and the magnetic field with theta and phi. The radiation pattern can be the field pattern or the power pattern. The field pattern is the function of electric and magnetic field whereas, the power pattern is the square of the magnitude of the electric and magnetic fields. Now, what are the types of the radiation patterns? The radiation patterns can be plotted by the horizontal pattern and the vertical pattern. So, for a field the vertically polarized antenna the H plane is usually coincides with the horizontal azimuth plane. And for a horizontally polarized antenna the H plane is usually coincide with the vertical plane. So, this is the example of the vertical and horizontal polarization or the radiation pattern for that antenna. Now, what is the lobe formation? In the representation of a radiation pattern we get the different shapes according to the amount of the radiating energy. So, this is represented in terms of the radiation efficiency. So, there are the different lobes this denoted with the main lobe. These are the side lobes and this one are the back lobe. Now, what is the main lobe? The major part of the radiated field which covers a larger area is the main lobe or the major lobe. This is the portion where the maximum radiated energy exists. The direction of this lobe indicates the directivity of the antenna. Similarly, the side lobes are nothing but where the radiation is distributed sidewards. These are the areas where the power is vested. And the back lobe is the opposite of the main lobe is nothing but the back lobe. It is also known as the minor lobe, a considerable amount of energy is vested even here. Now, the different types of the patterns of the radiation of an antenna occur. One is the omnidirectional pattern. The pattern usually have a duffnut shape in three dimensional view and in two dimensional view the figure of eight pattern is known as the omnidirectional pattern. Second is the pencil beam pattern. The pencil beam has a sharp directional pencil shaped pattern, fan beam pattern which having the fan shaped pattern and shaped beam pattern the beam which is a non-uniform and pattern lace is known as shaped beam. These are the references for this session. Thank you.