 Good morning everyone. Today we will see the topic Antina Parameters of Part 1, Myself Piyusha Shedkar. These are the learning outcomes for this session. At the end of this session students will be able to define the different parameters of an antenna and they will able to explain the different properties of an antenna. These are the contents for this session. Now let us define what is the antenna. Antina can be defined in different ways and antenna is a linking component of guided wave and free space. So if you are considering the source from the source when the electromagnetic waves are propagated and these are passing through the transmission media such as the waveguide it is considered as the guided wave. When this wave is radiated into free space then the antenna is considered as the important component between this guided wave and free space. Antina is a source or radiator of electromagnetic waves. Antina is a sensor of electromagnetic waves. It is also a transducer that is the transducer is it converts one form of energy into the other form of the energy is known as the transducer. Thus the antenna converts electromagnetic waves into the electrical signal or vice versa. That is the same antenna can be used as a transmitter as well as the receiver and therefore the antenna is also known as the duplexer. An antenna is used as a impedance matching device also that is for the effective efficient transmission of the signal there should be the matching of the impedance at both side that is at source side and the load side. Now before going to start the actual parameters of an antenna you can pause video here for two seconds and recall that what is radiation pattern of an antenna. So radiation is nothing but the emission or reception of a wave front at the antenna specifying its strength and graphical representation of this radiating field into the space is nothing but the radiation pattern of an antenna that is the wave radiated in which direction in which strength can be defined by this radiation pattern of an antenna. So from radiation pattern one can understand the function and directivity of an antenna. Now the properties of an antenna first property it has identical impedance when used for transmitting and receiving purposes. It has identical characteristics when it is used for transmitting and receiving purposes and the third property is it has same effective length when it is used for transmitting and receiving purposes. These are the different antenna parameters. There are the several parameters of an antenna some are listed here as a radiation pattern of an antenna power density intensity gain, directivity impedance, radiation resistance, effective length of antenna and antenna efficiency and effective area. So we will see it one by one. So first is the radiation pattern. So what is radiation pattern? It is nothing but the graphical representation of radiation as a function of space coordinates. So it can be termed in terms it can be termed as a radiation energy the field strength of an antenna radiated in a particular direction may be x, y or z direction. Thus the radiation pattern may also be in terms of the field strength at a given point. So these two figures shows the radiation example of the radiation pattern. In the first figure you can see that the red wave which is vertically polarized, the blue wave is horizontally polarized and this one is the circularly polarized. So in which direction the field is radiated can be defined with the polarization. So the electric field strength when perpendicular to the earth surface which is called as the vertically polarized wave whereas the electric field is parallel to the earth surface is known as the horizontal polarization and when the field strength is circularly polarized it is known as the circular polarization. So in second figure it shows linear polarization and the circular polarization in the same figure. So this is the example of the vertical polarization, this is the example of the left handed circular polarization. So the circular polarization polarized on the left side then it is known as the left hand side circularly polarization. When it polarized on the right hand of the wave then it is the right hand circularly polarized and again it is the vertical polarization. Now if the antenna is placed at the center of this x, y, z axis and for antenna radiation pattern we are considering the spherical coordinate system. As you know that the coordinates used in spherical coordinate system are r, theta and phi. So if you are considering the differential amount of this theta as a d theta differential amount of phi as a d phi and the differential amount is considered for the r as a dr. Then we can calculate the differential area for this portion as r square sin theta d theta and d phi. That is that if you are calculating the total area equal to integration of this differential area that is the integration is with respect to theta and phi coordinates. Again when the radiation pattern is drawn graphically the field strength is at the z axis. So which having this major lobe these are the side lobes and this is the back lobe. These are also known as the minor lobe because the values at this axis are the less as compared to this z axis and this is known as the major lobe. So the back lobe is exactly opposite to that of the front lobe. Here if you are calculating the beam width then consider the minus 3 dB of the max value at the major lobe and thus measure this angle as the beam width. Next is the radiation power density. The radiation power density is nothing but the quantity used to describe the power associated with an electromagnetic wave. It is defined with this consideration of pointing vector. So the pointing vector is defined as this electric field and the magnetic field which is the instantaneous value and these two are expressed in terms of hold per meter and the ampere per meter and the total radiated power is given by this equation thus you can consider it with respect to the differential area. So p is the instantaneous total power. This n cap is nothing but the unit vector normal to the given surface and dA is the differential area of the closed surface expressed in meter square. The average power radiated by an antenna is given as the radiated power is nothing but the average power. It is equal to half of integration with respect to surface and here we are considering the real part of the pointing vector. Next is the radiation intensity. So what is the radiation intensity? It is defined as power per unit solid angle. So this is the figure shows the radiation intensity. So this block is placed at a distance of r. This is placed at a twice of r. Then the solid angle is denoted with this D ohm. Now consider this is the sphere center and with the sphere which having the radius is r. Then one stradian defined as the solid angle with its vertex at the center of a sphere with radius r and it is sustained by spherical surface area equal to r square. And one stradian is defined with respect to the solid angle and one radian is respect to the plane angle. The number of stradian in the given sphere is equal to 4i. Since you know that the differential area for the spherical coordinate system is given by r square sin theta d theta d phi. Therefore the solid angle D ohm can be defined with this equation differential area upon r square. Thus the radiation intensity is denoted with the letter u. It is given by r square radiated in density. Therefore u equal to r square w rad and the total power can be defined as u that is the radiation intensity is different integrated with respect to solid angle. Whereas this angle is varied from 0 to pi for the theta coordinate and 0 to 2 pi for phi coordinate. Next is antenna gain. What is an antenna gain? It is defined as the ratio of maximum radiation intensity in a given direction to the maximum radiation intensity from a reference antenna produced in the same direction with the same power input. This is denoted with the letter g. G of theta phi is equal to 4 pi u of theta phi by P in that is the input power. This input power is given by the radiated power plus the loss of power. This loss is considered as ohmic and the dielectric power loss. Next is the power gain. Power gain compares the radiated power density of an actual antenna and that of the isotropic antenna on the basis of same total input power and at the same distance. So isotropic antenna is nothing but the radiation is in all direction. So gp is nothing but the power gain. It is defined with n into gd where gd is the directive gain and n is the efficiency which ranges from 0 to 1. So in the above equation when efficiency is considered as a 1 then the power gain becomes equal to the directive gain. Now the directivity. So what is directivity? It is defined as the ratio of maximum radiation intensity to the average radiation intensity. The average radiation intensity is nothing but the total power radiated by the antenna divided by 4. Thus the directivity of a non isotropic source is equal to the ratio of its radiation intensity in a given direction over that of an isotropic source. Thus the directivity is defined in terms of the dbi that is db reference to an isotropic antenna or dbd db reference to a half wave wavelength dipole. Directivity is the gain calculated assuming a lossless antenna. Directivity is related to the power radiated by antenna. Thus the directivity is defined again with respect to the two angles theta and phi. It is equal to u of theta phi by u0 is equal to 4 pi times of u of theta phi by radiated power. If the direction is not specified then the direction of the maximum radiation intensity is considered and thus therefore the maximum value of the directivity is denoted with the d0 equal to u by u0 where u is the radiation intensity and u0 is the radiation intensity of isotropic source. It is defined as u max by u0 where u max is the maximum radiation intensity expressed in Watt per study n whereas u0 is the radiation intensity of isotropic source. So, u max is considered with equation 4 pi times of the u max by radiated power. These are the references for this session. Thank you.