 Hello everyone, myself Piyusha Shedgarh in today's session will discuss the topic antenna array. These are the learning outcomes. At the end of this session students will be able to define an antenna array, they will be able to identify the need of an antenna array. These are the contents. So before going to start an antenna array, you can pause video here for a second and recall the two important parameters of an antenna that is directivity and gain. Yes, directivity is defined as the ratio of maximum radiation intensity to the average radiation intensity and gain on the antenna is defined as the ratio of intensity of radiation in a specified direction to the average radiation intensity. Let us discuss the basics of an antenna array. What is an antenna array? Array is an assembly of antenna elements arranged in an orderly fashion. These elements are usually identical. You can consider these elements are non-identical, but forgetting the proper radiation of the signal. You can consider these are usually identical elements. Antenna array is used to increase the directivity and gain. How form the antenna array will be formed? Antenna formed by multiple elements is known as antenna array. It is a group of similar or dissimilar elements each with its own amplitude and phase relation arranged in certain configuration to produce certain desired radiation characteristics. What is the need of an antenna array? If a single element is used in antennas, what are the disadvantages we are getting which can be overcome by using antenna array is discussed here. With the single element, we are getting the wide beam of the signal which gives you the lower value of the directivity. By using single element, it may be increase in size and therefore it becomes bulky. It be difficult to build a single antenna system with the single element and it becomes expensive. With the single element, it is useful especially when the element gain is low. But instead of using single element, if you are using the multiple element in antenna system, it is used to increase the gain of an antenna. It is also having a narrow beam by using the multiple elements. Single element antenna can be used to increase the size of an antenna for large distance communication. It is also used to get the higher directivity and the lower side loops can be observed with multiple elements. In an array of identical elements, in general five control points are to be considered to shape the overall pattern of the antenna. So one of the point is the geometrical configuration. So geometrical configuration may be considered as the linear or the circular polarization, etcetera. Relative displacement between the elements is to be considered. Again, the excitation amplitude of the individual element is to be considered along with the phase of the individual elements. For getting the overall pattern of the antenna proper, you can consider the excitation amplitude along with the excitation phase. And the fifth point is nothing but the relative pattern of the individual element. Now, this figure shows the antenna array. So it is one of the single element as an antenna element. Then if you are increasing the number of elements, so if you observe this figure, the same element can be used. So these all elements are the identical elements and these are connected through the wire to each other. So thus, the multiple number of elements are connected together to form an antenna array. Second figure and the third figure is also shows with the same antenna array. Antenna array can be defined with the two types. First is single dimensional array and the second one is the two dimensional array. How to define the single dimensional array? If an array arranged on a single axis that is on may be x axis, y axis or the z axis, then it is said to be a single dimensional array or it is also known as the linear array. This is just a single dimensional array because the array elements are arranged on either x, y or z axis. But if you are taking the combination of the two axis, then the two dimensional array can be formed. So if an array arranged in a plane, either xy plane, yz plane or you can consider the xz plane also, then it is said to be two dimensional array. Or it is also known as a planar array. So this is the figure for the two dimensional array z axis. This is the y axis and this is nothing but the x axis. So the number of elements are placed on this x axis along with this x axis and again along with the y axis. And by taking the combination of these x and y axis, the number of elements are connected to each other and thus the array is formed. Each element on x axis are separated by the distance dx whereas on the y axis, each element is separated by the distance dy. That is here the number of elements are placed along this or on xy plane and thus the two dimensional array can be formed. So this figure shows the array elements with the individual amplitude along with the phase control points. So it is the single element that is this is the first element, second element like that you can use the number of n number of elements. Amplitude for the first element is denoted with the a0 point whereas the phase shift for the first element is given by this psi 0 notation. For the second element, the amplitude is a1 and the phase shift for that particular element is denoted with the psi 1. So that you can consider the individual amplitude and the phase shift for each element for getting the overall pattern for the antenna array system. So an-1 is considered as the amplitude for the nth element whereas the phase shift for that element is given by psi n-1. So here the number of elements can be connected to each other to form antenna array. So spacing between the elements and the length of the elements according to the wavelength are to be kept in mind while designing this type of the antenna array system. The antennas radiate individually while in array the radiation of all the elements are summing together to form the radiation beam which has the high gain, high directivity and better performance with the minimum losses will be possible because of just antenna array. What are the different advantages of antenna array? By using antenna array the signal strength can be increases, higher directivity can be achieved by using antenna array. antenna lobes are reduced much better as compared to the single element. Highest signal to noise ratio is also possible to achieve by using antenna array. High gain is also obtained. Power wastage is reduced this is one of the advantage for antenna array with the better performance is obtained. Let us discuss some disadvantages of antenna array. Losses are increased because of the antenna array. Mounting and maintenance becomes somewhat difficult because of the number of elements can be used. Huge external space is required to mount this type of the antenna array system. What are the applications of antenna array? It is used in satellite communication, it is also used in wireless communication, used in military radar communications. Also used in astronomical study. These are the references used for today's session.