 Hello everyone, this is Dr. Rupali Sherke from Valchin Institute of Technology, Sholapur working as an associate professor in electronic department. In this video lecture, we are going to introduce a radar system. The learning outcomes of this lectures are after completion of this session students are able to illustrate the concepts and the technologies used in a radar systems. The contents which will be covered in this lectures are introduction to radar, radar frequency bands, advantage and limitations of the radar, applications of the radar, simple radar systems, what are the requirements in the radar systems and classifications of the radar system. This will be an introductory lecture. Before starting with the radar system, let us think what is what could be the frequencies which are used for the radar system. Radar system is working in the range of microwave frequencies, what is a radar exactly? What it stands for? A radar stands for radio detection and ranging, it detects the signals or a target by transmitting the electromagnetic signals and determine the range of that target, that is why it stands for as it is transmitting the radio signals that is the electromagnetic view to detect the target and also it detects the range at what range the target is being located, that is why it is called as a radio detection and ranging. Now, the basically the radar concepts was the bird bat in which the eco signals are been received based on that concept, this radar concept is been developed. Radar is nothing but we also called as it is gathering the information about the distinct object or a target by sending the electromagnetic waves at them and analyzing the reflected wave which are in a form of eco signals. In this diagram, we see that a transmitter station transmit the signals at the target whose range has to be determined or the target has to detect and the received signals which are in a form of the eco signal. The reflected signals are the eco signal, some reflected signals will be act as a wave signals. This is how the basic concepts of radar works out. The transmitter and the receiver are placed at the same location if we also in this figure. The radar can detect the statistic as well as the mobile object that is a moving object. The parameters by which can be determined by using in this radar system is you can detect the range of the target, you can detect the angle at what angle location it is being placed and if it is a moving target then you can also determine the velocity at which the target is being moving. This is a these are the parameters which can be measured or a detected by using the radar system. So, initially the radar was developed from 1990s after a world war II. What is a frequency band? We know that in a microwave frequency we are using, but what is a frequency band because of microwave frequency is also too vast in that what are the frequency bands which are standardized for the radar systems. They are the frequency ranging from 1 gigahertz to 40 gigahertz are been initially assigned for the radar system by the ITU standards. After that these signals are again the divided into the different bands of which are basically used for the radar applications like L, S, C, X, Q, K and K bands. These are the standard bands of exactly which these bands been using and this is the frequency range which are specified into the gigahertz. Now what are the advantage and limitation? Let us discuss on them. The advantage of the using the radar system, the radar can see through the darkness, haze, fog, rain and snow as they are the electromagnetic waves are in a gigahertz frequency they can transmit for a longer distance. So, they can travels through the different layers of the atmosphere also. They can determine the and the range and angle of the target as which you are already discussed previously. What could be the limitations of using this radar? As for every advantage there is a disadvantage the limitations or demerits of the radar system is this radar cannot resolve like a human eye. What we can immediately determine what exactly the target whether the target is aeroplane or target is a shape we can determine by our naked eyes, but the similarly the radar cannot be detect the exactly the look this what exactly the target is being placed, but it can determine the range and the angle of that particular target and also it cannot resolve the colour of the target. These are the disadvantage of the radar system. Let us discuss with the applications of the radar systems basically a radar system is been applied into two areas that is civilization areas and a military areas as for the security purpose or we require for the military purpose also. In the civilization applications they are been used for navigating areas on the ground and sea to detect the ranges to see the on the sea levels we are using the for the navigation purpose. The radar altimeters is used to detect the height and height of the plane about the ground. To determine the height we are also using the radar elimator. Airborne radars are used for the satellite surveillance. Police radars are for the detecting and directing the speed of the vehicles. Radar for determining the speed of the moving target like in a cricket we can determine the speed of the balls which is thrown by the baller during the in a military application we can determine the speed of the atomoballs which is being emitted from the rifle also shells also a guided missiles we can also determine the speed of the guided missiles in a in a civilized application. In a military applications we can use the for detecting and ranging of the enemy target even in the night as on the border side we can we are using the radar system for detecting the even in the night because they can transmit the signals during into the darkness. The aiming of the guns at the aircraft and ships bombing ships aircraft of cities even through the overcast at the night early warning regarding the approaching of the aircraft or a ship at the airport or at the stations as well as detecting the guided missiles also searching of the submarines and the land mass these are the peaks of the radar systems. Now, let us discuss with the how this radar system is being a basically radar system consists of a transmitter and the receiver the transmitter and the receiver both are been connected to the duplexer circuit. The duplexer circuit is connected to the antenna initially a transmitter and receiver were using the separate antenna to transmit and receive the signals but nowadays a duplexer is used to connect the single antenna to connect the transmitter and receiver a transmitter transmit the signal through the duplexer towards the target and the eco signals are received and received towards the receiver which are being displayed on the radar display. There are different types of the radar displays which we will be discussing in the next lectures. The basic requirement what should be this what are the requirements of the radar system is that the duplexer which we are using it should be automatically operated and the radar transmitter should be in a silent during the when it is receiving the signal. Now, as we know that for transmitting we require a high power if you use the same antenna for the transmitting and receiving that is why while receiving the signals in the signal strength is less that while transmitting the signal strength is high that there is a possibility that the receiver may damage during the transmission. To analyze this or to protect the receiver the power transmission pulses should be quite powerful to encounter the attenuation during its forward and return journey. The received eco signals being weak that is why the receiver should be highly sensitive and time we mentioned to the noise signal. Radar antenna which is being used for transmitting a ratio they should be highly directive or large should have a large gain. The duration of the pulses which are called as a pulse repetitive frequency which are being transmitted to and as well as to distribute they are are are nothing but they should be high as compared to the target scanning period. The PRF is given by the duty cycle per width pulse width which is in the range of 0.1 to 10 microseconds. So, the average power is a product of the depends on the power transmitted and the duty cycle that is transmitted power into the pulse width into the PRF. The details of this we will be discussing in the next topic while we are discussing with the radar range equation. The classifications of radar are in the two types pulse radar systems and continuous which is also called as a Doppler radar. In a pulse radar system the pulse wave or a train of the narrow rectangular shape pulses which are modulated by the sine wave as a carrier signals are being transmitted from the transmitter. The only difference is in the types of the transmitted signals. In a pulse radar signal the signals are transmitted in a form of pulses. The pulses duration this is a on type this is a off time of the pulses and the range of the pulses is determined by the 2 and 4. It is transmitting duration distance r and receiving duration 2 that is why in a two way that is why it is measured the total distance measured is 2 r. In a continuous radar the signals are transmitted in a form of continuous signals and the received signals we apply the Doppler effects for that. The Doppler effect is nothing but a change in the wavelength of the signals. If you observe in this figure this ambulance is as it is moving towards this observer 2 that is why the frequency is high in this for this observer 2. But while as this ambulance is moving away from the observer 1 the frequency is reduced to the observer 1. This principle is being used in a radar communication. These are the few references in which through which we are discussing these topics. Thank you.