 Hello everyone. In the last couple of lectures, we have talked about Microwave Theory and Technique course outline different books used. We talked about the Microwave Transmitter and Receiver Block Diagram. We also talked about Microwave components and it was followed by Link Budget. Today, let us just see what are the different systems we are going to cover in this particular course. So, let us start with something which you all people are used to your mobile phone. So, mobile phone actually speaking you can just see here a simple mobile phone, but in this particular simple mobile phone there are too many things are there. So, let us start from here. So, there is an antenna which is used for transmit as well as receive here. So, you are transmitting a signal and receiving a signal. So, now over here one can see there is a diplexer or filter because the transmitter and receive frequencies are different. So, over here you can see that this is the transmit chain and this is the receive chain. So, we had looked into the transmitter block diagram as well as receiver block diagram. So, you can see there are lot of similarities are there. So, you can say here there is a diplexer filter. So, which will only filter out the desired thing. So, it is also known as a double band band pass filter. So, one band is for this particular case and this is for the another one not this filter signal comes to the RF low noise amplifier. After that it goes to the mixer you can see here there is a local oscillator then it comes to IF amplifier there is a IF filter there is a demodulator. And so, you can see that this block diagram looks very similar to what I had shown you ok. Let us also look at the transmitter chain again. So, you can see that there is a modulator over here I will talk about these things little later modulator then there is an IF amplifier there is a mixer which does up conversion. So, this is slightly different than the block diagram which I had shown you, but otherwise you can see that all it is doing it is doing the up conversion. So, here modulation is done at lower frequency and then conversion is done to the higher frequency and this is the RF power amplifier. So, typically for a mobile phone this amplifier may give about roughly 1 watt of output power and in some system it may be even 2 watt output system then it goes through the filter and antenna. Now, what are these things over here? So, you can see here there is a microprocessor controller which actually has this all this human interface dialing memory battery power control and here is the data which you want to send which can be in the form of video data or speech. These things then go to because that may be a signal here could be you can say analog signal that is converted to the digital signal and then through the local oscillator some up conversion is done as I said this is done at a slightly lower frequency and then it is done at a higher frequency. So, this is what is a general block diagram. However, current mobile phones are much more complicated they have many many more things in there they also have a GPS receiver which is not shown over here. So, this is basically just to give you a general glimpse of the block diagram, but as I said the current mobile phones may have a GPS receiver they may have accelerator meter and so many things ok. So, now when there are too many mobile phones are there there is a requirement for jammer also. So, first of all what is a jammer? In fact, we also gave a name as silencer. So, what is a mobile phone jammer? Basically it generates noise which should be larger than the signal strength in that particular location. So, if the noise is larger then the signal received by the mobile phone will get confused and hence it will actually show that there is a no network available. Now, there can be different types of mobile phone jammer it can be a low power, medium power, high power basic purpose is a low power jammer will have a small range a high power jammer will have a larger range. So, it all depends upon whether you want to do jamming only in a small room or in a big hall or you want to even do a jamming at several you know concerts or even for you can say a military convoy they actually do a jamming for several hundreds of meter range also. Now, these jammers can be single band jammer or multi band jammer that means, either you are just jamming only one particular band or multiple band you are doing. The antennas can be two type omnidirectional antenna which will actually speaking omnidirectional antenna has a radiation pattern which radiates in this particular direction equally, but in the vertical direction radiation is not there it has a radiation pattern in this particular fashion which makes a figure of 8. So, when we talk about antenna will talk more about it. Directional antennas are antennas which send signal in a particular direction. So, where do we need to use mobile phone jammer there are lots of application. So, I will actually first start with the prison. Now, these days there are several jails where prisoners are actually able to smuggle in the mobile phones and then they do anti social activities even though they are in the prison. So, we need to install jammers in the prison. Now colleges many colleges these days are installing jammers specially during the exam time. I mean if you had seen a Munna Bhai MBBS movie in that movie one of the hero actually uses mobile phone for cheating purposes. In fact, that has created lot of problems. So, many colleges now have started installing jammers and also students are using mobile phones in the colleges. So, they are not concentrating on their studies and hence many colleges are also installing jammers. In meeting seminar rooms I mean your meeting is going on and somebody is mobile phone rings. So, of course, it is a nuisance. So, many times they install these jammers even in religious places let us say if you are going to some place to do R T and some mobile phone rings it is very annoying. Now VIP movement required jammer because these days many of the bombs are getting triggered by remotely mobile phone. So, even in the court and theater people have started installing jammer. So, jammers have lot of applications that way. Now this is signal enhancer and repeater. Signal enhancers and repeaters are basically nothing but the devices which amplify the weak signal in a given particular area. Now these signal enhancers again can be single band or multi band, it can have a gain or power, it can be low, medium, high depending upon in how much area you want to amplify the signal again it may have omni or directional antenna. So, what are the applications? So, I will actually start first in general that many hotels actually speaking have in building solution. So, in building solution consists of lot of power dividers couplers filters antennas and repeaters. So, that is how they are able to give signal in almost every possible room. But so, here any room or any hall wherever there is a no signal sometimes in the open space there is a possibility that signal may be V. Inside the lift you know that if it is specially a metallic lift you might have noticed that your mobile phone does not work and garage or parking lot specially underground parking lot signal is very very weak. So, they do install signal enhancers over there. GPS and GSM modules now GSM modules of course, are there inside the mobile phone even many mobile phones have GPS, but these nowadays these are separately available also. So, you can buy separately GPS module you can buy separately GSM module. In fact, nowadays even combined GPS and GSM modules are also available. So, GPS works at a frequency of 15 75 megahertz and the bandwidth is plus minus 10 megahertz. So, GPS can be used for many many application. So, for example, you can save GPS data in a memory and you can retrieve it later or you can transmit the data using GSM module or you can transmit using transceivers. There are several applications are there of course, these days people do car booking another thing also. So, which has a location finder. So, which actually has a GPS and other thing, but so in general you can use it for vehicle tracking, remote monitoring, location identification even some people use it for people tracking also. Now RF transceivers, what is a RF transceiver basically you can say mobile phone is an example of RF transceiver. So, RF transceiver consists of transmitter receiver. So, the combination of this is known as transceiver you can see that trans coming from here and this part is coming from here ok. So, by using RF transceiver one can transmit the data at a specified frequency. Now in India we have to use wireless planning commission and this comes under the umbrella of DOT which is department of telecommunication. In USA the corresponding body is FCC. Now in India RF transmitters transceivers are there 433 866 2.45 5.8, but I just want to mention here 433 megahertz band has not been approved in India, but almost you can say majority of the other countries do use 433 megahertz as transceiver, but this is not allowed in India as of now. Of course, when you are talking about transceiver what are the important things, what is the data rate at which you can transmit and what is the bandwidth allocated for that particular band. And of course, there are many applications are there you can use it for security purpose you can use for sending alarm or you can use for distress messaging and so on. RFID I am sure many of you are familiar with radio frequency identification might have use active or passive tag. So, you can just see here this is a passive tag over here you can see a simple one there is a this is one is a RF reader through the RF reader antenna is there. So, in this particular case we transmit the signal and what passive tag really implies that there is a no battery. So, what happens it gets the signal through this transmitted power and that signal is converted to DC voltage and then it sends back the signal and that is how the identification takes place. In case of active tag this may actually have its own battery. So, the advantage of having a battery is that the range is much larger. The disadvantages of course, you need a battery and the battery needs to be changed at different times. So, there are several frequencies which have been approved by WPC wireless planning commission in India. So, 125 kilohertz 13.56 megahertz 866 megahertz 2.45 gigahertz 5.8. So, you can really see there is a huge spectrum starting from kilohertz up to gigahertz. So, that is why there are lots of applications are there. So, it can be used in the retail it can be used for library management, vehicle license plate, e-passport, product tracking, animal tracking, electronic toll collection and so on. So, let us talk about ground penetrating radar. What is a ground penetrating radar in a very simple manner what we have here? This is a transmitting antenna which is sending the signal down and let us say there is an object and the wave gets reflected from this particular object and this is the receiver antenna. So, what it does here? This is used for buried objects it can be used for land mine detection, buried objects can be even it can be a gold it can be just buried copper cables or it can be a you know buried steel and so on. So, basically what the principle is that reflected amplitude and phase are captured for reconstruction of images for underground object. So, in fact, this you can even think about it is a part of microwave imaging also. So, how much is the depth one can go through that actually depends upon the depth of penetration depends on the transmitted power and frequency. So, just you give a general idea if the frequency is around 1 gigahertz the depth of penetration can be about 40 to 50 centimeter, but if you want a larger depth then you have to use lower frequencies. So, radar systems are of course, used for defense system. So, I am not talking about the defense system right now most of the time they are secret things. So, let us not talk about the secret things. So, what are the public domain things let us talk about that. So, these days radar systems are being used for many automobile application. So, we have some of these lower frequency region compared to this it is lower of course, otherwise 10 gigahertz or 24 gigahertz are very high frequency just to give you a little bit of a perspective most of the mobile phones work at 1 to 2 gigahertz Wi-Fi works at 2.45 gigahertz. So, 10 gigahertz is definitely larger than that, but now these 10 gigahertz or 24 gigahertz radar systems these are actually being used to measure speed of the vehicle. So, you might be familiar with the speed gun. So, basically speed guns are nothing, but used to monitor the speed of the vehicle and majority of the police would have these kind of a speedometer. So, that they can actually find out who is driving very fast and of course, then you may get a ticket. Of course, in India speedometers are not very popular, but abroad almost all the other countries do have police vehicles which are actually have these radars to measure the speed, but here I am talking about one additional application and that is to measure length of the vehicle. So, there are now these 10 gigahertz 24 gigahertz radar systems. So, not only they can measure the speed of the vehicle, they can also measure the length of the vehicle. So, in fact, we have worked on some of these system. So, where we could actually speaking what we did that we actually put this particular radar system next to the highway and we went early morning around 6 30 a.m. and we could actually see that you know when a Maruti car goes or a bigger car goes or a truck goes. So, you get actually a larger signature and with this particular thing then you can measure the speed as well as length of the vehicle. In fact, when we were doing the testing we found these to be extremely sensitive also and we can even detect hand movement also, but of course, the distance is up to only about 5 to 10 meter. Now these days of many automobiles especially high end automobiles and of course, driverless automobiles are using 77 gigahertz radar system and these are again now collision avoidance for the vehicle. And recently now all these things are also available in the module form. So, you can actually speaking by the module in fact, 77 gigahertz module is just approximately about 10 centimeter by 10 centimeter size. You can see it is really small and you can actually mount in the vehicle and majority of all these driverless vehicles do have that. As I mentioned some of the high end vehicles like high end mercedes they do have these kind of a high power radars. Then this is a again a becoming a very very important topic which is a RF energy harvesting system. So, why it is important? First of all I will tell you these days in the atmosphere we have too many RF signals, we have too many cell towers working at CDMA, GSM 900, 1800, then 3G, 4G, we have Wi-Fi modems almost everywhere these days. We have Wi-Fi enabled airports, Wi-Fi enabled colleges, Wi-Fi enabled railway stations. Now they are talking about Wi-Fi enabled cities. So, these signals are available almost everywhere. So, what is this RF energy harvesting system that you can use some of these available signal in the available in the environment or you can actually use this as a stand alone unit also. So, first of all let me just tell you quickly the block diagram. So, what RF energy system has it has an antenna then along with an antenna there is a matching circuit in between basically this circuit is required. What we generally need is an antenna should receive the signal and that should go to RF to DC conversion, but the rectifier input impedance is very different than the antenna impedance. Hence we need a lossless matching circuit and in this particular course we will talk about lot of different type of lossless matching network. So, this combination again part comes from rectifier and this part is coming from an antenna. So, that is how the term is rectina. So, this now RF to DC conversion we got a DC voltage over here that can go to the charging circuit which can charge a battery or it can be used for low power devices also. So, may not require for example, as I said RFID really speaking does not have any battery, but it actually uses straight way. In fact, RFID would not have any of these thing RFID at this particular point only it will go to the circuit which will send the signal. So, now we have designed this particular circuit. So, just to show you here one of the example. So, here we have actually designed a broadband monopole antenna why broadband? So, that we can receive the signal right from CDMA which starts around 800 megahertz up to Wi-Fi which is 2.5 gigahertz. So, we designed this broadband antenna and then this portion what you see over here that has actually RF to DC conversion as well as matching circuits all of that fits over here ok and you can see the size idea you can get there is a mobile phone over here. So, now just to give the demonstration here then a mobile phone starts ringing. So, we initiated a call from here this antenna received the signal and now you see what is the DC voltage measured by this that is 6.76 volt that is huge voltage which is sufficient to charge a battery. Now, just to tell you what we also did. So, we made multiple units of this. So, we put one unit on this side and we put another unit over here and we took this DC output of this and DC output of this and we put combined and over here we got more than 13 volt. So, that means, you can put one rectifier circuit here another retina or RF energy harvesting system and put a mobile phone. So, if you actually speaking put mobile phone in the speaker mode. So, while you are talking speaker mode you can use this voltage and you can even use this voltage to charge a battery. So, that would be a simple thing for mobile phone, but this particular thing can also be taken next to the cell tower and in fact, we have done some of these experiments also. So, when we talk about energy harvesting system we will talk about some of these things in more detail. Let us look at what are the different types of microwave equipment. So, we have a something like a microwave generator there are varieties of microwave generators are there. There are microwave generators may give output of only up to 1 gigahertz or up to 3 gigahertz or 10 gigahertz or 20 gigahertz of course, there are microwave generators at 100 gigahertz also. Then these microwave generators may have other features also they may have things like amplitude modulation built in a frequency modulation or it may have a digital modulation built into it. So, that you know when you get an output you can get a modulated signal output also. So, here in general microwave generator you can change the frequency from a low frequency value to a higher frequency low frequency can be in kilohertz also up to gigahertz and the output power also can be changed from a very small value which can be even let us say minus 100 dB to up to even plus 10 to plus 20 dBm also. Now then there is a spectrum analyzer basically spectrum analyzer is a equipment which measures the spectrum of a given signal. So, what you see over here that there is a signal is present over here and this is nothing, but a noise floor. So, again in spectrum analyzer majority of the time what you do you actually set the start frequency and the stop frequency and then you can see the spectrum of a given signal. So, then we have a network analyzer. So, basically network analyzer is used to measure the S parameters of a device ah S parameters also we will discuss in more detail, but just in a simple form suppose if this device is an amplifier. So, we connect the input over here we connect the output over here. So, you can actually measure the gain of the amplifier. Now if you have done a simple experiment in the analog circuits lab. So, what do you do you give a input signal through let us say a generator and then you measure this particular output signal let us say an oscilloso. So, generally speaking to get the frequency response measure. So, what you do let us say you want to do frequency response from 1 kilo Hertz to 20 kilo Hertz. So, you will give 1 kilo Hertz you measure there you give 2 kilo Hertz then measure the value then 3 then up to 20 and then you will sit down and plot the graph. Well network analyzer does all of those things in a very simple manner all you need to do it is you give the start frequency you give the end frequency you give the step frequency and then you connect this particular thing of course, before connecting you have to do one thing you have to do the calibration over here the calibrations are in the form of short circuit open circuit and match load. So, once you do this particular calibration network analyzer is ready to do the testing and you connect that and you will straight way get the plot you will get the plot of reflection coefficient also you will get the plot for transmission coefficient. So, what is reflection coefficient that will tell you what is the reflected power transmission coefficient will tell you what is the transmitted power. So, this can be used to let us say characterize a amplifier or let us say a filter or coupler or divider and so on and so forth. Now, let us look at various high power microwave system. So, of course, what you are familiar with the simple microwave oven. So, you can see a typical block diagram of a microwave oven. So, you can see here there is a power supply there is a transformer which goes to magnetron that magnetron generates a microwave frequency at 2.45 gigahertz through the waveguide it goes over here and that is actually going into the cavity where multiple reflections take place. Now, there may be a stirrer over here or there can be a turntable sometimes there may be both. So, that there is a uniform heating of the food which is kept in there, but however high power microwave systems are used also let us say communication ranges increase are just to tell you some of the defense system may even use 1 megawatt of power also and of course, microwave heating as I mentioned you may be familiar with the microwave oven, but there are many other applications are there it can be used for cooking it can be used for drying it can be used for food processing it can be even used for hyperthermia and of course, an extremely high power microwave can be used as microwave bomb alright. So, the what bomb does if this one actually basically microwave bomb transmits a very high power of small pulse which has actually a very wide bandwidth and this actually is used to destroy all the receivers. So, once a microwave bomb is put most of the receivers which actually work at a very low received power when they receive this very high power these receiver input signal get burnt. Now, microwave weapon is now reality where what they do they use high power microwave directed towards a certain segment and in fact, it has been now commercially used for crowd dispersal. So, you know that for crowd dispersal people do use tear gas or they use water cannon and here they have used high power microwave at millimeter wave frequency and by transmitting that people feel the burning sensation and they run away. Microwave imaging is now again becoming a very very important thing. So, here you can actually see that this person has concealed the gun inside the cloth, but just by looking at the image of that particular thing you can see that the gun is revealed. Now, microwave imaging can also be used in the medical thing. So, here is a one of the example where it can be used for breast cancer detection and there are many other applications are there. So, in conclusion I would like to mention that RF technology is rapidly changing lots of new advances are happening and specially now with the new two requirements which are coming up and that is 5G and IOT which full form is internet of things are just to tell you that 5G internet of things has been projected by the industry people as 7 trillion dollar market ok and just to tell you that as of now India's GDP is around 2 to 3 trillion dollar. So, you can imagine 7 trillion dollar is huge amount of money. So, there will be lots of things happening. So, I want to mention as far as India is concerned we miss the bus for 2G, 3G, 4G. So, all those things are getting imported in India. In fact, today India is one of the largest importer of let us say a apple phone. In fact, in India we have about 100 crore cell phone subscriber and only 10 crore cell phones are being manufactured in India. So, 90 crore or may be half of that 50 crore even if we say which are being imported and if you take an average price of 4000 rupees per mobile phone we are totally in you know we are importing about 2 lakh crore rupees worth of mobile phone and then all the infrastructure mobile phones and other thing are being imported. So, now 5G and internet of things if that is going to be let us say 7 trillion dollar market then Indian market itself may be touching 1 trillion dollar and that is like half to one third of the Indian economy. So, I think all the people, all the professors, all the researchers, all the industry people and students they should really seriously focus on microwave technology. So, that we should start designing in India and if we design in India then only we can make in India. So, make in India will be only successful if you do design in India. So, we really in fact, if these things are manufactured in India it will create lots of jobs in the manufacturing sector it will create lots of job in the design. So, all you engineers will get good possible job all you professors may get consultancy projects and all the engineers you have your hands full. So, I would like to mention that there is a requirement for innovating thinking to meet the demands and challenges and design is of course, the key thing and the design can be in two different segments. One thing is design would be which will be a low cost design. So, that would be very very important to compete with the rest of the world. The second thing is design could be that frontier technology you develop new technology. So, design can be from let us say low end to a very high end also. So, in this particular course we are going to look at different types of design and at different times I will tell you about what are the low cost design and where we need a high cost design especially when it comes to the defense and space application where performance is much more important and when we talk about commercial application then the cost is more important. So, we have to maintain a balance when we are doing the design of different component. So, now of course, in the next lecture I am going to first talk about microwave hazards because before you design anything whether it is a electronic product or whether let us say you are designing a bridge or the road you have to understand what are the safety requirements for that. So, in the next lectures I am going to talk about what are the health hazards possible because of the microwave radiation and what precautions need to be taken. Thank you very much. Bye.