 Good afternoon everyone. Today in this video we will discuss about one of the microwave component isolator, myself Piyusha Shedgar, assistant professor Valchand Institute of Technology, Solapur. These are the learning outcomes for this session. At the end of this session students will be able to explain the working of isolator. At the end of this session students will be able to explain different applications of isolator. These are the contents for this session. Before going to start actual topic isolator you can pause video here for a second and recall that what are ferrite devices. Yes the ferrites are non-metallic materials with high resistivity. They are a mixture of metallic and ferric oxide. So if you are taking the example of the metallic we are considering that MnO and the ferric oxide is nothing but the Fe2O3. So by mixing these two components we can find the ferrite components. In microwave devices ferrites find the application to reduce the reflection, the modulation purposes and in switching circuits. So wherever the high frequency is required that is more than 100 gigahertz applications ferrites are used because of the high resistivity property. Now what is isolator? An isolator is two port non-reciprocal device which produces a minimum attenuation to wave propagation in one direction and very high attenuation in opposite direction. So here the figure is given as a isolator which having the three ports port 1, 2 and 3 port. This third port is terminated thus it can be worked as a isolator so that isolator provides only the one way direction of the signal. If the input signal is applied to this port 1 you are getting the output at port 2 without any reflection towards the generator side. Again consider this is one of the example of the isolator. This isolator is having the two ports port 1 and 2 and if the circulator which having the three ports port A port B and port C the circulator can be worked as a isolator when the third port is terminated. When the third port that is C port is terminated it having only the two ports port A and port B. So it is the property of the isolator when the input is applied to this A port you are getting the output at port B with the reflection is equal to 0. Now consider the block diagram for the transmission system. So in several microwave generator circuit there will be the frequency and the amplitude variation at the generator load because of the reflection from the load side towards the generator side and the reflection from the load towards the generator will happen only when there is a mismatching of the impedance from the load to the generator side and therefore there may be the signal when transmitting from this microwave source towards the load due to mismatching of the impedance at the load side there will be some part of the reflection from this load towards the microwave source side. Thus there the system becomes unstable because of the variations at the generator side. Now if the isolator is placed between this generator and the load that is when the signal is applied from this generator towards the load side it will pass from this isolator towards the load side and if there any reflection from the load side due to mismatching of the impedance in load and the generator side whatever is the reflection is absorbed by this isolator. Now this is one of the block diagram of the isolator used in transmission system. So here the signal generator and the output side you can connect any type of a load and the third port is terminated. So here isolator maintains the one way direction of the signal flow. Now let us discuss about the construction of the isolator. Now this is the construction of the isolator. This is the rectangular wave guide which having the two ports port 1 and port 2. Near to port 1 the resistive card is placed when the plane of the wave of the propagation having the perpendicular plane to that of the resistive card then only the wave will pass through this resistive card. When the wave which having the plane of the polarization is parallel to the plane of that of resistive card then this wave is totally absorbed by this resistive card. This is the property of the resistive card. Another at the center of this rectangular wave guide Faraday's rotation ferrite rod is placed which is used to rotate the signal in clockwise direction by 45 degree. Again near to the port 2 another resistive card is placed which having the same property as that of the first resistive card. At the input side 45 degree twist is used for rectangular wave guide again this twist is in anticlockwise direction. Now let us discuss about the working of the isolator. In working of the isolator let us assume that T10 mode is applied to port 1. When the signal is applied to port 1 the signal is passed through this rectangular wave guide. When it comes to this resistive card the plane of the polarization of this T10 mode is perpendicular to the plane of the resistive card and therefore this wave is passing through this resistive card. When the wave out of this resistive card comes near to this 45 degree twist the wave is twisted by 45 degree in anticlockwise direction because of this 45 degree twist. Again when this wave is comes towards this 45 degree rotation because of this ferrite rod the wave is rotated by 45 degree in clockwise direction. Now this wave becomes perpendicular to the plane of the resistive card and that wave is passing towards this port 2. Now in this case whatever is the wave passing from this port 1 is obtained at port 2 without any reflection. Now consider that the input is applied to port 2. Now when the input is applied to this port 2 initially the plane of the polarization of the wave is perpendicular to the plane of the resistive card and therefore the wave is passing through this resistive card. When it comes to the center of the rectangular wave guide the wave is rotated by 45 degree in clockwise direction. Again when the wave passing through this near to this 45 degree twist is provided in rectangular wave guide. So therefore the wave is again twisted by 45 degree in clockwise direction. So here now the wave becomes parallel to the resistive card that is the plane of the obtained wave guide wave is becomes parallel to the plane of the resistive card and therefore whatever is the wave passing through this port 2 is totally absorbed in this resistive card and therefore no any wave is obtained at the port 1. So output at port 1 is equal to 0. Thus you can say that when the wave is applied to port 1 you are getting the same wave at the port 2 without any reflections and when the input is applied to port 2 at that time the output at port 1 is equal to 0. Now in practical session this is nothing but the microwave test bench practical setup. Here the power supply is used here you can generate the microwave signal which can be passed through this generator side towards the load side. At the load you can connect the CRO or VSWR meter. So whatever is the microwave signal pass from this transmission system transmitted signal is passing through this rectangular wave guide. So here this is nothing but the isolator. Isolator is used to provide a single path one way transmission of the signal from this generator towards the load side. So this is nothing but the variable attenuation. The attenuation of the signal can be changed by using this variable attenuator whereas this is nothing but the frequency meter is used to measure the frequency of the transmitted signal. This section is the slotted section. This slotted section is used to measure the VSWR and all the parameters of the microwave signal and through this rectangular wave guide whatever is the transmitted signal is received at this receiver side. These are the advantages of isolator. Isolator eliminates variation in source power output. It blocks reflection going towards the load. It avoids frequency pooling due to load changing. These are the different applications of the isolators. Isolator used in RF circuit design. Isolator used in test and measurement. Isolator used in RF chain as a component to prevent any undesired reflection. Isolator used in high voltage devices. It can be used in substation that is when a fault occurs in a substation then isolator cuts out the portion of a substation. Isolator used for the isolation purpose that is the input and output signals are isolated and therefore the reflection will be less. These are the references for this session.