 be taking a session on simulation software that is CST Microwave Studio where CST stands for Computer Simulation Technology. Basically this software is a modeling package for high frequency simulations. So let us start CST software, so to do that open CST Microwave Studio, so when you open this you will see two menus, one is file and other one is home. So file is a conventional menu where you can save the file with your selected name or you can open the previously made files or you can create a new project and here you can see other information related to licenses and projects, another option is home in this option you can create new project, you can see various windows, the windows which are shown over here is workspace, message window and progress window. So whatever is ticked over here those windows are displayed here. In this course firstly we will tell about the software interface then we will design a filter at 1 GHz on a substrate FR4 whose dielectric constant is 4.4 and thickness is 0.8 mm. So firstly just create a new project, to do that click on new and recent project then click on create project. So when you will create project you will see this window where you will find various sub-modules. So corresponding to this sub-module you can see various options, you can design these types of circuits. If you select this menu you can design PCB packages and other things similarly you can select various modules as per your requirement. So in this particular session we will be designing filters. So we will be selecting microwave, RF and optical modules and as we are designing filter. So we need to select circuit and components then click on next. In the next window we will see various sub-modules. Now I have already mentioned that we will be designing filters, so we will be selecting this filter, planar filter and if we want to design waveguide, cavity, couplers and other things then accordingly we will select the relevant module. So click on planar filter then go to the next option. Now you will see various solvers which it can use for its simulations. So there are frequency domain solver, time domain solvers and other than that few solvers are also there. So this time domain solver is used for broad frequency range whereas the frequency domain solver is more suitable for less frequency range. So here we want to see the simulation for broad frequency range therefore I would select time domain solver. So click on time domain solver then go to next. Then here we need to give preliminary settings like dimensions, frequency, time, temperature etc. Since I mentioned that we will be designing filter at 1 gigahertz so I will keep these dimensions as it is, I won't change anything and then click on the next. In the next section you need to define the frequency range for which you want to do the simulation. So here I will give the frequency from 0.5 gigahertz to 3.5 gigahertz. Then if you want to see the E field, H field or far field radiation pattern in between then you can define your monitors accordingly. So by default it takes the end frequencies and the center frequency. So when I clicked on E field, H field and far field you can see here the three monitors are defined which are corresponding to the end frequency and the center frequency. Now since I said that I am designing filter at 1 gigahertz so I will keep one monitor at 1 gigahertz and other monitor I will keep on the third harmonic that is 3 gigahertz. So then click next. Now it has created a template with some default name. So here you can rename as per your convenience. So right now I will just rename it as filter. You can see whatever template we have created the relevant information is given here. So the dimension is in mm, frequency is in gigahertz, time is in nanoseconds and the temperature is in kelvin whereas the frequency ranges from 0.5 to 3.5 gigahertz and the monitors are at 0.5 gigahertz, 1 gigahertz and 3 gigahertz. So we have defined the pre-liminary settings. Now finish this, when you finish this so it will create a temporary project file. You can see here various menus are there. So one is file menu, we have already explained about the file menu. The next one is modeling menu. In this the first option is import. So using this option you can import subprojects which were created in CST. You can also import various 3D models like set model, IGS model etc whatever options are given you can easily import these models to create the geometry. If you have made these geometry in any other software similarly you can import 2D models in the given format. Similarly if you want to export the models from CST you can export in set format, IGS format, step format and various models whichever is given here. And for 2D you can create Gerber files, GDS files etc. Next part is background. So background contains the background properties, here you can see by default background is normal. So if you want to change the background material from properties by defining the conductivity epsilon r mu r you can change the material. But here we want to keep the background material as air so we will not change anything. Next part is material library. So by default CST contains many materials that are predefined and their libraries are imported in CST. So you can see the list of materials which are already defined in CST, you can see here. Now suppose if you want to create a new library which is not given here you can make a new material library from here and then define epsilon r mu r conductivity and other things just to define the material library. Then next option is related to the geometries. Here you can see various predefined shapes are given. So you can easily make these shapes just click here then you double click and make the geometry. You can see wherever I click the mouse accordingly it took the dimensions and created the geometry corresponding to that. So this is the geometry which I have created. So this is a basic rectangular shape. If you want to make this sphere you can also make this sphere. Similarly if you want to make cone you can make cones. Similarly if you want to make toroid you can make toroid. If you want to make cylinder then you can make cylinder also just double click and then move your mouse in the height it will create the cylinder as per your requirement. So these are the predefined options there are some other options like extrude option to use extrude option you need to select a face. So to select the face just move to the right side here one option pick is given. In pick you can pick points you can pick edges you can pick faces and other things whatever is given here. So if I want to extrude it I need to select a face. So for example if I select this face and if I use extrude I can make a shape on this particular face by giving some height let us say 0.5. Now I want this to be twisted let us say maybe 60 degree and tapered by 70 degree and I can change the material if I want to change. So suppose if I change it to PEC I can change it here then press ok you see it has twisted as well as it is tapered. So by these options you can create various geometries. Suppose now if you are interested in some type of geometry which is not given here for that you need to use this option curve like for example you want to create a pentagon. So use this polygon option this then click on next then next again next point double click and then double click. So it has created a polygon but it contains only wire. You can see here these all geometries were 3D polygons. So corresponding to these polygons one solid is created over here you can see. However this is wire so related to this it is it is given in this curve. Now if you want to make a polygon using this for this you need to select this curve tool use extrude option extrude curve then double click on this and give a thickness for which you want to create a polygon suppose I will give here 0.5 maybe then it will create a polygon. So you can see corresponding to this one polygon has created which is solid 7. So in this way you can create a polygon of your desired shape. So these are the options now if you want to select a edge you need to select pick edge and then select the corresponding edge and double click. So in that way you will select the corresponding edge. Similarly if you want to select the middle point of a edge or the end points you can use the relevant options from here. Now if you want to clear this fix use this option this is the property option this gives the information about the objects which were created in the work space. So this is the work space where we create a full geometry. The next is history list. This option is very useful when we want to debug a particular geometry if there are some errors then this particular option is very useful to debug the errors which we have made. I will talk about this option little later. The next is calculator here you can give expression and it will give you the results maybe suppose if I take let us say 20 into 30. So then its product it will create and the result will be 600. So in the similar way you can give various expression and it will give you the value corresponding to that. Then next is the WCS WCS here by default in CST there are two types of coordinate system one is global coordinate system another one is local coordinate system. So this x, y, z is global coordinate system we cannot change this coordinate system. So if we want to change coordinate system to a particular location then we should use this local coordinate system. So in general I would suggest whenever you make your design you work using these local coordinate system ok. Now if you want to align these local coordinate system with edge or particular point you can do with these options easily. The next one is the cross sectional view. So if you want to cut and if you want to see at particular instant you can use this particular menu here in x plane you can see this it has shown you the cross sectional view of at x equals to minus 3 you can change the location similarly you can see it in y plane. And in the same way wherever you want to see you can see the next option is simulation. So first one is frequency. So if you have not defined the frequency earlier here you should mention the frequency. Next option is background. So in the background I have already told we will be using normal you can change here if you want to change it at later stage. Next is boundaries. So in our case we will be using boundaries so here you can use various type of boundaries like perfect electric wall, perfect magnetic wall, open edge space etc. So we will be using open edge space so I will make those changes in all the directions. Then these information is related to port. So in case of micro step we will be using the waveguide port and in case of wire antennas we will be using discrete port. The next part is lumped elements. So in lumped elements we can provide RLC components, diodes we can provide the specifications as per our requirement and correspondingly it will give you the simulated results. The next is field monitors. So if you want to define a field monitor for E field, H field, surface current or various options whichever is given here you can define it for a particular frequency point. The next is voltage monitor, current monitor. So you can apply all these monitors as per your requirement. The next is the transient solver which you have selected. The next option is optimizer. So by default it provides few optimization algorithm like you can see here CMA evaluation and this Trusted Region Framework. So these algorithms are used to optimize. If you want to optimize it for a particular function you can define that function over here. So these options if you want to explore you can use it. The next section is parameter sweep, I will talk about this little later. The next is log file which will show the results, again I will talk about this later. These options I have already explained, this one is mesh view which will show the meshed view of your structure. The next is global properties. So if you want finer meshing or maybe the mesh size of relatively more size then you can change these settings as per your requirements. But for the time being I will not change these things. Next section is intersection check. So if some polygons are overlapping with each other then this particular section, intersection check should be used. Another one is electrical connection. So this particular option is just to check the electrical connectivity between the polygons. So this particular window is for the post processing parameters like S parameters, gain, fire field and other things. So these are the options you can try from even template based processing. You can see you can select these options 2D fire field results, fire field and antenna properties, S parameters and all those things and accordingly you can do the processing. And last option is related to the structure view. You can view this, the structure or design in different ways by just rotating or by zoom in, zoom out or other things. You can see here in this option here you can see in windows you can select the window of your interest whatever you want to see. Suppose if I unclick this window you can see I cannot see this navigation window and if I click it it appears again. So I just want to tell you in this navigation window these options to this point these are related to the modeling of this structure and below this these are related to the post processing parameters which shows the results of the design. This one is a parameter list window. Here we define various parameters, here you can give the variable name and the values and we can define their type to remember at the later stage. The next is the message window which displays the various types of errors or alerts or warnings whatever comes in the simulation. Next part is a progress window which shows the status of the simulation when we run it whether it is completed or not. Let us start with the filter design. So as I mentioned that we will be designing filter on FR4 substrate. The resonance frequency of the filter let us take it as 1 GHz. Firstly to define a substrate go to modeling and we know substrate is basically a brick. Before this I would just suggest that whatever geometries we created just delete first all those geometries because those geometries were created to give you a reference that what type of geometries can be made using this particular interface. So press on brick then scrape then you can see here the local coordinate system is active. So in U direction let us take it as a length and in V take it as a width. So for length now I would just suggest all of you to define these lengths and widths in terms of variable parameters because here if you define it in terms of constant then at later stage if you want to change it it would be more time consuming because at every stage you will have to change it manually while if you define the variable you need to just simply replace in the variable it will automatically change. I will show you at the later stage. So let us just define it as L substrate may be L sub as variable name then the next is just keep this coordinate system is symmetric and then define it from 0 to W substrate and the thickness of the substrate let us take it H substrate. Now I will define these parameters L substrate I am taking may be 20 W 70 and then H we are using 0.8 mm thick substrate. Now here you can see the component is 1. You can change to another component and if you want to keep it in the same component you can keep in the same component and I want to rename the solid as substrate the material since I told you that we are using the FR-4 substrate. So we need to see whether we have FR-4 substrate in the library or not. So we need to just check it in the library just scroll it down to check it FR-4 lossy you see we have selected. This is the substrate we have defined now we need to make a ground plane on bottom side. So just select this phase and then use extrude option and name it as ground and give a height thickness as T for the copper and use T as 35 micron because when we get it fabricated in general 35 micron thick copper layer is printed and the substrate material should be perfect electric conductor for this case. So we have defined the ground plane and the substrate. Now we need to define the microstate. So to do that first start here and then align WCS ok then we want to maybe start from somewhere inside. So for that you can use transform use Y transfer and maybe just give this value as 10. Just see this geometry here. So this particular bottom strip is of 50 ohm impedance. So we need to find how much will be the width corresponding to 50 ohm impedance. However it is given here it is 1.5 mm but I will show you how to calculate using CST. So here if you check in home there is a option macros. You go to calculate then use calculate analytical line impedance. Then go to thin microstate option here various options are given. So you can calculate the various lengths and widths corresponding to various options like coaxial strip line and other things. So select thin microstate line give epsilon r 4.4 and the thickness we know it is 0.8. Now just check for W equals to 2 how much will be the impedance it is 42.48. Now we know W and Z are inversely proportional. So if we reduce the W my impedance will increase. So let us take maybe 1.5. So you see corresponding to 1.5 it is 50.82. So from here you can calculate the thickness of 50 ohm strip. Now we need to make 50 ohm strip. So to do that just name it as strip minus maybe take same as L substrate length L sub y2 as W. I am just giving the variables and I will put the value of these variables. The thickness of this copper you take is 35 micron again. So W 50 will be 1.5. So we have created the strip for 50 ohm line you see. Now we need to create the lambda by 4 strip. So to create the same again use strip and just name it as a strip maybe from let us take the width of the strip as 0.5 mm. So W strip maybe give variable name as W strip y2 from this. So let us take the width of the strip as W strip and accordingly define and L strip corresponding to lambda y4 using that same micro option it will come around 42 mm. So we will define the same let us take it 0.5 and then L strip 42 ok. Then we should define port. So to define port you need to select this phase then define port should be 3 into ratio of 50 ohm strip width and H substrate. In the similar way you define another port which is the side and then you start the simulation. It will take some time. So I just want to tell you that we have used the lambda y4 strip line and it is open at this end. So for the lambda y4 strip line we know that it inverts its behavior. So now if it is open it will act like a shot for the frequency for which it is lambda y4. So all the currents will go to this end. So corresponding to that frequency it will act like a band reject filter. So the response should act like a band reject filter. We will see the response. So in between as I was mentioning in the progress window we can see what is going on the progress in the message windows we can see various warnings and all those things. So in between we can see the simulation results from the S parameter window you can see here. The simulation is still going on it will take some minutes. Yes. So we selected W stub as 0.5. So this will be the response corresponding to 0.5. You see for S21 it is showing a notch which means that it is a band reject filter and S11 is very high. So it shows that at 1 GHz it acts as a band reject filter and at its third harmonic it will behave in the same way and while as if you see at 2 GHz that is up to twice of this frequency the length will be lambda by 2. So open will act like a open. So it should act like a band pass filter. So it is showing the same behavior as band pass filter should do. So this is how we saw that how this lambda by 4 direct coupled resonator will act like a band pass filter or band reject filter. So with this I would like to conclude. Today we discussed about the interface of CST microwave studio then we tried to design the band reject filter using FR4 substrate with thickness of 0.8 mm and with the lambda by 4 resonators. In the next lecture we will extend this and we will see how lambda by 4 resonator will act like a band pass filter and after that we will discuss about the design of power divider and hybrid coupler. Thank you very much.