University of California, Berkeley Spring 2007 EECS 117 Prof. A. Niknejad Experiment by Ehsan Adabi EECS 117A Demonstration 4 HFSS Simulation of a Transmission Line Getting started : • Microsoft Start > Programs > Ansoft > HFSS9 • After program initialization, click on the blue icon for ( Insert HFSS Design ) • Select the menu item HFSS>Solution Type , choose Driven Terminal click OK • Select the menu item 3D Modeler>Units , choose mm and click OK • Select the menu item 3D Modeler>Grid Plane > XZ Draw the Structure : • Select the menu item Draw > Box • Using the coordinate entry field on the bottom right of the page enter the position: X : 0.5 , Y : 0 , Z : 0.5 press enter and then at the same place enter dX : -1 , dY : 10 , dZ : -1 • Select the menu item View > Fit All > Active view • In the vertical column next to the drawing field under the objects right click on Box1 > Edit > COPY and again right click on that Edit > Paste ( Now you have Box1 and Box2 with the same size on top of each other and you need one of them later on to make a hole ) • Similar to Box1 create Box3 with (X:1,Y:0,Z:1) and (dX:-2,dY:10,dZ:-2) • Similar to Box2 create Box4 with the same size of Box3 and on top of it • Similar to Box1 create Box5 with (X:1.5,Y:0,Z:1.5) and (dX:-3,dY:10,dZ:-3) • On the object column click on Box5 press Ctrl key and also click on Box4 ( you selected both Box5 and Box4) then go to 3D Modeler > Boolean > Subtract and then subtract Box4 from Box5 (Blank part : Box5 , Toll part : Box4 ) • Do the same thing and subtract Box2 from Box3 • Now you are left with three boxes : 1,3,5 you can click on their names on object menu and there will be a property window on the left side of the page and you can change the names Box1>inner_cond , Box2>dielectric , Box3>Outer_cond you should also change the materials assigned to them as following Inner_cond > Copper Dielectric > Rogers RT duroid 5880(tm) [ with permittivity of 2.2 ] Outer_cond > Copper Also the Solve Inside Boxes should be checked for all of them. If you don’t check that for the metals you are not going to capture the conductive losses.• Now the layout so far should like like this : Creating the Wave Port Excitations : • Draw a rectangle (Draw > Rectangle) with ( X:1.5,Y:0,Z:1.5 ) and (dX:-3,dY:0,dZ:-3) your grid plane should be XZ to be able to draw that • Select it, right click on it and choose Assign Excitation > Wave Port then click next choose 1 for number of terminals and select new line for the integrationline, now you have to choose two points for that line and these two points are the outer of inner_cond and inner of outer_cond. Once finished, you should have something like the figure in the next page. You can use Zoom and rotate icons on the top-right of the page • Similarly draw port2 at ( X:1.5,Y:10,Z:1.5 ) and (dX:-3,dY:0,dZ:-3) Analysis: • HFSS > Analysis Setup > Add Solution Setup In the General view : Frequency = 10GHz Maximum number of passes = 10 Maximum Delta S = 0.01 In the Option view : Minimum number of passes = 2 Minimum converged passes=2 Click OK • HFSS > Analysis Setup > Add SweepDiscrete type of sweep from 0.2GHz to 10GHz with the step of 0.2GHz • Check the validity by HFSS>Validation Check and if there is no error go ahead and run the simulation HFSS > Analyze All . Wait a few minutes for the simulation to be done . Results : • HFSS>Results>Solution Data> Matrix Data • Then choose Z Matrix , Real-Imaginary. Z11 is the impedance seen by port1 when port 2 is open circuited so it should be capacitive at low frequency. From the data calculate the capacitance at low frequency and express the capacitance per unit length in fF/mm. What’s the Q of that capacitor? Similarly see the Y Matrix and since the 1/Y11 is impedance seen by port1 when port2 is short circuited. Calculate the inductance, inductance per unit length (pH/mm) and the Q of that inductance. • Also check the Zo and see if it’s equal to sqrt(L/C)? • Plot the input impedance for an open and short circuit line over frequency by HFSS> Results > Create Report> Im or Re ( Z11 or 1/Y11 ) and find at which frequency the line could be used as a resonator? • Find the propagation constant of the line. What is the Q of the line in resonance? • Find the quality factor of the resonator by sweeping the magnitude of impedance of a short line and observing the 3dB