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TUTORIAL - Using CMU Mems Utility
Building A Folded Flexure Resonator Jan 28, 2000 |
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INTRODUCTION This tutorial explains the basic steps necassary to build a folded flexure resonator using the symbols and templates in the CMU Mems Utility. The resonator is a mechanical mass-spring-damper system consisting of a central shuttle mass that is suspended by two folded-beam flexures (one on each side of the shuttle mass). The resonator is driven in the preferred (vertical) direction by two electrostatic comb actuators (also called combdrives) one on the top and another at the bottom of the shuttle mass. The layout of the resonator is shown in Figure 1. |
Fig. 1 Layout |
The schematic of the resonator is shown in Figure 2. It consists of 5 plate masses (representing 1 central shuttle mass, 2 shuttle yoke masses, and 2 combdrive masses), 2 combdrive_y, and 2 folded flexures. Each folded flexure contains 7 beams, and 2 anchors. | |
Part I. Presteps 1. Start Cadence 2. Read schematic edit help to learn how to: A. Create a new library B. Create a new schematic cell view C. Placing an instance in a schematic editing window D. Some basic skills in manipulating the symbols E. List of required parameters for CMU Mems Utility components. 3. The schematic design of this tutorial can be found at: In the Library Manager, click "demo" in Library column, then click "resonator" in Cell column, then double click "schematic". 4. Create a new library "test". Create a new schematic in "test" library. Follow the steps to learn how to create a schematic like the one in the demo library. Feel free to refer to the demo as you go to compare with your own. Part II. Steps to build a folded flexure resonator 1. Lets start with the five "plate" instances. Place them in a horizontal row on the schematic. The placement of instances in the schematic does not matter but the pins must be wired up correcty. The middle one is the center shuttle; the second and fourth ones are the shuttle yoke; and the first one and fifth one are the mass of the combdrive. Connect them respectively. Edit the properties as follows: plate 1&5 plate 2&4 plate 3 unitl 5.5u 8.5u 26u unitw 106u 48u 13u unitnum_x 1 1 1 unitnum_y 1 1 1 percentage_holes 0 0 0 joint_offset 0u 3.5u 0u angle 0 0 0 2. Practice looking up properties in the demo schematic instances by selecting an instance then clicking the middle mouse button and selecting "Properties..." from the pop-up menu. 3. Now place the beams. There are 8 horizontal beams and 6 vertical beams. Note: you can rotate a beam by selecting the beam, clicking the middle mouse button and selecting "Rotate" from the pop-up menu. Enter all the necessary Properties. You will find the necassary properties for each beam on the demo resonator schematic. 4. Now place the comb drives. Note that the top one is "comb_1" and bottom one is "comb_2". The default comb drive is horizontal, so you have to rotate them. Comb drives have a lot of properties, be careful not to miss any! 5. Now place the anchors. Note that the anchor symbol can be rotated and flipped, but you have to keep in mind that "x" pins always connect to "x" pins, and the "y" pins always connect to "y" pins. You may see some demo connections that look very awkward because I didn't flip any anchors. This is just my personal habit. The Anchors have "length" and "width" properties. It will be helpful to zoom in closer to place the achors. 6. Place the the "layout_origin". Unlike the beams symbols that corresponds to physical parts on the silicon surface, this symbol doesn't have any physical counterpart. It is just an indication of the layout coordinate origin. This is the only symbol that does not have any property. 7. Check all your mechanical and electrical connections and save your file. A complete folded flexure resonator has been completed. Part III. Layout Generation Now that we've done all the hard work, layout generation is just a few clicks away. 1. In the schematic window, press F6. Notice there is a new menu item "Mems Utility" that appears on the top menu bar. 2. Click "Mems Utility". You will see three sub menu-items. 3. Click on "XC:YC for MEMS Schematics". You should see "New Values of XC, YC have been set up" in the CIW window. 5. Click on "Schematics => Layout". Part IV. Simulation and Analysis 1. After you saved your file, in the Schematic window click on "Tools" => "Artist". An Analog Artist Simulation window will appear. 2. Now we have to select the node we want to plot. In the Analog Artist Simulation Window, click on "Outputs" => "To Be Plotted => "Select On Schematic". Then in Schematic Window click on the electronic output net of the resonator. The net becomes high-lighted with color. (in the case yellow) 3. Now we are going to do an AC analysis to find out the resonate frequency. In the Analog Artist Simulation window, click "Analysis" => "Choose". A Choose Analysis window will appear. Select "ac", and set the frequency range as above. Then click "Ok". 4. In the Analog Artist Simulation window, click on "Simulation" => "Run". After Cadence finishes calculating a waveform window will appear. You can see that the resonate frequency is around 30k. If you got this far, congratulations! Your romantic journey with Cadence kicked off pretty well! Created 01/28/00 by khe@ece.cmu.edu |