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Home > Examples > Small and Large Signal Simulation of RF PIN Switch Small and Large Signal Simulation of RF PIN Switch  § To start designing this device, first click on Model § Go to the Options drop down menu, select Units, and set your length to Microns. § Then, in the Options drop down menu, select Settings. § Make sure you have a metal at the bottom of your substrate by selecting Yes for Metal at Bottom, and set your Frequency Range from 1 to 200GHz, then press OK. § You can make all your necessary changes to Dx, Dy, and Dz in the Control Panel. Keep in mind, however, that these values need to be lower than the Max value posted above (with Max being a function of the dielectric constant, the frequency range, and the mesh density). Set Dx=15, Dy=33.3, Dz=10. (Tip: for faster simulations Dx, Dy and Dz may be set as close as possible to MAX, which can be achieved by increasing/decreasing the maximum frequency range in the Options-Settings) § In the Domain Properties panel on your right, set your epr to 12.9. § Go to Chip Designer by clicking on the icon § Click on the Edit drop down menu and select Change Grid Dimensions. Set the dimensions to 43x30. § To start editing your metal design shape, first click on the Draw Rectangle icon o Using your mouse to click, drag and resize your shapes, or just clicking on the metal shape and using your arrow keys to position it. o Or you can just click on the desired shape, and manually enter its exact dimensions and location in the Properties panel located on the right. To get out of Edit Mode, simply click on the  (Hint: Make use of the coordinates bar located at the bottom of the Metal Design screen to help with your design process):  § You Metal Design should look like this so far:  § You can now add the other identical rectangle, by simply duplicating this shape. To do so, go to Edit Mode, click on the shape you wish to duplicate, and either click on the duplicate icon   § You will now need to add the horizontal bar with the following dimensions: and the design will be turned to:   You can duplicate it to add the other one and have your metal design look like this: 
 Your final metal design should look like this:  Now that you have your metal designed, click on  § To finalize your design, you will now need to add a Pin Diode between your bridge and the horizontal metal bar in the middle.
Please not that you could use any other component, depending on your technology. o First, click on the Pin Diode symbol  o Then you will need to specify what 2 metals it is connecting to. You can set that up in the Component Properties Panel on your right:  The Pin Diode will automatically shift vertically. You can then set its exact location and press Esc on your keyboard when you are done.  § You can now manually set your specific component’s properties in the Components Properties panel on the right. Both of OFF and ON state of Pin Diode with small signal simulation would be considered here.
1. OFF state
§ Before running the Simulation, make sure to insert ports on both sides of your Switch. When you are ready, click on the Simulation button · When the Simulation is complete, click on
2. ON state
Next, Let's check the second case when Pin Diode is ON by keeping the other parameters the same. Following the similar steps, you can view the S-parameter plots as follows: The results show that the RF switch doesn't performs very well when the Pin Diode is ON state. It has been proven that the performance can be enhanced by adding the via between the metals and ground plane.
§ In order to do that, enter chip designer by clicking icon . Click icon , and put two vias at the proper places using the following two parameter tables.
-3 for Via Depth here means the vias starting from y=0 is extended to ground plane 3 micros in -y direction.
Next, with the vias, we are going to investigate the following four different cases: ON state with small signal simulation, ON state with large signal simulation, OFF state with small signal simulation and OFF state with large signal simulation.
1. ON state with small signal simulation
§ Setting the ON state for Pin Diode and choosing small signal simulation in its parameter table, you can run the simulation and check the simulation results by clicking Both of the performances of S11 and S21 are improved by adding vias. The S11 behaves well up to 50GHz, while S21 is deteriorated when frequency increases.
2. ON state with large signal simulation § To do so, remember to go to Settings and set Yes for Large Signal, and in your Component Properties, select your Diode, or whichever component you are using, and select Large for Signal Simulations:
§ When the Simulation is complete, click on the Results button. You can click on Fundamental, 1st Harmonic, and 2nd Harmonic while holding Ctrl on your keyboard to view all results in the same graph:
3. OFF state with small signal simulation Setting the OFF state for Pin Diode, you can recheck its small signal responses when the vias are on. we can see that vias introduce a greater equivalent capacitor at the air-bridge, which results in a -2dB down for S21 and the deterioration in lower frequency band for S11. In spite of that, the design with vias is much appreciated, because comparing with the enhancement for ON state, the deterioration for OFF state is worthy of being sacrificed.
4. OFF state with large signal simulation You can also recheck its large signal responses when the vias are on. Compared with the ON state, the linear range for 1st and 2st harmonic components are much better. See also |
. You can now start editing your metal in 2D.
, then click and drag to form your first rectangular shape. You can edit your metal shapes’ dimensions and location by Going to Edit Mode
