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Design Notes
Warning: When run with a new values, the calculation time for this project will be extremely long (much greater than 1 hour).
CoPlanar Waveguide X-Model (EM-Based Model) Autofill Project
The purpose of this project is to create a template by which the databases of all of CPW X-Models can be automatically filled for the nominal value of the substrate. The high accuracy of an X-model is obtained by filling a database with automatically generated EM simulations. While these simulations can take an extremely long time, they only have to be performed once for a given substrate. See "X-Models" in the Microwave Office Element's Guide in the Supplimental Model Information chapter for details on the operation of X-Models. For common substrates, these tables are generated by AWR, Inc., thus saving the user the time required to fill the interpolation tables. AWR provides information in the documentation listed about what models are included with the installatio
n.
Due to the long simulation times, X-Models have a hidden parameter (Autofill parameter), which allows the user to start an autonomous mode, which fills the entire interpolation database without user interaction. This project takes all of the CPW X-models and places them in a schematic with a CPW substrate. The Autofill parameter for each of these elements has been set to 1 (1 Autofill mode, 0 is Normal Mode.) Further, the auto fill parameter has been made visible for clarity. Since Microwave Office is results driven, a measurement of this circuit has been incorporated in order to instigate the filling of the databases.
X-Model Parameter Types
For each X-model there are three types of parameters. User's should be aware of these to understand if they need to fill new X-model databases or not. For each X-model, the complete model set includes the parameters for the model and the parameters for the substrate definition used by the model.
Fixed Parameters: These are parameters used to find the specific X-Model table created for that must match exactly between what is set on the model and the X-model file (*.emx). If there isn't an exact match, you will get an error if the models Autofill parameter is 0 or the simulator will generate the X-model file if the Autofill parameter is 1.
Statistical Parameters: These are parameters that are matched with a fixed parameter. The statistical parameter can have any name and the matched fixed parameter will have the same name but end with Nom. The parameter ending with Nom is used to find the specific f X-Model table that must match exactly between what is set on the model and the X-model file (*.emx). The other parameter (non Nom) value defines the value of the parameter used in the model simulation. The most common example of are Er and ErNom. The statistical parameter value can vary 10% from the Nom value before a warning is issued and 20% before an error occurs. There are two benefits to what was listed above.
1. You may not need to fill new X-model tables to use X-models. For example, lets say your substrate Er is 10. You know that a table for Er=9.8 was included with the software. You set Er = 10 and ErNom = 9.8 and you can simulate with the accurate X-Models.
2. You can do statistical analysis with any of these parameters. For example, if you have an ErNom filled for 10 but you know your substrate Er will vary by 5%, you can still use X-models and do statistical analysis allowing Er to vary.
Independent Parameters: These are the parameters that scale the X-models. These parameters are not used to find tables, rather scale the X-model appropriately.
CPW Parameter Types
For the line models (CPWLINX), the fixed parameters are: Tand,H1,H2,T,Rho, ErNom and Acc. The statistical parameters are: Er. The rest are independent parameters.
For the discontinuity Models (SSBND90X,SSOPENX, SSSTEPX, SSTEEX and SSCROSSX ), the fixed parameters are: H1,H2, and ErNom. The statistical parameters are: Er. The rest are independent parameters.
Use of this Project
If a user wishes to completely fill X-model databases for all of the CPW elements for particular substrate parameters not previously filled, then this project can be used as a template to expedite user interaction.
Step 1) Open the "Autofill CoPlanar Waveguide" Schematic
Step 2) Edit the parameters on the substrate to reflect the desired substrate to be filled.
Step 3) [Optional] Display a 3-D view of the "EM_Work_Space" EM Structure if the user wishes to see the different structures as they are simulated.
Step 4) Simulate the project.
Importantly, the automatic filling of the databases proceeds autonomously and does not require user interaction. Due to the simulation time required to fill these databases, it is recommended that the user not attempt to use the computer while this operation is being performed. In fact the project will automatically complete without the user being present. The total simulation time will depends upon the computer on which the simulation is being performed. The user should assume that the simulation will run for at least 4 hours and plan accordingly. We do NOT recommend that you try to fill two X-model databases at one time.
X-Model Files
The X-Model tables are stored as binary (non-ASCII) files in several locations. The EM_Models folder (directory) located under the root directory of the AWR Design Environment contains the X-Model tables shipped with the software. The appdatauser/em_models folder (directory) contains the X-Model tables generated by users. The best way to find this directory is to select Help > Show Files/Directories and then double click on the appdatauser folder. When the software looks for X-model tables, this is NOT done by the filename, so these files can be named anything you like as long as they have a .EMX extension. The current X-Models shipped with AWR are named in this format:
<type>_<dielectric>_<model>.EMX
<type> will be CPW,Microstrip, Stripline, Suspended_Microstrip, or Suspended_Stripline
<dielectric> will list the fixed and statistical parameters used to create the X-model.
<model> is the name of the model that uses that table.
When X-models are filled with this project, the following files will be created. The XXX will be a three digit number. The name after each file is the model that uses this file.
CP90BXXX.EMX CPWBENDX
CPABGXXX.EMX CPWABRGX
CPTAXXX.EMX CPWTEEX
CPTXXXX.EMX CPWLINX
CPTXXXX.EMX CPWLINX (must create two versions of this model)
After the fill process is complete, we recommend you rename these files for several reasons:
1. If you give them a meaningful name, you will know the Parameter value used to create the file.
2. If you know which models you have filled, it will be easy to copy these files when you upgrade software versions.
To help with the renaming process, there is a Visual Basic script included in this project. See "AWRDE API Scripting Guide" in the help for how work with scripts. When you run this script, it will look for the files listed above, move them to a folder called appdatauser/em_models/CPW, and rename the files. The files are moved to this folder so you know which files are the newly created files and make sure the file names look correct. When you are happy with the names, you will need to copy them back to the appdatauser/ em_models folder for the software to find them. You can change part of the script code to customize how the files are named, there is a comment in the code where to do this.