Creating Wireless Test Bench Designs for RFDE

Introduction

Using Ptolemy in ADS, a system designer can create a DSP system design that is available to an RFIC designer as a wireless test bench (WTB) model. The wireless test bench is a mechanism by which a system designer can make system measurements available to an RFIC designer. The RFIC designer can then validate and verify the RFIC design or device under test (DUT).
This appendix describes how to create and verify, then export a WTB design to RFDE.

Creating a Wireless Test Bench Design

Creating wireless test bench designs using Ptolemy components in ADS is similar to setting up other Analog/RF designs for cosimulation. The design must be created in a DSP schematic using only DSP components.
The WTB design can be split between two parts.

• The first part of the WTB design is the group of components that generate a signal appropriate for simulating the RFIC or DUT. Ports (appropriately named) added at the output of this part of the design will act as WTB model output and DUT input when used in RFDE.
• The second part of the WTB design is the group of components that process the DUT output and perform various system measurements using Ptolemy Sink components. Ports (appropriately named) added at the input of this part of the design act as WTB model input and DUT output.
  The input ports must have an EnvOutSelector or EnvOutShort (from the Circuit Cosimulation library) to select the correct frequency to be extracted from the Circuit Envelope analysis of the DUT for system measurement. Any port that is not connected to an EnvOutSelector or EnvOutShort is considered to be an output port.
  A DF controller (from the Controller library) must be added to the design that uses the correct setup of scheduler type, deadlock manager, and other parameters.
  Create the WTB design parameters that the RFIC designer can use to modify the WTB design's configuration, using the File > Design Parameters in the ADS schematic window.

Wireless Test Bench Design Examples

For examples on how to create a WTB design for export to RFDE, look at the designs listed with the example projects in Wireless Test Bench Design Examples. Each design has instances of the pre-configured WTB model components. Push into the components to view the design.

These projects are contained in the TDSCDMA, WCDMA3G, and WLAN Design Libraries and can be installed by using the custom installation option.

Note RangeCheck components used in the pre-configured WTB designs are created specifically for those WTB designs. Do not use the RangeCheck components when you create your own WTB designs.

Setting the Units for WTB Design Parameters

The system designer can use the list of units provided in the Design Parameter dialog box to correctly specify the unit used for a parameter. If the parameter value is a unit that is not part of the list, such as percent , and the system designer wants to communicate the units to the RFIC designer, then the unit can be placed within parentheses at the end of the parameter's description text.

Categorizing WTB Design Parameters

WTB designs support a feature that enables a person using the WTB design to categorize the parameters. It is helpful for the System designer to group the parameters in a way that makes it easier for the RFIC designer.
To categorize the list of parameters, define a string type of parameter at the beginning of the group of parameters that belong in a category. The parameter must have a description field specified that contains a very short description of the category. The parameter's default value must be set to Category to identify this parameter as a categorization parameter. And, the parameter's attributes must be set such that it will not be netlisted and not displayed.
The group of parameters will appear in different tabs in the Wireless Test Bench Setup dialog in RFDE. The first group of parameters are considered Required Parameters and will appear in a separate widget along with the ports in the top half of the Wireless Test Bench Setup dialog box. These parameters are considered as parameters that must have value (they cannot be blank). All subsequent groups of parameters will be considered as optional parameters for modification.

Information Parameters

The system designer can insert various information parameters that describe a particular aspect of the WTB design, such as instructions related to timing setup. To create such a parameter, define a string type of parameter and set its attribute such that it will not be netlisted and will not be displayed on the schematic. Leave the parameter's default value blank.

Verifying a WTB Design in ADS

To verify a WTB design in ADS:

1. Create a DUT in ADS. Add an Envelope controller inside this DUT.
2. Open a new DSP schematic window.
3. Add an instance of the WTB design and the instance of the DUT; connect them.
4. Add a WTB controller.
5. Simulate this design and generate the dataset to verify the results.

   Important Do not use more than one unconnected DUT design or Envelope controller during WTB design verification in ADS.

Exporting a WTB Design to RFDE

After creating a WTB design as described in Creating a Wireless Test Bench Design, export the design so it can be used in RFDE. To export the WTB design, save it and select Tools > Export WTB Design to RFDE in the schematic window containing the design. An Export Status/Error/Warning dialog box appears showing the exporting progress. A temporary design window will open where the WTB design will be instantiated before the export starts.

A successful export process generates the files < WTBname > _TB.il and < WTBname > _TB.net. These files are saved with the exported design under the project directory ..._prj/adsptolemy/wtb .

WTB Design User Interface Attributes

Each WTB design has a category to which it belongs. The category name is the project name from which it was exported without the _prj extension.
The WTB design name is same as the corresponding design name.
The Wireless Test Bench Setup dialog in RFDE contains a pull-down list of categories. Each category selection updates another pull-down list containing WTB models exported from a single project.
Following the WTB model selection pull-down list is the Required Parameters widget that contains the ports that can be connected to the DUT, along with the first group of parameters created by the system designer. If no categories are created, all of the parameters are included as part of this widget. The items in this widget cannot be left blank, or unspecified, and must contain some value. To aid WTB model and DUT port connection, a button is provided, per port, that takes the RFIC designer to the schematic window to select a pin on the DUT.
Following the Required Parameters widget is a widget containing tabs for all subsequent parameter groups. The tab name is the description specified for the categorization parameter. These parameters are optional parameters for modification.

Creating a Results Display for WTB Designs

A WTB design can have complex data that the RFIC designer will not know how to interpret. To help simplify data analysis, the System designer must use the following steps:

1. System designer must use a simple DUT in ADS to create a dataset.
2. Open a new DDS window. Add one or more new pages and name them appropriately.
3. Leave page 1 untouched and blank; this page is used for other Analog/RF automatic plots.
4. Add correct equations/plots/configurations on the new pages.
5. Save this DDS file as a template by choosing File > Save as Template on the DDS window. Select the User category to save the template.
6. The template file is saved under $HOME/hpeesof/circuit/templates .
7. Copy the template file to _prj/adsptolemy/templates .
8. Place an OutputOption controller in the WTB design's schematic window. (The OutputOption component can be placed at any level of hierarchy in the WTB design.)
9. Add the data display template name, created above, to the list of names. More than one data display template is allowed for a given WTB design.
10. Re-export the WTB design.
    Now, when this WTB design is used in an RFDE simulation, the templates named in the OutputOption controller will be inserted in the DDS window that appears at the end of the simulation.

Circuit Envelope Parameters

Some parameters must be defined as WTB design parameters to ensure compliance with Circuit Envelope requirements within the WTB design's simulation setup.

• CE_TimeStep The WTB design must have a CE_TimeStep parameter that enables the RFIC designer to set the Circuit Envelope time step. If this parameter is not added to a WTB design, the time step will always be set to 0.01msec.
• FSource The WTB design can optionally have an FSource parameter to enable the RFIC designer to set the source carrier frequency. This parameter will automatically be added to the Fundamental Tones parameters of Circuit Envelope after the WTB design is set up in RFDE. To ensure correct behavior this frequency must not be deleted from the Fundamental Tones .
• FMeasurement The WTB design can optionally have an FMeasurement parameter to enable the RFIC designer to set the measurement carrier frequency. This parameter will automatically be added to the Fundamental Tones parameters of Circuit Envelope after the WTB design is set up in RFDE. To ensure correct behavior this frequency must not be deleted from the Fundamental Tones .