Getting Started with RFIC Dynamic Link

This tutorial steps you through the process of simulating a circuit using components from the Agilent version of the analogLib library. Other examples are also included to help you become familiar with the product.

Both the drop-down menus and icons are described to help familiarize you with the Advanced Design System environment.

Setting up the Examples Directory

To set up the examples directory, first ensure that:

• The HPEESOF_DIR environment variable is set to your ADS installation directory
• $HPEESOF_DIR/bin is in your PATH
• Your environment is set up to run the Cadence icms or msfb tool

From any directory of your choice, enter:

cp -r $HPEESOF_DIR/idf/examples ./

cd examples

Note This must be done before attempting the Getting Started Tutorial. The cds.lib file under the examples directory defines libraries provided by Dynamic Link. The .cdsinit file under this directory loads the Dynamic Link .cdsinit file which then loads the context files required to run Dynamic Link.

Starting the Cadence Design Framework

Ensure that you are in the examples directory then launch Cadence Design Framework II by typing the appropriate command (typically icms or msfb ). The Cadence Command Interpreter Window (CIW) appears.

Cadence CIW Window

Note Non-standard or customized start-up scripts for Cadence Design Framework II may not be supported. If you have difficulties, contact your system administrator.

Opening a Cadence Composer Schematic

To open a schematic cellview in Cadence Composer:

1. Choose File > Open from the Cadence CIW. The Cadence Open File form appears.
   
2. Select examples from the Library Name drop-down list.
3. Click PowerAmp in the Cell Names list. This sets the Cell Name field to PowerAmp.
4. Select schematic from the View Name drop-down list if not already selected.
5. Select the edit Mode if not already selected.

   Note To open a file in edit mode you must have write permission.

6. Click OK . The Cadence examples, PowerAmp schematic cellview appears.
   

Cadence Virtuoso Schematic Composer Window

Linking with Advanced Design System

To link the Cadence design environment to Advanced Design System:

1. Choose Tools > ADS Dynamic Link from the menu bar in the Cadence Schematic window. In a few moments, the Advanced Design System Main window appears in the upper-left hand corner of your display.
   

   Advanced Design System Main Window

   Note Depending on your system, it may take a few moments for the ADS windows to appear. View the Cadence CIW window for the link status.

2. From the ADS Main window, choose File > Open Project and select the examples_prj project. The ADS Schematic window displays a DynamicLink menu item and is automatically titled untitled1 (see the following figure).
   
   

   Advanced Design System Schematic Window

At this point, ADS and the Cadence Design Framework II are working together.

Opening a Test Schematic Design

To open a test schematic design:

1. Choose File > Open Design in the ADS Schematic window to display the Open Design dialog box. Use this dialog box to select the design you wish to simulate.
   
2. The examples_prj selection in the Project drop-down list is set by default in the Open Design dialog box.
3. Select PowerAmp_test.dsn from the Designs list. The PowerAmp_test.dsn schematic contains simulation components that can be selectively activated or deactivated.
4. Click OK to include the PowerAmp_test.dsn schematic in the ADS Schematic window.

Adding a Symbol of the Cadence Cellview

To add a symbol of the Cadence cellview in the Advanced Design System Schematic window:

1. Choose DynamicLink > Instance > Add Instance of Cellview in the ADS Schematic window.
   
   

   Adding a Cellview

   A Select Design dialog box appears, enabling you to select the Cadence Cellview to simulate.
   

2. In the Cell Name field of this dialog, verify the entry or type the name of the Cellview you want to simulate (in this case PowerAmp ). Alternatively, you can use the Browse button and library manager to select the name.
3. Click OK . A symbol of your Cadence Cellview is automatically generated.
4. An instance of the symbol is attached to the cursor for you to place. In the Advanced Design System Schematic window, click the left mouse button to place the symbol as desired.
5. You may continue placing more instances of the same cellview, or, in this case, choose the Cancel Command And Return To Select Mode icon to proceed with the next step. Similarly, you may place instances of other Cadence designs.

Adding Design Variables

To add the design variables from the Cadence Cellview to the ADS schematic window choose DynamicLink > Design Variables > Get Design Variables .
This places a corresponding VAR component on the ADS schematic containing the design variables from Cadence (i.e. Rcc, Rout, Remitin and Remitout).

Adding Model Files

To add a model file

1. Choose DynamicLink > Add Netlist File Include
2. Place the NetlistInclude component in an open area on the schematic.
3. Double click the include component icon. The Netlist File Include dialog box appears.
   
4. In the Netlist File Include dialog box, click IncludeFiles in the Select Parameter list box. The Model Library File field appears in the dialog box.
5. Click Browse just below the Model Library File field to locate the first model library file. The Select File dialog box appears.
   
6. In the Select File dialog box, use the Directories field to locate the models directory.
   <your_current_working_dir> /examples/models
   This sets the path for the location of the model library files.
7. In the Select File dialog box, use the Files field to locate and click the npnpwa1.ads model file, then click OK . An information message appears stating that a new path has been added to the include path list.
   
   Click OK in the Information Message dialog box. You are returned to the Netlist File Include dialog box.
8. In the Netlist File Include dialog box, notice that the Model Library File field now contains the npnpwa1.ads model file. Click Apply to add the npnpwa1.ads model file.
9. Click Browse again to locate the second model library file. The Select File dialog box appears.
10. In the Select File dialog box, use the Files field to locate and click the npnpwa2.ads model file, then click OK . You are returned to the Netlist File Include dialog box.
11. In the Netlist File Include dialog box, notice that the Model Library File field now contains the npnpwa2.ads model file. Click Add to add the npnpwa2.ads model file.
12. The Select Parameter field should now contain the information below.
    IncludeFiles[1]=npnpwa1.ads
    IncludeFiles[2]=npnpwa2.ads.
13. Click OK in the Netlist File Include dialog box.
    For more information on the Netlist File Include Component, refer to Adding Model Files.

Performing a DC Simulation

To run a DC simulation on an ADS schematic and then annotate the results to the Cadence Composer Window:

1. Choose Edit > Component > Deactivate/Activate then click the DC component in the ADS Schematic window to toggle and activate the component. Alternatively, you can choose the Deactivate/Activate Components icon to activate the DC component.
   
   
   

   Activating Components in an ADS Schematic Window

2. Choose Simulate > Simulate or choose the Simulate icon to run a simulation. A simulation dialog box appears in your display.
   
3. After the simulation is complete, a Data Display window titled PowerAmp_test automatically appears. Close this window using the File > Close Window menu option.
4. Click the PowerAmp schematic symbol in the ADS Schematic window.
5. Choose DynamicLink > Annotate > Annotate DC Solution to Selected Cellview . This displays the DC node voltages on the Cadence schematic.
   
   

   Cadence Schematic with Annotated Display

Annotating DC Operating Points to a Selected Cellview

Any simulation that includes a DC analysis produces DC operating point information for most active and some passive devices in the circuit. This data includes currents, power, voltages, and linearized device parameters of the selected device.

To run a DC Operating Point Simulation on an ADS schematic and then annotate the results to the Cadence Composer Window:

1. Double-click the DC Simulation component in the ADS schematic window. The DC Operating Point Simulation dialog box appears.
   
2. Click the Parameters tab in the DC Operating Point Simulation dialog box.
3. Click Detailed in the Device operating point level section of the DC Operating Point

   Note For a subset of the detailed DC Operating Point Simulation information that covers most common parameters, click Brief in the Device operating point level section of the DC Operating Point Simulation dialog box.

4. Choose Simulate > Simulate or choose the Simulate icon to run a simulation. A simulation dialog box appears in your display.
5. After the simulation is complete, a Data Display window titled PowerAmp_test automatically appears. Close this window using the File > Close Window menu option.
6. Click the PowerAmp schematic symbol in the ADS Schematic window.
7. Choose DynamicLink > Annotate > Annotate Operating Points to Selected Cellview . This displays the DC operating point values for each component on the Cadence schematic.
   
   

   Annotated Cellview with DC Operating Points

   Saving Node Voltages and Pin Currents with RFIC Dynamic Link  

With the RFIC Dynamic Link Probing feature, you can select nodes or pins of interest in a Cadence subcircuit and display their voltages or currents in an ADS Data Display window.

The following is an example session using the Dynamic Link Probing feature with the PowerAmp example.

1. Double click the DC Simulation controller component in the ADS schematic window to open the DC Operating Point Simulation dialog box.
   
2. Click the Output tab in the DC Operating Point Simulation dialog box.
3. Click Add/Remove in the Output section of the DC Operating Point Simulation dialog box to open the Edit OutputPlandialog box.
   
4. Click the + sign to the left of the X1 component in the Available Outputsfield to start Dynamic Link Node Probing setup. This raises the Cadence schematic window containing the PowerAmp cellview. The prompt in the Cadence schematic window is changed to: ADS Probing Setup: Click a wire or a pin>.
5. Click the right pin of the R0 resistor on the upper-left region of the schematic window. "X1.R0.MINUS.pinCurrent.i" appears in the Current Selection field on the right side of the ADS Edit OutputPlan dialog box.
6. Click the collector pin at the top of the Q1 BJT. "X1.Q1.C.pinCurrent.i" appears in the Current Selection field on the right side of the ADS Edit OutputPlan dialog box.
7. Click the vertical net connected from above Q1 to the collector pin of the Q1 BJT. "X1.net44" appears in the Current Selection field on the right side of the ADS Edit OutputPlan dialog box.
8. Click the vertical net connected from below Q1 to the emitter pin of the Q1 BJT. "X1.net12" appears in the Current Selection field on the right side of the ADS Edit OutputPlan dialog box.
   
9. Click OK in the ADS Edit OutputPlan dialog box to close the dialog box. The DC Operating Point Simulation dialog box should now appear similar to the following figure.
   
10. Click OK in the DC Operating Point Simulation dialog box to instruct ADS to save currents for X1.R0.MINUS and X1.Q1.C in addition to voltage values for X1.net12 and X2.net44 after DC simulation.
11. Click the Simulate icon or select Simulate > Simulate menu item in the ADS schematic window to run a DC Simulation. The ADS Data Display window appears automatically once the ADS DC Simulation is complete.
12. Click the List icon on the left of the Data Display window, then click a desired location in the ADS Data Display window to bring up the Plot Traces & Attributes dialog box.
    
13. In the Plot Traces & Attributes dialog box, press the Ctrl key and click the following four items on the left, then click >>Add>> in the middle to add these four items to the Traces field on the right.

    C.pinCurrent.i
    MINUS.pinCurrent.i
    net12
    net44

14. Click OK to close the Plot Traces & Attributes dialog box. The currents of R0.MINUS and Q1.C pins and voltages of net12 and net44 are immediately listed in the ADS Data Display window.

Additional Notes:

• When the Add/Remove button in the DC Operating Point Simulation dialog box is clicked to bring up the Edit OutputPlan dialog box, as described in step 6 above, all of the named nodes and subcircuit components at current circuit level appear in the Available Outputs field on the left. You can select a named node from the Available Outputs field and then click Add>> to add it to the Current Selection field on the right. You can also remove a named node from the Current Selection field by clicking <<Remove after selecting it.
• Clicking the + sign to the left of a subcircuit component in the Available Outputs field displays all the named nodes and subcircuit components within that subcircuit. In step 7 above, nothing was displayed initially because there was no named node or subcircuit in the PowerAmp cellview.
• After a Cadence schematic window is raised as a result of clicking the + sign mentioned above, any named or unnamed node in the Cadence subcircuit hierarchy can be selected by clicking the left mouse button at any point on the wire. To select a node in Cadence subcircuit, choose Design > Hierarchy > Descend Edit menu item in the Cadence schematic window, click OK in the form popped up, and then click a wire of interest. Valid selections are limited to the current window and the current circuit hierarchy.
• During the Node Probing operation, the left mouse button in the Cadence Virtuoso schematic window is mapped to a Dynamic Link SKILL procedure. Do not bind any function to the left mouse button during this period. Any bindkey function previously mapped to the left mouse button will not work until the tune mode ends.

Performing an S-parameter Simulation

To perform an S-parameter Simulation on an ADS schematic:

1. Deactivate the DC component using the Deactivate/Activate toggle.
2. Activate the S-parameter component using the Deactivate/Activate toggle.The ADS schematic is now ready to simulate an S-parameter.
   
   

   Activating Components in an ADS Schematic Window

3. Choose Simulate > Simulate or choose the Simulate icon to run the S-parameter simulation.
   After the simulation is complete, a Data Display window titled PowerAmp_test automatically appears.
   

   Note The amplifier used in this tutorial is not a traditional microwave amplifier for use by itself. It is meant to be used as part of an RFIC, where it takes a small voltage signal and converts it into a current for driving a larger-signal amplifier, off chip. It has not been designed to have S 11 and S 22 less than 1. More simulations are run on the amplifier in the ADS example file, IQ_Mod_from_MDS_prj.zap, which you can download from the Agilent EEsof EDA external Web site. The example described in this document is only illustrating the RFIC Dynamic Link for Cadence.

Displaying Your Results

To view the results of your simulation in a plotted Data Display:

1. Select PowerAmp_test from the Default Dataset __ drop-down list if not already selected.
2. From the Data Display window, choose Insert > Plot , move the frame to an appropriate location within the window and click. This anchors a frame for your plot. Similarly, you can choose the Rectangular Plot icon to drag and drop the plot frame.
3. The Plot Traces & Attributes dialog box appears. Select S(2,1) and then click Add . Select dB from the dialog box then click OK .
   
4. Click OK again to view the Data Display .

   Note The following figure shows the forward gain, S(2,1), at 1.9 GHz to be approximately 12.57 dB. By varying the value of Remitout in this case, you can modify the circuit to achieve the desired results. After you have completed the tutorial, take some time to experiment with different values of Remitout .

Data Display with S-parameter Simulation Results

Performing a Parameter Optimization

To optimize the parameters of Var1 in the ADS schematic:

1. Choose the Deactivate/Activate Components icon then place the cross hair over the Nominal Optimization component to toggle and activate the component. Repeat this step for the Goal component. The ADS schematic is now ready to optimize the S-parameter.
   
   

   Activating Components in an ADS Schematic Window

2. Choose Edit > Component > Edit Component Parameters and then click the VAR component. The Variables and equations dialog box appears.
3. In the Variables and equations dialog box, select the parameter Remitout in the Select Parameter field.
4. Click the Tune/Opt/Stat/DOE Setup button. The Setup dialog box appears.
5. Click the Optimization tab and set the Optimization status to Enabled .
6. Set the Minimum Value to 120 and the Maximum Value to 200 .
   
7. Click OK twice, once in the Setup dialog box and once in the Variables and equations dialog box. Note that the Remitout parameter on the ADS schematic now displays:
   Remitout= 163 opt{120 to 200}
8. Choose Simulate > Simulate or choose the Simulate icon. This netlists each Cadence subcircuit in the Affirma Analog Circuit Design Environment , as well as the top-level ADS schematic, and starts the Advanced Design System simulator.
   

   Note A simulation status window appears, reporting the status of the simulation; depending on your system, this may take some time. Check this status window to see if any errors occurred during netlisting or simulation.

   After the simulation is complete, a Data Display window titled PowerAmp_test automatically appears. For information on configuring the Data Display, refer to Displaying Your Results.
   

   Note The following figure shows the optimized forward gain, S(2,1), at 1.9 GHz to be approximately 13.08dB as set by the Goal component in the ADS Schematic window.

   
   

   Data Display with Optimized Simulation Results

9. Choose Simulate > Update Optimized Values to update the optimized values. This changes the value of Remitout in the VAR component to the optimized value.
10. Choose DynamicLink > Design Variables > Update Design Variables to Cellviews to update the optimized value to the Cadence cellview. A Confirmation Message dialog box appears.
    
11. Click the Close button.
12. From the Cadence menu bar, choose DynamicLink > Design Variables . A Design Variables form appears.

    Note If the DynamicLink pull-down menu does not appear in the Cadence Virtuoso Schematic window, choose Tools > ADS Dynamic Link in the Cadence schematic window.

13. Click Copy From in the Cellview Variables section. This enables you to update the design variables to the Artist session.
    

Verifying Your Results

You may now verify the results of your optimization by using the optimized value of Remitout in an S-parameter simulation . Set the value of Remitout = 120 (approximate optimum value) and repeat the steps in Performing an S-parameter Simulation __ with the new value of Remitout.

Note The following figure again shows the optimized forward gain, S(2,1), at 1.9 GHz to be approximately 13.08 dB as set by the Goal component in the ADS Schematic window. By using the optimized value of Remitout , you have verified the optimum desired results of the circuit.

Data Display with Optimized Simulation Results

Ending the Session

Use the following steps to exit the Dynamic Link environment and close both ADS and Cadence.

1. Choose the Advanced Design System Schematic menu option DynamicLink > Close Cadence Connection . This closes ADS and terminates the link between Cadence and the Advanced Design System.
2. Exit from the Cadence CIW.
3. Congratulations... you have now successfully completed the Tutorial.