Tuning in Advanced Design System

Advanced Design System's tuning capability enables you to change one or more design parameter values and quickly see its effect on the output without re-simulating the entire design. Multiple traces generated from various tuning trials can be overlaid in the Data Display window. This can help you find the best results and the most sensitive components or parameters more easily.

Note
The tuning feature described in this documentation is not supported in RF Design Environment for Cadence. This feature is available for Advanced Design System and RFIC Dynamic Link schematic only.

This topic includes:

When you analyze a network (Simulate > Simulate), a considerable amount of information is compiled by the simulator prior to the actual network simulation. The simulator must set up your network topology, load all the values of the component parameters, and organize your measurement requests.

With the ADS tuning features, you can avoid repeating the pre-processing. Tuning performs the pre-processing once and then assumes that you are now just trying to change some of the parameter values. A new simulation will take place, but using the same network topology and list of measurements. Only the small changes regarding the new parameter values are needed. You can tune a large number of components, including those that are processed by a measurement equation component, such as VSWR.

Before you get started tuning, you can optionally set up your tuning preferences by choosing the Options > Preferences menu item and then selecting the Tuning tab. For more information, Setting Tuning Options.

Tuning Benefits

The benefits of the ADS tuning feature include:

Basic Tuning Procedure

Before starting any tuning session, you must first meet the prerequisites listed below.

Tuning Prerequisites

  1. Build your design.
  2. Set up your simulation.
  3. Simulate your design and verify that your simulation operates as expected.
  4. Set up, display, and analyze your results in the Data Display window.

Basic Tuning Procedure

The basic tuning procedure consists of the following steps:

  1. Start Tuning – Start the tuning application by choosing the Simulate > Tuning menu item or click the Tune Parameters icon. For more information, refer to Tuning Parameters.
  2. Select Parameters – Click the parameter(s) you want to tune. For more information, refer to Setting Up Parameters Inside of Tuning.
  3. Tune Parameters – Move the sliders or click the up or down arrow to tune a parameter. For more information, refer to Tuning Parameters.
  4. Use Memory Traces – Use memory traces to store intermediate results. For more information, refer to Managing Parameter Values and Traces.
  5. Update the Schematic – Update your schematic with the new values and save your design. For more information, refer to Updating Your Design.

Using the Tune Syntax

The tune syntax is added to tunable parameters in the schematic window when you select a parameter for tuning. The tuning syntax uses the form:

y = x tune{ min to max [by step | logScale ] }

where

y is the parameter name
x is the parameter value, in specified units
min is the minimum parameter tune value, in specified units
max is the maximum parameter tune value, in specified units
by step is a linear parameter step value, in specified units. This is an optional argument; however, if it is not selected, you must select logScale.
logScale is the logarithmic scale. This is an optional scale setting; however, if it is not selected, you must select a linear scale; that is, by step.

For example, a resistor with a nominal value of 50 ohms that you want to tune from 25 to 75 ohms in increments of 5 ohms would take the form:

R = 50 Ohms tune{25 Ohms to 75 Ohms by 5 Ohms}

The three modes used in the tune Setup dialog box include:

Note that parameter values can be edited directly on the schematic using the appropriate tuning syntax. Use the examples above as a guide to editing your tuning parameters.

When you launch tuning, parameters that use the tune syntax will automatically be included in your tuning session.

Note that the tune syntax is part of the parameter value itself, so when you save your ADS design, the tuning information will also be saved.

If a component you have selected does not include the Tune/Opt/Stat/DOE Setup button, you may need to manually include the tuning syntax for the parameter.

Abbreviating the Tune Syntax

Parameter values using the tune syntax can be set to appear abbreviated on the schematic. To change the behavior of how the tune syntax appears on the schematic,

  1. From the schematic window, choose Options > Preferences . The Preferences for Schematic dialog box appears.
  2. Select the Component Text/Wire Label tab. The Format section on the Component Text/Wire Label tab includes Tune format attributes which can be set to Full , Short, or None using the appropriate radio buttons.
    • Full is the syntax described in Using the Tune Syntax. For example, 50 Ohm tune{25 Ohm to 75 Ohm by 5 Ohm}
    • Short is an abbreviated syntax: {t} for tune and {-t} for notune. For example, 50 Ohm {t}
    • None will only display the nominal values in the annotation. For example, 50 Ohm
Note
On-screen editing of the Short or None formatted component text will expand to the Full format. Also when using Edit > Component > Edit Component Parameters to edit the tune syntax of a component, the associated dialog box will always display component text in Full format. After editing using either of these methods, the component text on the schematic will continue to be in the format specified by the schematic preferences.

For more information, refer to Setting Component Text/Wire Label Options (in Advance).

Tuning Hierarchical Networks

If your schematic design is hierarchical, that is, if it contains subnetworks, you can tune the components within those subnetworks without having to exit tuning.

While in the Tune Parameters mode, select Push Into Hierarchy from the View menu in the Schematic window or choose the Push Into Hierarchy icon. Click the subnetwork of interest. The Schematic window now displays the subnetwork design. At this point, you can proceed to tune parameters inside the subnetwork.

Note
Changes are made at the definition level, not the instance level. Therefore, if you update a subnetwork using tune mode, all instances of that subnetwork will be changed, not just the one you are pushed into.

Tunable and Non-Tunable Parameters

Most Advanced Design System parameters can be tuned; however, not all can. The following rules govern whether or not a parameter can be tuned. In order for a parameter to be tunable, all of the following statements must be true:

Next are some examples of these rules.

Note
To use the ADS Ptolemy Simulation (Signal Processing) Interactive Controls and Displays library components (such as TkPlot) with tune mode, you must dismiss the Interactive Controls and Displays component between each tune with its pop-up dialog box.

Choosing Tuning Parameters

There are different ways of selecting tune parameters depending on whether you are outside or inside of the tuning application.

For more information, refer to Setting Up Parameters Inside of Tuning.

Note
It is recommended that you only tune about four to five parameters during any one tuning session. While you can generally tune as many parameters as you like, selecting more than four or five may make it difficult to keep track of which changes are impacting your design.

Setting Up Parameters Outside of Tuning

When choosing a parameter that you want to tune, you have the option of defining the tuning setup. To set up a tunable parameter:

  1. Double-click the component that contains the parameter(s) you want to tune. The Edit Component dialog box appears.
  2. In the Select Parameter field, click the parameter that you want to set up for tuning and then click the Tune/Opt/Stat/DOE Setup button. The Setup dialog box appears.
    Note
    Some components or component parameters are not tunable. For example, a component that has no nominal value assigned will not be tunable; the Tuning tab will be greyed out in the Setup dialog box. For more information, refer to Tunable and Non-Tunable Parameters.
  3. Click the Tuning tab and then select Enabled from the Tuning Status pull-down menu item. The Tuning Status drop-down list provides three choices,
    • Enabled – When this option is selected, the parameter will be activated for tuning.
    • Disabled – The parameter is deactivated for tuning; however, the setup information is retained.
    • Clear – The parameter is deactivated for tuning and there is no setup information.
  4. Setup the Minimum Value, Maximum Value, Step Value, and Scale (Linear or Logarithmic) settings for the enabled parameter. Note that you can change these values later during your tuning session as needed.
  5. Click OK to close the Setup dialog.

Tuning Parameters

After fulfilling the prerequisites defined in the Basic Tuning Procedure, you are ready to launch a tuning session.

  1. Click the Tune Parameters icon (tuning fork), or choose the Simulate > Tuning menu item. The Tune Parameters dialog box appears. The following table provides a brief description of the features.
    Tune Parameters Dialog Box
    Section Option Description
    Simulate After Pressing Tune Perform an analysis only after the Tune button is clicked. This option is designed for tuning after multiple changes, but can also be used for single changes. †
    After Each Change Perform an analysis after each change. †
    While Slider Moves Performs continual analyses while moving the slider. This option is similar to the "After Each Change" option, except that it is continuous. †
    Tune Tune the design. This button is active only when the "After Pressing Tune" option is selected.
    Parameters Include Opt Params Include parameters that are enabled for optimization. If the optimization-enabled parameter does not already have a tuning setup, the optimization setup will be used for tuning.
    Enable/Disable Launches the Enable/Disable Parameters dialog box. This dialog box is used to enable disabled parameters and disable enabled parameters.
      Snap Slider to Step For parameters tuned in a Linear scale, the slider moves in increments of the step when "Snap Slider to Step" is selected. Otherwise, the slider moves continuously. For parameters tuned in a Logarithmic scale, the slider moves continuously, regardless of the "Snap Slider to Step" option's setting. †
    Traces and Values Store Stores the tuned parameter values in temporary storage and creates a memory trace for each trace in the Data Display. Note that when you close tuning, all of the stored traces and values are deleted.
    Recall Restores the parameter values for a specified, previously-stored state. Note that if you have changed which parameters have been tuned since the state was originally stored, you may need to choose between the original values at the time the state was stored and the current values. At this point you will be asked to choose between Original or Current. ††
    Trace Visibility Lists all of the stored states and enables you to specify whether a memory trace is visible. ††
    Reset Values Resets the tuned parameters to their nominal values.
    Tuned Parameters Update Schematic Updates the schematic with the tuned parameter values.
    Close Closes the Tune Parameters dialog box. Note that all stored states and memory traces will be deleted.
    Help Launches the online help.
    Value Change the value of the parameter.
    Max Enter the maximum value for the parameter's tuning range.
    Min Enter the minimum value for the parameter's tuning range.
    Step Enter a value that represents the step size. When the up/down arrow buttons are clicked, the value will increment/decrement by the step size. This value is also used to create the slider increments when the "Snap Slider to Step" option is selected.
    Scale Select a Linear or Logarithmic slider scaling. †
    † The default setting for this option is defined by the user preference settings. To set user preferences, choose Options > Preferences and select the Tuning tab.
    †† If there are no stored traces and values, this button will be deactivated.
  2. Move your cursor over the schematic. Notice that the crosshairs appear in the window. This lets you select the tune parameters.
  3. Click a parameter that you want to tune. The Tune Parameters dialog box is updated with a new slider for the parameter selected and the schematic is updated with the tune syntax.

The method above describes how to select individual parameters from the schematic. Alternatively, you can click any component in the schematic. A separate Instance Tunable Parameters dialog box is launched enabling you to choose from among all of the component's tunable parameters as shown in the dialog box below.

Setting Up Parameters Inside of Tuning

Note that you can modify each parameter's, Max, Min, Step, and Scale settings after initiating a tuning session. If the parameter is specified as an integer, the tuning application will constrain the parameter value to integer values. If you attempt to set the Max less than the parameter value, the value automatically changes to the Max. Similarly, if you attempt to set the Min greater than the parameter value, the value automatically changes to the Min. Step is ignored if you select a logarithmic scale for a parameter. Note that the step field is grayed out when the Scale is set to Log. The Min and the Value must be positive when using a logarithmic scale.

Enabling and Disabling Parameters

Click the Enable/Disable button inside the Tune Parameters dialog box to launch the Enable/Disable Parameters dialog box. This dialog displays all of the parameters in the hierarchy that are enabled or disabled for tuning.

Deselecting a tunable parameter simply disables the parameter by changing the tuning syntax from tune to notune . For example, a component parameter that is set up for tuning but has been disabled will appear similar to the following,

S = 18 mil notune{15 mil to 25 mil by 5 mil}

Note that the disabled tuning syntax uses notune as opposed to tune . The tuning set up is maintained.

Managing Parameter Values and Traces

Advanced Design System provides additional capability that enables you to store the tuned parameter values to memory, recall these tuned parameter values, and modify the visibility of the stored values' memory traces. Having your results stored also enables you to return to a stored state at any time during the tuning session.

Storing Values and Traces

  1. Click the Store button to create your trace data and store parameter settings to memory. The Store Traces and Values dialog box appears.

    A default Name and Comment will appear in the dialog box. The Comment defaults to the tuned parameter names and values. When using Legends in Data Display, both the Name and Comment appear in the legend for identification purposes. For more information on legends, refer to the Data Display.

    Example Plot Legend

    Names are always required while Comments are optional. Comments should be kept concise in order to fit well within Data Display legends. This is important for general readability as well as documentation. Notice in the previous figure how a relatively short comment can quickly expand the width of the legend.

  2. Enter a unique name and comment for your tuning state. For example, you might accept the default memory1 and enter good stability as a comment.
    You can alternatively select the name of a previously stored state from the drop-down list in the Name field. This enables you to overwrite the previous state with the current values. Note that this will delete the previous stored state's memory trace and create a new one. A confirmation dialog will appear asking if you want to overwrite state.
  3. Click OK to save your memory trace and return to your tuning session.
    Notice that the memory trace is now displayed with a dotted trace type (see the following figure) in your Data Display window along with your current data trace. As you continue to tune your parameters, you can compare your existing trace with the trace you have stored in memory.

    Example Memory Trace (dotted trace)
  4. If after some additional tuning, you want to store another state, click the Store button again to store your new trace data and parameter settings to memory. The Store Traces and Values dialog box appears again.
  5. Enter a new name and comment for your new tuning state and click OK .
    The new memory trace is also displayed with a dotted trace type in your Data Display window along with your original memory trace and your current data trace. As you continue to tune your parameters, you can compare your existing trace with the two traces you have stored in memory.

Setting Trace Visibility

The Trace Visibility button in the Tune Parameters dialog box enables you to display or hide one or more stored memory traces in the Data Display window. To display or hide a stored memory trace,

  1. Click the Trace Visibility button. The Trace Visibility dialog box appears.

    When you deselect a memory trace in the Trace Visibility dialog box, the visibility of the memory trace is turned off in the Data Display window after you click Apply or OK. The memory trace is still available. It is just not displayed.
  2. Individually select the memory traces that you want to be visible in the Data Display window. If you want all traces visible, click Select All.
  3. Deselect the memory traces that you want to hide in the Data Display window. If you do not want any of the traces visible, click Deselect All.
  4. Click Apply to preview your selections in the Data Display.
  5. If you are satisfied with your settings, click OK .

Recalling Values

You can recall parameter values that you have stored by clicking the Recall button in the Tune Parameters dialog box. To recall tuned parameter values that you have previously stored,

  1. Click the Recall button in the Tune Parameters dialog box. The Recall Traces and Values dialog box appears containing a list of each of your stored states.
  2. Click the stored state that you want to recall and then click OK . The parameters are recalled from memory and the Data Display window is updated.
    Note that if you have changed which parameters have been tuned since the state was originally stored, you may need to choose between the original values at the time the state was stored and the current values for the parameters that were not saved. At this point you will be asked to choose between Original or Current.
Note
Memory traces are frozen. They are not reevaluated as tuning continues. If you change the equation that defines a memory trace, the memory trace will not be reevaluated using the modified expression. Also, if you delete a data trace in the Data Display, all of its associated memory traces will also be deleted. You can change memory trace display properties such as line type, color, thickness, etc. For more information, refer to Editing Traces.

Updating Your Design

To update the design with the values of the tuned parameters:

  1. Click the Update Schematic button to transfer your tuned parameter values to the schematic.
  2. Click the Close button to close the Tune Parameters dialog box.
  3. Save your schematic design. If you want to use your old and new improved designs for comparison later on, save the design with a new name.

Tuning Examples

This section includes examples that are intended to help with your understanding of various tuning topics. The examples provided in this section include the following topics:

Analog/RF Systems Tuning Example

This section shows a tuning example for Analog/RF Systems simulation. If you want to follow the similar steps for a Signal Processing example, skip to Signal Processing Tuning Example.

The following figure shows part of the two-section microstrip filter with a 12 GHz bandpass example. Parameters of the three components shown here will be tuned in this example.


Two Section Microstrip Filter Example

The project containing this design can be copied from your examples directory.

$HPEESOF_DIR/examples/Tutorial/Learn_Tune_prj

Using the example above, you will vary the effect of the filter by tuning the microstrip coupled-line filter components and observing plots of S 11 and S 21 while tuning. The MCFIL component instance CLin2's spacing parameter will be tuned after first tuning the width parameters for the CLin3 and CLin4 instances. Before you begin tuning, you will first need to copy the example project and simulate the initial design.

To practice tuning the example circuit shown in the previous figure, perform the following steps:

  1. Copy the example project to a working directory where you have write permission.
  2. Open tune_example.dsn and simulate the design.
  3. Choose Simulate > Simulate or click the Simulate icon from the toolbar.
  4. After the simulation has finished, a Data Display is automatically launched with a rectangular plot in the Data Display window. The plot shows the results for S 21 and S 11 in dB.
  5. Place a marker on the S 21 trace at 12 GHz to use as a reference while tuning by selecting the Marker > New menu item.

    Initial Simulation Results

    You can also add a legend to your plot using the Insert > Plot Legend menu item if desired. For more information on markers and legends, refer to the Data Display.

  6. Choose Simulate > Tuning or choose the Tune Parameters icon (tuning fork) from the toolbar.
  7. Wait for the initial analysis to complete. The Tune Parameters dialog box appears with CLin4.W and CLin3.W already enabled for tuning.
  8. While observing the Data Display window, move the sliders up and down. Notice how the center frequency of the bandpass shifts up or down while tuning.
  9. Now move your cursor over the schematic and notice that the crosshairs are active. Locate and click the component MCFIL CLin2 instance on the schematic (see the following figure).

    MCFIL CLin2 Instance Showing S (spacing) Parameter

    After clicking the component, the Instance Tunable Parameters dialog box appears with a list of parameters as shown below.

  10. For the MCFIL component CLin2 instance (shown in the figure with MCFIL above), select the S (spacing) parameter in the Instance Tunable Parameters dialog box and click OK .
  11. Notice that the Tune Parameters dialog box is updated with a new CLin2.S tuning slider as shown below.
  12. Select the tune analysis mode from the Simulate drop-down list in the Tune Parameters dialog box. This specifies when you want tuning to occur in the program. For this example, start with the While Slider Moves option.
    Try using each tuning analysis method (A fter Pressing Tune , After Each Change , While Slider Moves ) to see which one works best for you. For more information on the Tune Parameters dialog box, refer to Tuning Parameters.
    The results of the tuning session are displayed in the same Data Display window that the initial simulation was displayed in.
  13. You can change the tunable parameter by using any of the following methods:

    Move the slider up or down

    Click the up or down arrow

    Manually enter a new value into the dialog box

    Change the parameter values in the Tune Parameters dialog box for the tune_example.CLin2.S (spacing) parameter using a Min value of 15 mil (slightly below in the initial value of 18 mil), a Max value of 25 mil, and a Step value of 5 mil as shown below.

    Notice that the tune syntax in the schematic window automatically updates with the new values you entered in the Tune Parameters dialog. For more information on the syntax, refer to Using the Tune Syntax.

  14. Move the slider up and down and observe the results in the Data Display each time you make a change.
  15. You can click the Update Schematic button if you want the value you currently have entered in the Tune Parameters dialog box to be written to your schematic.
  16. Click Close to exit the Tune Parameters dialog box.

For more practice tuning, try experimenting with the other tuning features using the other designs provided in the $HPEESOF_DIR./examples/Tutorial/Learn_Tune_prj ADS example project.

Signal Processing Tuning Example

This section shows a tuning example for Signal Processing simulation. The steps are generally the same as in the Analog/RF Systems Tuning Example, but this example uses a Signal Processing design.

The design in the following figure consists of a sine wave source, a gain component, and a numeric sink.


Sine Wave Source with Gain Component and Numeric Sink

To build the example circuit shown in the previous figure,

  1. Place the following components into a DSP schematic design window:
    • A Sine Gen:Sine wave output component from the Common Components palette
    • A Gain:gain value component from the Common Components palette
    • A Numeric Sink:Numeric Data Sink component from the Common Components palette
    • A Data Flow Controller (DF) from the Controllers palette.
  2. Connect the sine wave generator, the gain value component, and the Numeric Sink using the Insert Wire icon.
  3. Change the component settings so they match the settings in the previous figure.
  4. After you have entered all of your changes, save your design.
    Note If your complete design has not been saved, the tuning application will not consider the components in the design hierarchy and an error message will be reported when you attempt to set up a component parameter for tuning.
  5. Simulate the design.
  6. Set up the Data Display window to display N1 (from the numeric sink). Note that you may need to change the Y Axis to accommodate the changes during your tuning session. Before any tuning occurs, the initial simulation results should appear as shown in the following figure.

    Initial Results

After the initial simulation, tune the circuit by following the procedure below:

  1. Choose Simulate > Tuning or choose the Tune Parameters icon from the toolbar.
    The Tune Parameters dialog box appears.
  2. Move your cursor over the schematic and notice that the crosshairs are active. Locate and click the Gain parameter in the Gain component on the schematic. Note that the G1.Gain parameter now appears with a slider in the Tune Parameters dialog box as shown in the following figure.

    Tune Parameters with G1.Gain Parameter Setup

    The Gain component parameter in the schematic window also displays the tune syntax as shown in the next figure. For more information on the syntax, refer to Using the Tune Syntax.

    Gain Parameter with Tune Syntax
  3. In the Tune Parameters dialog box, select the tune analysis mode from the Simulate drop-down list. This tells the tuning application when you want tuning to occur. For this example, choose After each change .
    After you have completed this example, try going back and using the different tuning analysis modes ( After Pressing Tune , After Each Change , While Slider Moves ) to see which one works best for you. For more information on the different tuning modes, refer to Tuning Parameters.
  4. You can change the tunable parameter by using any of the following methods:

    Move the slider

    Click the up or down arrows

    Enter a new value directly in the field

    Change the parameter values in the Tune Parameters dialog box for the G1.Gain parameter using a Min value of 0.8 , a Max value of 1.2 , and a Step value of 0.1 .
    As you vary the slider, the results of your tuning session are displayed in the same Data Display window that the initial simulation was displayed in.
    The next two figures below show the simulation results for a minimum gain of 0.8 and a maximum gain of 1.2 respectively.

    Results with G1.Gain Slider Set to 0.8


    Results with G1.Gain Slider Set to 1.2
  5. Once you are satisfied with your results, click the Update Schematic button in the Tune Parameters dialog box to update the parameter value in the schematic. If you do not want to change the values in your schematic, continue tuning or click the Close button to end the tuning session.
 

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