Autoplot, Probe Circuit, and Snapshot

This chapter describes some additional features of the Data Display including some features designed for the RF Design Environment (RFDE). The Autoplot and Probe Circuit features described in this chapter are provided for Cadence users who have installed RFDE and want to take advantage of the automated Data Display plotting capability.
The features described in this chapter are:

• Autoplot in RFDE

• Probe Circuit in RFDE

• Snapshot

Autoplot in RFDE

Autoplot in RF Design Environment enables you to control whether or not to automatically launch a Data Display window with your simulation results after a simulation is run. The Autoplot feature is enabled by default.
A Data Display window can be accessed in RFDE:

• When you click the Plot Outputs button.

• When you select the Results > Plot Outputs menu item.
• After a simulation is run if Autoplot enabled .

To enable/disable Autoplot:

1. Choose Results > Data Display Options .
   The Data Display Options form appears.
2. Select the Open Data Display After Simulation option if you want to automatically launch a Data Display window after a simulation has completed. Deselect the option to disable this feature.
3. Select the Translate Results to PSF option if you want your output dataset translated to parameter storage format (PSF), Cadence's native data format. This will enable you to view your output in the Cadence Waveform Viewer. For information on this option, see the Using Circuit Simulators manual, "Simulation Basics" chapter, "Dataset-to-PSF Conversion in RFDE" section.
4. Select the Enable Automatic Plotting of Output option if you want to automatically display the outputs defined on the Outputs section of the Simulation window. When a measurement expression is added and this option is enabled, a new plot will be created for the expression. Deselect the option to disable this feature.
5. The _
   Dataset Used for Automatic Plotting_ option defaults to Use most recent dataset . Most analyses produce only a single dataset. However, distributed simulation and wireless test bench can produce multiple datasets. The Prompt for dataset selection enables you to choose from the available datasets during Plot Outputs.
6. Click OK to save your settings.

   Note A separate plot is generated in the Data Display for each analysis type (i.e., AC, DC, HB, SP, Tran, and Env).

Probe Circuit in RFDE

The Probe Circuit feature enables you to interactively select voltages and currents from the simulation or schematic window for plotting in RF Design Environment. You can plot common outputs quickly by choosing Results > Probe Circuit from the main menu and then selecting a net or terminal in the schematic window. The Probe Circuit interface also provides access to a pre-defined set of measurement expressions for the various analysis types. For information on the pre-defined set of measurement expressions, refer to Expression Builder in the Measurement Expressions documentation.
Before you can plot your results in a Data Display window, you need to run or have already run, a simulation.

To use Probe Circuit after running a simulation:

1. Choose Results > Probe Circuit . Note that the menu is divided into two sections. The top section includes quick access menu items that only require you to select a voltage or current on the schematic to display the results. The bottom section of the Probe Circuit menu displays a list of analysis types (see the following table). After selecting an analysis type, the Probe Circuit form appears enabling you to further define your output.

   Analysis Type	Measurement Description
   DC	DC Simulation
   AC	AC Simulation
   SP	S-parameter Simulation
   Tran	Transient (Time-Domain) Simulation
   HB	Harmonic Balance Simulation
   LSSP	Large-Signal S-parameter Simulation
   Env	Circuit Envelope Simulation

   Note Some menu items in the Probe Circuit menu may be inactive if the corresponding analysis data is not available.

2. In the Probe Circuit form, select the desired output option from the Plot Options section. The Probe Circuit Plot Options are described in the following table.
   

   Plot Option	Description
   Create a new plot	Probe circuit default. Enables you to add outputs from schematic to a new plot.
   Add a trace to the selected plot	Enables you to add multiple traces in a single plot.
   Print numerical data	Enables you to display your data in a tabular format.

3. The Analysis Type pull-down menu defaults to the analysis selected from the menu item. You can select any analysis type in the menu; however, if the analysis data for that particular type is not available, a Data Not Available message is displayed in the Measurement pull-down menu.
4. The Measurement pull-down menu contains a set of pre-defined measurement expressions to choose from. Use the Measurement pull-down menu to select a specific measurement.

   Note Depending on how your environment is configured, you may need to expand the Probe Circuit form to display all of the options available for each measurement.

5. Click the Select button next to the desired voltage or current and view the prompt in the schematic window. The prompt displayed will tell you what to select in the schematic window. The prompts are described in the following table.

   Prompt	Description
   Select a net	This prompt appears when selecting a voltage.
   Select a current probe or voltage source	This prompt appears when selecting a current. Because the simulator does not compute terminal currents, you will need to select a current probe or voltage source instance.

6. Select the signal necessary for the function. The net name will be added to the field for the item you selected.
7. For certain outputs, you can select a specific Window Type . Windowing is used to reduce discrete Fourier transform (DFT) leakage. For more information on Window Types, refer to the ts() function in the Measurement Expressions documentation.
   Depending on your selection, additional options are listed which enable you to further define your outputs. Several example options are shown in the following table.

   Options	Description
   Number of Points	This field accepts either an integer or a string variable.
   Stop Time	This field accepts either a Real number or a string variable.
   Harmonic Index	This field accepts a Vector number in the form {0, 2}.
   S-parameter	For Probe Circuit, this field is a selection field.

   For detailed information on specific options, refer to the Expression Builder ** in the Measurement Expressions documentation.

8. After selecting all of your voltages and/or currents and entering any other appropriate information, click OK in the Probe Circuit form. The Data Display is launched with your results.
9. You can add additional traces to your plot by selecting Add a trace to the selected plot or display your data in tabular form by selecting Print numerical data as described in the table of Probe Circuit Plot Options.

Snapshot

If you are running a long simulation and you want to look at data for a particular point in your design, or you just want to check the progress of your simulation, you can take a Snapshot of the simulation results to quickly view the data.

Snapshot in RFDE

To enable Snapshot mode, you first need to select your outputs. If you have not selected any outputs on the schematic, the result will produce a blank Data Display window. Also, if the simulation is not running, clicking the Plot Outputs button will launch a blank Data Display or a plain Data Display with the plots that you have configured for it.
To setup and enable a Snapshot:

1. Choose Outputs > To Be Plotted > Select on Schematic .
2. Use your cursor to select an output on the schematic. You can add additional outputs by simply continuing to click points in your design.
   An entry for each selected output appears in the Outputs section of the Circuit Design Environment window. Note that the Plot column displays yes for each of the selected outputs.
3. Once you have all of your outputs defined, choose Simulation > Netlist and Run or click the Netlist and Run button to launch your simulation.
4. At any point during the simulation, choose Results > Plot Outputs or click the Plot Outputs button to display a Snapshot of your results.
   The Data Display window is launched with your simulation data for that particular point in time.

While Snapshot makes sense for longer simulations, Autoplot in RFDE is recommended for shorter simulations.

Note Most Cadence users are familiar with the Cadence Snapshot mode which launches the Cadence Waveform Viewer. In contrast, the RFDE Snapshot mode launches the Agilent Data Display.

Snapshot in ADS

To launch a snapshot during a simulation from an Advanced Design System schematic window:
Choose Simulation > Snapshot . When a snapshot is triggered in ADS, the snapshot display is updated soon after the next available swept point in done. If a previous request is being processed, the subsequent request is ignored and a status window is displayed that says,
Snapshot is being processed, please wait...
The dataset is then updated and the data display window is launched.

Note If the data display window associated with the particular design or simulation has been previously configured, the window should display the appropriate graph or output. However, if you have not configured the data display window for your specific simulation, an empty data display window that includes the dataset attached may appear.

Some additional details for ADS snapshot:

• A snapshot request that is sent after a simulation is completed will be ignored.
• Snapshot is not available for Momentum simulations.
• Snapshot is supported for remote simulations.
• Results of source currents (e.g. include, I-Probe) and voltages of named nodes can be displayed in snapshot; however, measurement data are not always valid. If the measurement variable is defined on a point base (i.e. does not cross sweep points), and it is defined in the output plan inside the analysis, it can be displayed in snapshot. Otherwise, the data will be invalid.