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Ansoft Designer / Ansys Designer 在线帮助文档：

Nexxim Simulator >
Nexxim Time-Varying Noise Analysis >
   Running TV Noise Analysis from the Schematic Editor       

Running TV Noise Analysis from the Schematic Editor

From the Schematic Editor, perform the following steps to set up and run a TV Noise analysis using Nexxim.

1. Right-click on the Analysis menu in the Project window to open a menu.

2. Select Add Nexxim Solution Setup from the menu, then slide the cursor to select TV Noise Analysis from the subordinate menu. The TV Noise Analysis dialog box appears.

3. Type an Analysis Name (or accept the default name, for example “TVNoise”).

4. For most simulations, leave the Disable box unselected (the default setting). Selecting this box lets you store multiple solution setups for later use. (Note that if a solution setup is disabled before the analysis is run, any changes made to the design will invalidate the simulation results.)

5. In the Steady State panel, click the Edit Tones/Maxk button. The Edit Tones/Max Harmonic Number dialog opens:

•  Enter the number of tones to be used in the steady-state phase of the analysis. The tones are listed with names F1 ... Fn. These names cannot be changed.

•  Click on a Value field in the row for one of the tones to enter the frequency for the steady-state analysis for that tone.

•  Click on a MaxK field in the row for one of the tones to enter the Max. Harmonic Number for the steady-state analysis for that tone.

•  Click OK to close the Edit Tones/Max Harmonic Number dialog and return to the TV Noise Analysis dialog. The Number of tones field now shows the number of tones you specified in the dialog.

6. Optionally, click on the Edit RelHarmNum button to open the corresponding dialog:

•  The No. of tones, Name, and Value fields reflect the settings from the Edit Tones/Maxk dialog. The number, name, and value of tones cannot be changed in the Edit RelHarmNum dialog.

•  Click in the RelHarmNum field for a frequency to set the relative harmonic number offset for that tone. Refer to the TV Noise Technical Notes topic for information on the use of the RelHarmNum offsets.

Click OK to return to the TV Noise Analysis dialog box.

7. Select the Analysis type from the pulldown. The default is harmonic balance (HB). You can choose oscillator analysis (OSC) instead.

•  When HB is the Analysis type and one-tone analysis has been specified, the Method field is activated. Use this field to select HB or shooting (HB is the default). See Handling Strongly Nonlinear Circuits in the HB topic for details on the Method entry.

•  When HB is the Analysis type, the Auto Refine Solution field is activated. Use this field to select Yes or No (No is the default). See Increasing Accuracy or Speed in the HB topic for details on the Auto Refine Solution entry.

•  When HB is the Analysis type and multi-tone analysis has been specified, the Trim Tolerance field is activated. Use this field to set a tolerance value. See Increasing Accuracy or Speed in the HB topic for details on the Trim Tolerance entry.

8. Optionally, click the Edit button at the lower right of the Steady State panel to add voltages, currents, and harmonic outputs from the underlying analysis (HB or OSC). These additional output quantities are available in the Report dialog after simulation has been performed.

Expand the Nets and devices icons to display lists of the available quantities. To have Nexxim calculate outputs from the steady state analysis step, use the checkboxes to select the outputs.

Expand the Harmonics icon to display a list of the available harmonics. To specify particular harmonics for Nexxim to use when calculating outputs from the steady state analysis step, use the checkboxes to select the harmonics. If you do not select any harmonics, harmonics DC, F1, 2F1, 3F, and 4F1 are automatically selected. In the Report dialog, only selected harmonics are available for plotting.

Click OK to return to the TV Noise Analysis dialog box.

9. TV Noise analysis requires a sweep of input frequencies. Click on the F entry in the Sweep Variables field and click Edit (or Add). The Add/Edit Sweep dialog opens.

•  Use the radio buttons to select one of the following: Single value, Linear step, Linear count, Decade count, or Octave count.

•  Type the sweep values into the Value text box (for Single value), or into the Start, Stop, and Step text boxes (for Linear, Decade, or Octave count), and make sure that the appropriate units are selected for each.

•  Click Add, and then click OK to close the dialog box.

•  The TV Noise Analysis dialog box reappears. The sweep definition appears in the Sweep Variables field. (The Sweep Variables display includes fields labeled Offset of F1 and Sync. These fields are not used by Nexxim TV Noise analysis.)

10. In the Noise panel, use the pulldown in the IProbe field to select a port, current source, or voltage source for the small-signal input to the circuit. If a port is selected, Nexxim computes the noise figure and conversion gain. For current and voltage sources, Nexxim computes the gain, but not the noise figure.

Gain for a port input is calculated in Volts, in the sense of available power. The input units are Volts for a voltage source and Amperes for a current source. If no IProbe input is selected, Nexxim computes the output noise only.

11. Use the pulldown in the OProbe field to select a port, resistor, current source, voltage source, or current probe for the small-signal output from the circuit.

When a port, current source, or resistor is selected, output units are Volts. When a voltage source or current probe is selected, output units are Amperes.

12. Click on the Edit button next to the Noise Output field to open the Noise Output dialog.

•  Expand the Nets and devices icons to display lists of the available quantities. Use the checkboxes to select noise outputs. (The IProbe and OProbe devices are always included as noise data outputs, so they do not appear in the list).

•  Adding a Custom Quantity (Differential Voltage Output) To specify a noise output other than a single node voltage or branch current—for example, a differential voltage such as V(net1,net2)—type the output into the Find field and then click the Add Custom button. (The Add Custom button becomes active when a noise output in the Find field cannot be found in the list of Nets and devices.)

The custom output quantity is passed to the netlist as a NOISE_OUTPUT entry in the TV_NOISE statement. For example, the differential voltage example above would netlist as:

NOISE_OUTPUT=[v(net1,net2)]

No validation is performed on the custom output quantity before it is written out to the netlist.

13. Click OK to close the Noise Output dialog and return to the TV Noise Analysis dialog box.

14. After one or more elements have been added in the Output Noise field, you can use the pulldown in the Input Referred Noise field to select a node voltage or branch current for input-referred noise analysis. The Input Referred Noise selection is active only when at least one item has been selected in the Noise Output field. The Input Referred Noise entry does not have to be the same as any of the Noise Output selections.

15. Optionally, click on the Edit Refsidebands button to open the corresponding dialog:

•  The No. of tones, Name, and Value fields reflect the settings from the Edit Tones/Maxk dialog. The number, names, and values of tones cannot be changed in the Edit Refsidebands dialog.

•  Click in the RefSidebands field for a frequency to set the reference sideband coefficient for that frequency. The REFSIDEBAND coefficients are positive or negative integers plus zero.Refer to the TV Noise Technical Notes topic for information on the use of the Refsidebands quantities.

16. Optionally, click the Save All Sidebands box to have Nexxim store the contributions from all noise sidebands. The default is not to save all contributions to save analysis time and memory usage, since the file is potentially very large.

17. Optionally, use the fields in the Solution Option panel to select or add Hb or OSC analysis options and other Nexxim options to the design.

•  Click the Select button on the Name field to open the Select Solution Options dialog.

If any options sets have been defined, their names appear in the Select Solution Options list. To select a named option set that you have previously defined, click the name of the option set, then click OK to return to the TV Noise Analysis dialog. The named option set appears in the Name field in the Solution Options panel. See Analysis-Specific Options for details on creating option sets outside of the Solution Setup dialog.

To create a new option set, click New. The Solution Options dialog box appears. Use the Name field to name the new option set. Select the HB Options or OSC Options tab. Make the appropriate changes to option values, then click OK to return to the Select Solutions dialog box. On the Select Solutions dialog, click the name of the new option settings, then click OK to return to the TV Noise Analysis dialog. The name of the new option settings appears in the Name field in the Solution Options panel.

•  Click the Edit button on the Additional field to open a text-entry dialog, Edit additional options.

Use the text box to enter any Nexxim options exactly as they are to appear in the netlist. Do not include the keyword .OPTIONS; the .OPTIONS keyword is automatically inserted at the beginning of the line in the netlist statement.

The line can contain multiple options settings. Use spaces to separate the options settings.

To modify or delete an option once it has been added, just edit or delete its entry in the list. To clear all options, delete the entire line.

Click OK to return to the TV Noise Analysis dialog.

The options in the Additional field are automatically added to the netlist when the solution containing them is performed.

18. Click Finish to close the TV Noise Analysis dialog. The solution setup is added to the Project tree under the Analysis icon.

19. Run the simulation:

•  Expand the Analysis icon on the Project tree, click on the desired solution setup, and select Analyze from the menu. If the circuit is set up correctly, the analysis begins immediately and a red progress bar appears.

•  The Message Window signals success or failure.

•  For details on creating and modifying reports, see Generating Reports and Postprocessing.

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