AC Simulation Parameters
ADS provides access to AC simulation parameters enabling you to define aspects of the simulation listed in the following table:
| Tab Name | Description | For details, see... |
|---|---|---|
| Frequency | Sweep type and associated characteristics. | Setting Frequency Sweep |
| Noise | Parameters related to linear noise calculation (including port noise). | Defining Noise Parameters |
| Parameters | Provides options to set the following:
|
Defining Simulation Parameters |
| Output | Selectively save simulation data to a dataset. | For details, see Selectively Saving and Controlling Simulation Data. |
| Display | Control the visibility of simulation parameters on the schematic. | For details, see Displaying Simulation Parameters on the Schematic. |
| Additional parameters that you may find useful. | Additional Parameters |
Setting Frequency Sweep
Setting up the sweep portion of the simulation consists of two basic parts:
- Selecting the sweep type and setting the associated characteristics
- Optionally, specifying a sweep plan
To shorten simulation time in any parameter sweep, select a start point as close as possible to the convergence point and vary the parameter gradually. This yields better estimates for the next simulation, and achieves convergence more rapidly than if the parameter were changed abruptly. The following table describes the parameter details. Names listed in the Parameter Name column are used in netlists and on schematics.
| Setup Dialog Name | Parameter Name | Description | |
|---|---|---|---|
| Frequency | |||
| Sweep Type-The sweep type and parameters. | |||
| Single point | Freq | Enables simulation at a single frequency point. Specify the desired value in the Frequency field. | |
| Linear | Enables sweeping a range of values based on a linear increment. Click Start/Stop to set start and stop values for the sweep, or Center/Span to set the center value and a span of the sweep. | ||
| Log | Enables sweeping a range of values based on a logarithmic increment. Click Start/Stop to set start and stop values for the sweep, or Center/Span to set the center value and a span of the sweep. | ||
| Start/Stop Start, Stop, Step-size, Pts./decade, Num. of pts. |
Start Stop Step Dec Lin |
Select the Start/Stop option to sweep based on start, stop, step-size or pts./decade, and number of points. Linear sweep uses Step-size; Log sweep uses Pts./decade. - Start-the start point of a sweep - Stop-the stop point of a sweep - Step-size-the increments at which the sweep is conducted - Pts./decade-number of points per decade - Num. of pts.-the number of points over which sweep is conducted |
|
| Center/Span Center, Span, Step-size, Pts./decade. Num. of pts. |
Center Span Step Dec Lin |
Select the Center/Span option to sweep based on center and span, step-size or pts./decade, and number of points. Linear sweep uses Step-size; Log sweep uses Pts./decade. - Center-the center point of a sweep - Span-the span of a sweep - Step-size-the increments at which the sweep is conducted - Pts./decade-number of points per decade - Num. of pts.-the number of points over which sweep is conducted |
|
| Note: Changes to any of the Start, Stop, etc. fields causes the remaining fields to be recalculated automatically. | |||
| Use sweep plan | SweepPlan | Enables use of an existing sweep plan component (SweepPlan). Select this option and enter the name of the plan or select it from the drop-down list. | |
Defining Noise Parameters
Defining the noise parameters consists of the following basic parts:
- Enable noise calculation.
- Specifying the nodes to use for noise parameter calculation.
- Specifying the noise contributors and the threshold for noise contribution.
- Optionally, specifying the bandwidth over which the noise simulation is performed.
The following table describes the parameter details. Names listed in the Parameter Name column are used in netlists and on schematics.
| Setup Dialog Name | Parameter Name | Description | |
|---|---|---|---|
| Calculate noise | CalcNoise | This check box enables linear noise simulation. Voltages are reported for nodes, currents are reported for branches. See ns_circle | |
| Nodes for noise parameter calculation-Use this area to select nodes at which you want linear noise data to be reported. Noise voltages and currents are reported in rms units. | |||
| Edit | Enables selection of nodes at which you want noise data reported. | ||
| Select | NoiseNode | Contains the list of named node(s) at which noise parameters are to be reported. First use the Edit field to add named nodes to this window. Add - enables you to add a named node. Cut - enables you to delete a named node. Paste - enables you to take an item that has been cut and place it in a different order. |
|
| Noise contributors-Use this area to sort the noise contributors list and to select a threshold below which noise contributors will not be reported. A list shows how each component contributes to noise at a specific node. The noise contributor data are always in units of V/sqrt(Hz) for noise voltages, and A/sqrt(Hz) for noise currents; they do not scale with noise bandwidth. | |||
| Mode | SortNoise | Provides options for sorting noise contributors by value or name. | |
| Off | Off | Causes no individual noise contributors to be selected. The result is simply a value for total noise at the output. | |
| Sort by value | Sort by value | Sorts individual noise contributors, from largest to smallest, that exceed a user-defined threshold (see below: Dynamic range to display). The subcomponents of the nonlinear devices that generate noise (such as Rb, Rc, Re, Ib, and Ic in a BJT) are listed separately, as well as the total noise from the device. | |
| Sort by name | Sort by name | Causes individual noise contributors to be identified and sorts them alphabetically. The subcomponents of the nonlinear devices that generate noise (such as Rb, Rc, Re, Ib, and Ic in a BJT) are listed separately, as well as the total noise from the device. | |
| Sort by value with no device details | Sort by value with no device details | Sorts individual noise contributors, from largest to smallest, that exceed a user-defined threshold (see below: Dynamic range to display). Unlike Sort by value, only the total noise from nonlinear devices is listed without any subcomponent details. | |
| Sort by name with no device details | Sort by name with no device details | Causes individual noise contributors to be identified and sorts them alphabetically. Unlike Sort by name, only the total noise from nonlinear devices is listed without subcomponent details. | |
| Dynamic range to display | NoiseThresh | A threshold below the total noise, in dB, that determines what noise contributors are reported. All noise contributors less than this threshold will be reported. For example, assuming that the total noise voltage is 10 nV, a setting of 40 dB (a good typical value) ensures that all noise contributors up to 40 dB below 10 nV (that is, up to 0.1 nV) are reported. The default of 0 dB causes all noise contributors to be reported. This parameter is used only with Sort by value and Sort by value with no device details. | |
| Include port noise in node noise voltages | IncludePortNoise | Causes the simulator to model noise at input and output ports. | |
| Bandwidth () | BandwidthForNoise | The bandwidth over which the noise simulation is performed. 1 Hz is the recommended bandwidth for measurements of spectral noise power. The noise contributor data do not scale with noise bandwidth. | |
Defining Simulation Parameters
Defining the simulation parameters consists of the following basic parts:
- Enabling the frequency conversion.
- Enabling the budget simulation.
- Specifying the desired level of detail in the simulation status summary.
- Specifying the amount of device operating-point information to save.
The following table describes the parameter details. Names listed in the Parameter Name column are used in netlists and on schematics.
| Setup Dialog Name | Parameter Name | Description | |
|---|---|---|---|
| Frequency Conversion | |||
| Enable AC frequency conversion | FreqConversion | Causes a frequency-converting AC analysis to be performed. | |
| Budget | |||
| Perform Budget simulation | OutputBudgetIV | Enables Budget simulation, which reports current and voltage data at the pins of devices following a simulation. Current into the nth terminal of a device is identified as ...device_name.tn.i. Voltage at the nth terminal of a device is identified as ...device_name.tn.v. | |
| Levels | Enables you to set the level of detail in the simulation status report. | ||
| Status level | StatusLevel | Prints information about the simulation in the Status/Summary part of the Message Window. - 0 reports little or no information, depending on the simulation engine. - 1 and 2 yield more detail. - Use 3 and 4 sparingly since they increase process size and simulation times considerably. The type of information printed may include the sum of the current errors at each circuit node, whether convergence is achieved, resource usage, and where the dataset is saved. The amount and type of information depends on the status level value and the type of simulation. |
|
| Device operating point level | DevOpPtLevel | Options to save device operating-point information for most active devices and some linear devices in the circuit to the dataset. In ADS, if this simulation performs more than one AC analysis (from multiple AC controllers), the device operating point data for all AC analyses will be saved, not just the last one. Default setting is None | |
| None | None | No information is saved. | |
| Brief | Brief | Saves device currents, power, and some linearized device parameters. | |
| Detailed | Detailed | Saves the operating point values which include the device's currents, power, voltages, and linearized device parameters. | |
Additional Parameters
The following table includes additional parameter(s) that you may find useful.
Additional Parameters
| Setup Dialog Name | Parameter Name | Description |
|---|---|---|
| Other | Use Other to enable access to hidden parameters, and assign values to them. The format is: Other=HiddenParameter1=value1 HiddenParameter2=value2 ... Hidden parameters typically are used when troubleshooting convergence problems. To set this parameter in ADS, select the parameter name on the Display tab, then enter the value directly on the schematic. |
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