Viewing Results in EMDS

This chapter shows how to display EMDS for ADS results.

Viewing Results Using the Data Display

You have two tools available for displaying the results of an EMDS for ADS simulation: the Data Display, and EMDS for ADS Visualization. The visualization tool is described in following chapters. This chapter describes how to use the Data Display.
You can display S-parameter data from an EMDS for ADS simulation. Additional data is calculated during a simulation and saved in the dataset, and can also be viewed or used in calculations:

• Propagation constant (gamma) for each port in the circuit
• Characteristic impedance of each port
  For detailed information on how to use the Data Display, refer to the "Data Display" manual.

Opening a Data Display Window

You view simulation results using the Data Display. You can open a Data Display window using different methods:

• Open a Data Display window automatically when a simulation is complete. For steps on how to do this, refer to Viewing Results Automatically.

• Open a new Data Display by choosing Window > New Data Display from the Layout Window menu bar.
• Open a saved Data Display by choosing Window > Open Data Display and selecting a Data Display in the current project. Data Display files end in the extension . dds .

Viewing the EMDS for ADS Data

Simulated EMDS for ADS data is saved in one or more datasets:

• Data collected at the frequency points computed by the simulator are stored in < design_name >.ds . It is the standard dataset created from any simulation.
• If the Adaptive sweep type is used for simulation, densely resampled data, computed by AFS at each sampled frequency point, are stored in the dataset < design_name >_a.ds .
  The datasets for the current project are displayed in the dataset listbox.
  
  You can view EMDS for ADS data using any plot type:
  
  To view EMDS for ADS data:

1. Select the plot type by clicking the appropriate plot icon, dragging the mouse into the window, then clicking to place the plot.
2. The variables in the default dataset are displayed. Select a different dataset from the list, if desired.
3. Select the variables containing the data that you want to add to the plot, then click Add .

   Note Most of the simulation data is in complex format. If you are adding data to a rectangular plot, you must choose to display the data in one of several scalar formats.

4. You can add data from different datasets to the same plot. Repeat steps two and three to add more data to the plot.
5. Click OK to view the data.
   

   Note Multiple graphs within the same view will overlay one another. To view multiple graphs simultaneously, assign each graph to a separate view.

Viewing S-parameters

Specific information about the data available in the S-parameter datasets is given in the following sections.

Variables in the Standard and AFS Dataset

Variable	Description
freq	The independent variable frequency, which was specified during the simulation setup. The number of data points is based on the sweep type and frequency plans specified during simulation.
PORTZ n	The impedance of Port n as defined in the Impedance fields of the Port Editor dialog box. If an impedance is not specified, 50 ohms is assumed.
S	S matrix, normalized to PORTZ n .
S( i , j )	S-parameters for each pairing of ports in the circuit, normalized to PORTZ n .

Standard and AFS Datasets

If the Adaptive sweep type is used for a simulation, two datasets are created for storing data. The first one contains data computed by the simulator at the frequency points determined during the simulation. (This dataset is the standard one produced by any simulation.) The second contains data computed by AFS, resampled with a very dense frequency distribution. This "adaptive" dataset is denoted by _a appended to the dataset name. The adaptive dataset contains the same variables as the standard dataset, but data is calculated for a significantly greater number of frequency points.

Typically, when viewing data in the _a dataset, you should see very smooth results, which reflect the behavior of the circuit. Viewing the standard dataset on the same plot will show the frequency points for which the simulator was invoked, superimposed on the smooth curve. Those frequency points will be scattered over the whole range, with relatively more points grouped in areas where the S-parameters show more variation. Viewing both datasets can help you determine the quality of the AFS process on your simulation. For more information on AFS, refer to About Adaptive Frequency Sampling.

Viewing Results Using EMDS for ADS Visualization

In EMDS for ADS Visualization, you can display S-parameters in tabular or plotted formats. This chapter describes how to view and work with S-parameters. It also gives general information about S-parameters.

S-parameter Overview

When viewing and working with S-parameters, you should be aware how impedance is specified and what naming convention is used. These are described in the following sections.

Normalization Impedance

The S-parameters that you can display are S-parameters with respect to a normalization impedance as defined in the Impedance fields of the Port Editor dialog box. If an impedance is not specified, 50 is assumed.

Naming Convention

The S-parameter naming convention, which is based on the name of the project, indicates which set of S-parameters you are viewing or working with. There are only two datasets available for a project. One is named design_name which contains the discrete frequencies that were actually simulated. The second is design_name(afs) is available only when an adaptive frequency sweep is specified in the simulation setup. An adaptive frequency sweep dataset contains a high resolution sampling based on the pole-zero model fitted on the simulated frequencies.

Viewing S-parameters in Tabular Format

You can view S-parameters in tabular format. The table displays S-parameter values for each port in these formats:

• Magnitude
• Real and imaginary components
• Magnitude and phase

The table is for viewing data only, you cannot plot data from this table.
S-parameters are displayed as shown here.

To view S-parameters:

1. Choose Plot > Matrix.
2. Select the data you want to view from the S Parameters list.
3. Select the frequency of interest from the Frequencies list. Some S matrices have data at only one frequency.
4. Select the data format:
   • *Magnitude * Displays the magnitude of the S-parameters
   • *Real/Imag * Displays the S-parameters as complex numbers
   • *Mag/Phase * Displays the magnitude and phase of the S-parameters
5. Use the scroll bars to view large matrices.
6. Click OK to dismiss the dialog box.

Plotting S-parameter Magnitude

The S-parameter magnitude plot displays magnitude in dB with respect to frequency.

To display an S-parameter magnitude plot:

1. Choose Plot > Mag Plot.
2. Select an S matrix from the Matrix List.
3. Select the S-parameters. The combinations are based on ports.
4. Select the view where you want to display the plot.
5. Click Apply.
6. You can add other S-parameters to the plot, or click Done to dismiss the dialog box.

Plotting S-parameter Phase

The S-parameter phase plot displays phase in degrees with respect to frequency. Note that when viewing S-parameter phase, in some cases the phase delay is plotted. For example, a layout of an electrical length with a phase of 60 degrees, S ₂₁ represents a phase delay, and appears as -60 degrees. For phases greater than 180 degrees, it may appear that the phase predicted from Gamma compared to S ₂₁ is incorrect, but this is not so if delay is taken into account.

To display an S-parameter phase plot:

1. Choose Plot > Phase Plot.
2. Select an S matrix from the Matrix List.
3. Select the S-parameters. The combinations are based on ports.
4. Select the view where you want to display the plot.
5. Click Apply.
6. You can add other S-parameters to the plot, or click Done to dismiss the dialog box.

Plotting S-parameters on a Smith Chart

The Smith chart displays real and imaginary components of S-parameters.

To display a Smith chart:

1. Choose Plot > Smith Plot.
2. Select an S matrix from the Matrix List.
3. Select the S-parameters.
4. Select the view where you want to display the plot.
5. Click Apply.
6. You can add other S-parameters to the Smith chart, or click Done to dismiss the dialog box.

Exporting S-parameters

S-parameters can be exported to a file, in either Touchstone or CITIfile format. You can export S-parameters to use with other tools.

To export S-parameters:

1. Choose File > Export S Matrix .
2. Select the set of S-parameters to be exported from the Matrix list.
3. Select the file format, CITIfile or Touchstone.
4. Specify the file name either by typing the full file path into the File Name field or click Browse.
5. Click OK to complete the command.