NI AWR MWOffice Interface Sonnet Advanced Subsectioning Options dialog box

Sonnet Options property page - Subsectioning Options

The Sonnet Advanced Subsectioning Options dialog box is opened when you click on the Advanced button in the Subsectioning Options section of the Sonnet Options property page in the NI AWR MWOffice Interface. This dialog box allows you to control the subsectioning in Sonnet of your translated circuit. Since subsectioning has a direct effect on processing time and accuracy, this allows the experienced user a measure of control over the trade off between them. The controls are explained below.

WARNING:      Be aware that these are advanced options and should not be changed from their default values except by an experienced user who understands the effects of these options.

Maximum Subsection Size: Em uses a variable subsection size. Small subsections are used where needed, such as around corners, and larger subsections are used elsewhere. This reduces the size of the matrix which must be inverted, often providing a dramatic increase in the speed of an analysis. In no case are the subsections smaller than a single cell.

This field allows you to limit the maximum size of the subsection, generated by the analysis engine, in terms of subsections per wavelength. The default of 20, used when this option is not on, is fine for most work and means that the maximum size of a subsection is 18 degrees at the highest frequency of analysis. Increasing this number decreases the maximum subsection size until the limit of 1 subsection = 1 cell is reached.

Estimated Epsilon Effective: Normally, em has an algorithm which estimates the effective dielectric constant used to determine the wavelength used for maximum subsection size. If this option is selected you may override the automatic algorithm and force em to use your dielectric constant to calculate the wavelength which is used in setting the Maximum Subsection size. If this option is not on, Auto appears in the text entry box to indicate that em is using its algorithm to determine the subsectioning frequency.

Polygon Edge Checking: Normally em considers one adjacent metal level in either direction from the present level when computing the subsectioning. This is an important consideration when thin dielectric layers are used. Polygon Edge Checking allows you to override the automatic algorithm and specify how many adjacent levels should be considered when calculating subsections. This entry should be an integer value. Note that entering a value of zero causes em to only look at the present metal level.

Subsectioning Frequency

The analysis engine, em, uses the subsectioning frequency to calculate the wavelength which is used in setting the Maximum subsection size. The subsectioning frequency is determined by the radio buttons described below:

Present and Previous Analyses: This is the default setting for the subsectioning frequency. Select this option if you wish to analyze your project at the highest frequency used in this or any previous run of the project.

Present Analysis Only:  In this case, the highest frequency at which the project is analyzed for this run is used to subsection the circuit.

Previous Analyses Only: Select this option if you wish to analyze your project in a different frequency range than a previous run but wish to use the same subsectioning on your circuit. The maximum frequency from all previous runs on this project will be used as the subsectioning frequency.

Use Fixed Frequency: Select this option to enter the frequency you wish to use for the subsectioning frequency. Enter the desired frequency in the text entry box to the right which is enabled when this option is selected. This frequency will be used as the subsectioning frequency for all analyses of this project.

All Polygon Meshing (AWR to Sonnet)

XMin, XMax, Ymin, YMax: Sonnet allows you to control how cells are combined into subsections for each polygon. This is done using the parameters “X min”, “Y min”, “X max” and “Y max.” These fields are applied as a global setting for all polygons. For a detailed discussion of these parameters and how they affect subsectioning in Sonnet, please refer to the Metalization Properties dialog box.

Use Edge Mesh: When using the Edge Mesh option, all Manhattan polygons (no diagonal edges) are treated as if they were non-Manhattan polygons. In other words, the edge subsections are always one cell wide regardless of X Min or Y Min. This field is applied as a global setting for all polygons. When used in conjunction with large X Min or Y Min values, this option can be very useful in reducing the number of subsections but still maintaining the edge singularity. This is very often a good compromise between accuracy and speed.

Conformal Mesh Subsection Length: You may set a maximum length for a conformal section by selecting this checkbox and entering the desired length in the text entry box below. This is useful in reducing the size of your conformal sections to ensure higher accuracy. The default length of a conformal section is 1/20 of the wavelength of the subsectioning frequency.

All Metal Fill Type: This field allows you to set the fill type for all metal polygons in the translated project. If you do not wish to set a global fill type, select “<off>” from the drop list. If you wish to set a fill type, choose from Staircase, Diagonal or Conformal. For more information on fill types in Sonnet, please refer to the Metalization Properties dialog box.

All Via Fill: This field allows you to set the fill method for all vias in your translated project. If you do not wish to set a global fill method, select “<off>” from the drop list. If you wish to set a fill method, choose from Full, Ring, Vertices or Center. For more information on via fill methods, please see the Via Meshing Fill dialog box.