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Sonnet User's Guide - Sonnet Software

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Chapter 10 Parameterizing your Project<br />

For complete details on all the functions and constants available for equations and<br />

their syntax, please refer to the equation syntax help topics in Help. You may access<br />

these topics by clicking on the Equation Syntax Help button in the Add/Edit<br />

Variable dialog box.<br />

If you enter an equation which uses a variable as the definition of another variable,<br />

then the variable defined by the equation is dependent on the variable used in the<br />

equation. This is discussed later in the chapter, in "Dependent Variables" on page<br />

135.<br />

Frequency Dependency<br />

There is a frequency constant, FREQ, available for use in <strong>Sonnet</strong> equations. This<br />

allows you to model properties whose characteristics are frequency dependent<br />

such as a dielectric. It is important to be aware that if a variable uses the FREQ<br />

constant in its definition that the value of the variable changes during the analysis<br />

even if the variable is NOT selected for the parameter sweep or optimization.<br />

Dependent Variables<br />

One variable is dependent upon another if the value of a variable is defined by an<br />

equation that uses another variable. As the value of the variable in the equation is<br />

changed, so is the dependent variable. If a variable is dependent, you may not directly<br />

edit its nominal value; instead, you change its value by changing the value<br />

of the variable on which it is dependent. You may not delete a dependent variable.<br />

If you wish to delete it, you must first remove the dependency by changing the definition<br />

of the dependent variable.<br />

Variables which do not depend on another variable for their value are independent<br />

variables. Only independent variables may be selected for a parameter sweep. To<br />

vary a dependent variable in a parameter sweep, you must select the variable on<br />

which it depends. For more details on parameter sweeps, see "Parameter Sweep"<br />

on page 148.<br />

Circular Dependencies in Variables<br />

Care should be taken when adding dependent variables to your circuit that they do<br />

not form a circular dependency. A circular dependency is formed when two variables<br />

are dependent on each other. This can happen for two variables or multiple<br />

variables. In the case of multiple variables, the dependency extends from the first<br />

variable through all the variables until the first variable is dependent upon the last.<br />

135

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