PrimCalc is a tool for designing transmission line elements. It has a two-way design capabilities: for the calculation of electrical properties based on the physical properties, and the synthesis of physical properties using a simple iterative design approach- some physical variables are checked as "free" and some electrical properties are checked as "fixed".

As an example, for transmission lines such as microstrip, the physical properties are defined on the left column- things like the width, the height, and the dielectric properties. On the right column are the electrical properties such as the impedance (Z0); the effective permittivity (eps_re); and the conductor, dielectric, and total loss (alpha_c, alpha_d, and alpha). Additionally, an image of the geometry and a description of the model are included.

The first time PrimCalc is run on a primitive (such as microstrip/mcurve.xml) it will create a template for input and output of PrimCalc (mcurve.pci). After that, PrimCalc will remember the last values entered.

For a standard installation, the Mason models used in PrimCalc should be located at: "C:\Documents and Settings\All Users\Application Data\CircuitMason\mason_models"

Designing from Physical Properties to Electrical Properties

Enter in the desired values on the left, with no boxes checked, and "Calc".

Figure 1: Calculate electrical properties of the microstrip (Click to enlarge)

Designing from Electrical Properties to Physical Properties

Designing from electrical properties requires some initial guesses on the left column; this can be from a previous run. Leaving boxes blank is a bad idea.

Check those boxes on the right column that you want to define: perhaps the line impedance and the line length. Check those boxes on the left column that you would like to be free: perhaps the line width and line length. You can synthesize based on one or more parameters on each side. Try not to over-specify.

Figure 2: Synthesize the microstrip from the electrical properties (Click to enlarge)


Copyright 2010, Gregory Kiesel