# Lesson 8: PrimCalc

PrimCalc is a helpful tool for designing primitives. It allows for two-way design, with synthesis using a simple iterative design approach- some variables are free and the others are fixed.

As an example, for transmission lines such as microstrip, the primitive’s arguments are on one side of the transform- things that describe the physical properties. On the other side of the transform are the impedance (Z0); the effective permittivity (eps_re); and the conductor, dielectric, and total loss (alpha_c, alpha_d, and alpha).

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

Figure 8.1: Calculate electrical properties of the microstrip

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

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 8.2: Synthesize the microstrip from the electrical properties