L, M, K, R-Transformer

There are four transformer measurements:

• L-Transformer: The self inductance of each coil of the transformer
• M-Transformer: The mutual inductance between two coils of the transformer
• K-Transformer: The coupling coefficient between two coils of the transformer
• R-Transformer: The resistance of the transformer

These measurements are based on simple Pi network of two coupled inductors in a  two port circuit as shown below. However, the equations are valid for an N-port circuit

Note that it is very important that the ports for the coupled inductors are set up correctly in Sonnet. You either need to use differential ports or ensure that the inductors are connected to ground as shown in the schematic. If you choose not to use differential ports, you may use a circuit simulator or a Sonnet netlist project to short the inductor ports.

While the schematic above depicts a two port circuit, this model can be used to represent any number of ports.

L-Transformer is computed as follows:

where Znn is the z-parameter for selected port n from the Ports section of the Properties pane below.

M-Transformer is computed as follows:

where Zmn is the z-parameter for selected ports m and n from the Ports section of the Properties pane below.

K-Transformer is computed from z-parameters as follows:

where m and n are the To and From ports, respectively, specified in the Properties pane of the Manage Curves dialog box.

Please see the Measurement Properties topic for an explanation of each field in this dialog box.