HFSS15: Applications for Deembedding

Deembedding helps to calculate the S-parameters near or on the plane of a discontinuity or when a long transmission line is attached to the port plane instead of explicitly modeling it in HFSS. For lossless ports, when you deembed them into or out of the model, there is change only in the phase of the S-parameters but not in the magnitude. For lossy ports, aside of the change in the phase of the S-parameters, there is only a slight change in the magnitude. Deembedding saves time and significantly reduces the simulation efforts.

Extract Input Impedance: Use Deembedding

This section describes how to extract the input impedance in the microstrip fed patch antenna model shown in the figure below. The port (highlighted in red ink) is placed at an appropriate distance away from the discontinuity. We cannot place the port near the intersection of the trace and the patch antenna i.e. at the discontinuity. However, if you want to measure the input impedance at the discontinuity, you can deembed the port as shown by the blue arrow in the figure.

For lossless ports, deembedding will not change the magnitude of the S-parameters. It will only change the phase.