Adding Ports

Before the circuit can be analyzed, you must add ports. So the next task is to extend the feedlines to the box walls, add ports and then set reference planes so that the effects of the added feedlines are removed by the de-embedding process. This may all be accomplished by the use of a single command when the feedline is the same width as the polygon to which it will be connected.

De-embedding is the process of calibrating the ports. Each port in a circuit analyzed by em introduces a discontinuity into the analysis results. In addition, any feed transmission lines that might be present introduce phase shift, and possibly, impedance mismatch and loss. De-embedding is the process by which the port discontinuity and feed transmission lines are negated from the analysis results. The process of negating lengths of transmission line during de-embedding is known as “shifting reference planes”. Sonnet defines a reference plane to indicate the length of feed transmission line you wish to have negated during de-embedding. For a full discussion of de-embedding, please refer to De‑embedding in the Sonnet User’s Guide.

87.  While still on metal level 3, zoom into the two stubs at the bottom of the inductor.

You will add a port and feedline to each of these stubs.

88.  Select Insert -  Feedline from the main menu in the project editor window.

The appearance of the cursor changes to indicate you are in Add Feedline mode.

89.  Move the cursor over the end of the left stub until the end of the stub is highlighted with a blue line.

The blue line indicates the polygon edge from which the feedline will be extended to the boxwall.

90.  Click to add the feedline and port.

The first feedline, port and reference plane are added to your circuit as shown below.  A standard port is added at the end of the feedline on the boxwall with a reference plane set such that it de–embeds the added feedline.

91.  Repeat the procedure and add a feedline to the right stub.
92.  Click on the Full View  button in the project editor tool bar.

This zooms out to a full view of your circuit, which should appear similar to the picture below.

93.  Click on the Metal4 Technology Layer in the stackup manager.

The view updates to level 9. The center tap line is on this metal level.

94.  In a similar manner, using the Insert ⇒  Feedline command, you should add a feedline, port and reference plane to the center tap line.

When you are done, the view on metal level 9 should be as shown below. The length of the reference plane for Port 3 is 300 microns.

This completes the post-import editing.

95.  Select File ⇒ Save from the project editor main menu to save the file before continuing.

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