Ports Attached to Thick Metal May Produce Inaccurate Response Data

Known Bugs - KB-ref: TT5552

Symptoms

When using thick metal in your circuit, attaching a port to the thick metal polygons may cause inaccurate response data.

Cause

When the de-embedding is done on the circuit, the calibration standards do not include the vias which are required to model the thick metal. This may produce inaccurate response data and is more likely to occur as the calibration lengths or reference planes increase in length.

Work around

There are two suggested workarounds for this problem. The first is to use a shorter reference plane or calibration length when analyzing the circuit. But too short of a calibration length or reference planes can also lead to an inaccurate simulation. Therefore, whenever possible, we would recommend using a zero-thickness metal polygon as a feedline to the thick metal polygon and attaching the port to the zero-thickness metal polygon as shown below.