Exact calibration of multiple coupled internal ports in electromagnetic analysis

It can be inconvenient or impossible to analyze a complete circuit in a single electromagnetic (EM) analysis. In these cases, internal ports may be used so that data for difficult portions of the circuit can be inserted at a later time. Examples include surface mount devices (SMD) and active devices such as transistors. While most electromagnetic analyses allow internal ports, such ports are rarely calibrated. This leaves in place the electromagnetic fringing fields surrounding any internal ports. These fields are an artifact of the EM analysis not present in the actual structure. They take the form of excess fringing capacitances and inductances. This paper describes a technique for exactly removing (i.e., de-embedding) these fringing fields leaving perfectly calibrated internal ports. This allows internal ports to be used in sensitive situations for which they were previously unavailable.