Single Feed Line

Continuing with the boxwall port example, the figure below shows a circuit with a length of transmission line, TRL, inserted between a box-wall port and the device under test.

When the circuit has a reference plane, em negates the transmission line in a manner similar to that used to remove the port discontinuity. Em calculates S-parameters for the line alone, and then cascades a “negative” line along with negative R and C as illustrated in the next figure.