where h is a line between the terminals at the beginning of the transmission line, and the integration is going from positive (phase)
V to ground. The current is positive going into the terminal at positive
V.
where the integration is taken in the direction of ah × n. This gives the following relation between the transmission line impedance and the surface impedance
where E is the total field and
E0 the incident field, corresponding to the total voltage,
V, and incident voltage,
V0, at the port.