Temporary

Given the 2-port network in Fig. 1:

Fig. 1

From the incident/reflected waves, and voltage/current definition:

(1)

and considering the matched termination at port 2:

(2)

therefore the input impedance and the current at each port as a function of the same port voltage are:

(3)

the port 2 parameters can be expressed as a function of port 1 voltage by noticing that:

(4)

hence all port voltages, currents and the total current flowing into the 2-port network I_tot=I₁+I₂ can be expressed as a function of port 1 voltage which is useful when one wants to extract I_tot and this is the current flowing in the shunt branch of a T-network such that the current might not be physically accessible while V₁ and the scattering parameters are generally measurable:

(5)

Notice that in this case (2-port network is simply a shunt Y) from (7) in the section on even/odd mode decomposition of symmetrical networks S₂₁-S₁₁=1 or S₂₁=1+S₁₁ thus (5) reduce to:

(6)

where particularly the first and the last one are intuitive from the shunt configuration forcing the same voltage on both ports.