Electrical Engineering ⇒ Topic : Z-parameters

PARAMETERS

z-parameters also known as open circuit impedance parameters. In z-parameters, the input and output voltages for two-port network, i.e., V₁ and V₂, are expressed in terms of the input and

output currents. From Figure D.1, it can be written as:

                   V₁ = Z₁₁I₁ + Z₁₂I₂                                  ..........(1)

            and V₂ = Z₂₁I₁ + Z₂₂I₂                                  ...........(2)

From Eqs. (1) and (2), it can be written as:

                                         ............ (3)

where Z₁₁, Z₁₂, Z₂₁, and Z₂₂ are known as z-parameters of the two-port network shown in Figure (1).

Assuming I₂ = 0, i.e., output port as open circuit, it can be written as:

                                    .............. (4)

                               ................ (5)

Assuming /₁ = 0, i.e., input port as open circuit, it can be written as:

                                   .................... (6)

                                   ..................... (7)

Z₁₁ and Z₂₂ are known as input and output impedances when output and input ports are open-circuited. Z₁₂ and Z₂₁ are known as reverse and forward transfer impedances when output and input ports are open-circuited.

(For symmetry, Z₁₂ = Z₂₁ and for reciprocity Z₁₂ = Z₂₂.)