Linear circuits - Parametric representation

Consider a two-port circuit (a two-terminal "input" port, and a two-terminal "output" port) containing no independent sources. How can we model the circuit's behavior with respect to the outside world? We show that we can define several sets of four parameters that fully characterize the circuit, known as a quadripole, independently of any circuits connected to the "input" and "output" ports. At high frequencies, it is interesting to characterize the quadrupole by a particular set of parameters: the S-parameters (or distribution parameters).

It is also possible to represent any disturbance sources internal to the quadrupole as sources external to it (allowing, for example, the simple study of the influence of noise in electronic components).

Different quadripoles can be combined to form a new quadripole involved, for example, in a transmission chain, which can be characterized by a transfer function, an input impedance and an output impedance.

This notion of parametric representation can easily be extended to multi-access (multi-pole) circuits.

This last article develops all these notions.

The set of articles on electrical circuits comprises three parts:

• [E100v2] Linear electric circuits. Definitions and theorems ;

• [E102v2] Linear electric circuits. Analysis methods and energy considerations ;

• [E104v2], Linear electric circuits. Parametric representation.