In addition, there are also places to use animal symbols like three no-evil monkeys. S-parameters are used at frequencies where the ports are often coaxial or waveguide connections.Animal emoji symbols are very popular in WhatsApp or Facebook Messenger chat conversations. Ports are usually pairs of terminals with the requirement that the current into one terminal is equal to the current leaving the other. Ports are the points at which electrical signals either enter or exit the network. It may also include many typical communication system components or 'blocks' such as amplifiers, attenuators, filters, couplers and equalizers provided they are also operating under linear and defined conditions.Īn electrical network to be described by S-parameters may have any number of ports. The network is characterized by a square matrix of complex numbers called its S-parameter matrix, which can be used to calculate its response to signals applied to the ports.įor the S-parameter definition, it is understood that a network may contain any components provided that the entire network behaves linearly with incident small signals.
In the S-parameter approach, an electrical network is regarded as a ' black box' containing various interconnected basic electrical circuit components or lumped elements such as resistors, capacitors, inductors and transistors, which interacts with other circuits through ports. A variant of the latter is the pseudo-traveling-wave S-parameters. In his seminal paper, Kurokawa clearly distinguishes the power-wave S-parameters and the conventional, traveling-wave S-parameters. The latter was popularized by Kaneyuki Kurokawa, who referred to the new scattered waves as 'power waves.' The two types of S-parameters have very different properties and must not be mixed up. A different kind of S-parameters was introduced in the 1960s. In these S-parameters and scattering matrices, the scattered waves are the so-called traveling waves. The term scattering matrix was used by physicist and engineer Robert Henry Dicke in 1947 who independently developed the idea during wartime work on radar.
The name used by Belevitch was repartition matrix and limited consideration to lumped-element networks. The first published description of S-parameters was in the thesis of Vitold Belevitch in 1945. S-parameters are readily represented in matrix form and obey the rules of matrix algebra. S-parameters change with the measurement frequency, so frequency must be specified for any S-parameter measurements stated, in addition to the characteristic impedance or system impedance. S-parameters in common use - the conventional S-parameters - are linear quantities (not power quantities, as in the below mentioned 'power waves' approach by Kaneyuki Kurokawa). This is equivalent to the wave meeting an impedance differing from the line's characteristic impedance.Īlthough applicable at any frequency, S-parameters are mostly used for networks operating at radio frequency (RF) and microwave frequencies. In the context of S-parameters, scattering refers to the way in which the traveling currents and voltages in a transmission line are affected when they meet a discontinuity caused by the insertion of a network into the transmission line. The term 'scattering' is more common to optical engineering than RF engineering, referring to the effect observed when a plane electromagnetic wave is incident on an obstruction or passes across dissimilar dielectric media. Many electrical properties of networks of components ( inductors, capacitors, resistors) may be expressed using S-parameters, such as gain, return loss, voltage standing wave ratio (VSWR), reflection coefficient and amplifier stability. Modern vector network analyzers measure amplitude and phase of voltage traveling wave phasors using essentially the same circuit as that used for the demodulation of digitally modulated wireless signals. Contrary to popular belief, the quantities are not measured in terms of power (except in now-obsolete six-port network analyzers). These terminations are much easier to use at high signal frequencies than open-circuit and short-circuit terminations. They differ from these, in the sense that S-parameters do not use open or short circuit conditions to characterize a linear electrical network instead, matched loads are used. The S-parameters are members of a family of similar parameters, other examples being: Y-parameters, Z-parameters, H-parameters, T-parameters or ABCD-parameters. The parameters are useful for several branches of electrical engineering, including electronics, communication systems design, and especially for microwave engineering. Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals. Values which describe behavior of a linear electric circuit
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