ZyXEL Communications PLA-470 V2 - V3.0.5 Instalační příručka stáhnout pdf (Strana 160)

Coupling

In the electrical field, coupling can be defined as how two electrical circuits connect

together in order to generate an electron flow between these two circuits. This electron

flow is conveyed by an electric and a magnetic field created between the two electrical cir-

cuits due to their inductive and capacitive nature.

Inductive coupling is much more efficient than capacitive coupling. It uses the

electromagnetic induction method between two electrical wirings or between an

electrical wiring and a coil wound around this wiring. An inductive coupler reduces

the attenuation by 10 to 15 dB for some frequencies in comparison with a capacitive

coupler. The attenuation between the outlet and the switch box varies from 10 to 30

dB. It is maximum between 15 MHz and 20 MHz.

In the field of PLC networks, the injectors are devices used to connect a PLC

device to the electrical network via an inductive coupling directly around electrical

wirings, for example, at the level of the electrical switchboard of a building.

Figure 7.23 illustrates the principle of a PLC signal injector consisting of the

two following elements:

•

A magnetic coil wound around the neutral cable of the electrical network. As

we’ll see in chapters 11 and 12, the neutral cable is the most interesting cable

for the injection of the PLC signal over an electrical network, since it is distrib-

uted over all the electrical equipment.

•

A cable TV modem connected by a cable (for example, a coaxial cable) to the

magnetic coil.

Methods for Accessing the Medium 141

Figure 7.23 PLC signal injection by inductive coupling with a coil over a single-phase network

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ZyXEL Communications PLA-470 V2 - V3.0.5 Instalační příručka Strana 160