Common-mode signal is the component of an analog signal which is present with one sign on all considered conductors. In telecommunication, common-mode signal on a transmission line is known as longitudinal voltage.
In electronics where the signal is transferred with differential voltage use, the common-mode signal is called a half-sum of voltages:
When referenced to the local common or ground, a common-mode signal appears on both lines of a two-wire cable, in-phase and with equal amplitudes. Technically, a common-mode voltage is one-half the vector sum of the voltages from each conductor of a balanced circuit to local ground or common. Such signals can arise from one or more of the following sources: Radiated signals coupled equally to both lines, An offset from signal common created in the driver circuit, or A ground differential between the transmitting and receiving locations.
Common-mode signals may be effectively eliminated by using differential amplifiers or receivers that respond only to voltage differences, e.g., those between the wires that constitute a pair. Induced common-mode signals at low (power-line) frequencies can be greatly reduced by twisting parallel wires to create twisted wire pairs.
Famous quotes containing the word signal:
“Perhaps having built a barricade when you’re sixteen provides you with a sort of safety rail. If you’ve once taken part in building one, even inadvertently, doesn’t its usually latent image reappear like a warning signal whenever you’re tempted to join the police, or support any manifestation of Law and Order?”
—Jean Genet (1910–1986)