AttenuationdB

AttenuationdB, commonly called attenuation in decibels, is a logarithmic unit used to express the reduction of a signal as it travels through a medium or component. It quantifies how much power, voltage, or current is lost between a reference point and a downstream point in a system. For power, attenuation in decibels is defined as A_dB = 10 log10(Pin/Pout), which is equivalently A_dB = -10 log10(Pout/Pin). When impedance remains constant, the same idea applies to voltage or current measurements: A_dB = 20 log10(Vin/Vout) or A_dB = 20 log10(Iin/Iout).

AttenuationdB is used across fields such as telecommunications, audio engineering, RF systems, and optical fibers. In fiber optics, for example, attenuation is often expressed as dB per kilometer (dB/km) to describe how much signal is lost over distance. In electrical networks, insertion loss and channel loss are described in dB to reflect practical signal degradation through cables, connectors, filters, or amplifiers. Attenuation values are inherently nonnegative when stated as loss; negative values would imply amplification.

Measurement of attenuation typically uses calibrated instruments such as power meters, network or spectrum analyzers, or optical power meters, sometimes in conjunction with reference measurements to compute the dB ratio. Proper budgeting of link performance relies on accurately knowing attenuationdB to ensure sufficient signal-to-noise ratio at the receiver.