dBbandbreedte

dB bandbreedte, or decibel bandwidth, is a measure of the frequency range over which a system or component operates within a specified attenuation level, expressed in decibels (dB). It is commonly used to characterize electronic filters, amplifiers, oscillators, antennas, and optical devices. The bandwidth is defined as the difference between the upper and lower frequencies where the output signal falls to a particular dB value relative to its maximum. The most frequently cited threshold is the −3 dB point, which corresponds to the frequency at which the output power has dropped to half its maximum value. For a simple RC low‑pass filter, the −3 dB frequency is given by f=1/(2πRC).

Other dB specifications are also used, such as the −10 dB or −20 dB bandwidth, especially when a steeper roll‑off is required. In optical communications, the dB bandwidth can describe the spectral width of a laser or the frequency response of an optical modulator, using the same principle of measuring the drop in power relative to the peak. The dB bandbreedte is a convenient unit because it accommodates a wide range of signal levels on a logarithmic scale, allowing easy comparison between devices with vastly different power outputs. Because the measure is dependent on a chosen reference point, it is always specified in the context of the particular dB threshold used.