Editing Cutoff frequency (section)

{{Short description|Frequency response boundary}}
[[File:Bandwidth.svg|thumb|right|320px|Magnitude transfer function of a [[bandpass filter]] with lower 3&nbsp;dB cutoff frequency ''f''<sub>1</sub> and upper 3&nbsp;dB cutoff frequency ''f''<sub>2</sub>]]
[[File:Butterworth response.svg|right|thumb|320px|[[Bode plot]] (a logarithmic [[frequency response]] plot) of any first-order low-pass filter with a normalized cutoff frequency at <math>\omega</math>=1 and a [[unity gain]] (0 dB) passband.]]

In [[physics]] and [[electrical engineering]], a '''cutoff frequency''', '''corner frequency''', or '''break frequency''' is a boundary in a system's [[frequency response]] at which energy flowing through the system begins to be reduced ([[attenuation|attenuated]] or reflected) rather than passing through.

Typically in electronic systems such as [[Filter (signal processing)|filters]] and [[communication channel]]s, cutoff frequency applies to an edge in a [[lowpass]], [[highpass]], [[bandpass]], or [[band-stop]] characteristic – a frequency characterizing a boundary between a [[passband]] and a [[stopband]]. It is sometimes taken to be the point in the filter response where a [[transition band]] and passband meet, for example, as defined by a [[half-power point]] (a frequency for which the output of the circuit is approximately −3.01&nbsp;[[Decibel|dB]] of the nominal passband value). Alternatively, a stopband corner frequency may be specified as a point where a transition band and a stopband meet: a frequency for which the attenuation is larger than the required stopband attenuation, which for example may be 30&nbsp;dB or 100&nbsp;dB.

In the case of a [[waveguide]] or an [[antenna (radio)|antenna]], the cutoff frequencies correspond to the lower and upper '''cutoff wavelengths'''.