Editing Passband (section)

== Details ==
{{Unreferenced section|date=August 2018}}
In general, there is an inverse relationship between the width of a filter's passband and the time required for the filter to respond to new inputs. Broad passbands yield faster response times.{{Citation needed|date=February 2008}} This is a consequence of the [[mathematics]] of [[Fourier analysis]].

The limiting frequencies of a passband are defined as those at which the relative [[intensity (physics)|intensity]] or [[Power (physics)|power]] decreases to a specified fraction of the maximum intensity or power. This decrease in power is often specified to be the half-power points, ''i.e.'', 3 [[decibel|dB]] below the maximum power.

The difference between the limiting frequencies is called the bandwidth, and is expressed in [[hertz]] (in the optical regime, in nanometers or micrometers of differential wavelength).

The related term "[[bandpass]]" is an adjective that describes a type of filter or filtering process; it is frequently confused with "passband", which refers to the actual portion of affected spectrum. These two words are both [[compound (linguistics)|compound words]] that follow the English rules of formation: the primary meaning is the latter part of the compound, while the modifier is the first part. Hence, one may correctly say 'A dual bandpass filter has two passbands'.