In electrical engineering and telecommunications, the center frequency of a filter or channel is a measure of a central frequency between the upper and lower cutoff frequencies. It is usually defined as either the arithmetic mean or the geometric mean of the lower cutoff frequency and the upper cutoff frequency of a band-pass system or a band-stop system.
Typically, the geometric mean is used in systems based on certain transformations of lowpass filter designs, where the frequency response is constructed to be symmetric on a logarithmic frequency scale. The geometric center frequency corresponds to a mapping of the DC response of the prototype lowpass filter, which is a resonant frequency sometimes equal to the peak frequency of such systems, for example as in a Butterworth filter.
The arithmetic definition is used in more general situations, such as in describing passband telecommunication systems, where filters are not necessarily symmetric but are treated on a linear frequency scale for applications such as frequency-division multiplexing.
Famous quotes containing the words center and/or frequency:
“Louise Bryant: Im sorry if you dont believe in mutual independence and free love and respect.
Eugene ONeill: Dont give me a lot of parlor socialism that you learned in the village. If you were mine, I wouldnt share you with anybody or anything. It would be just you and me. Youd be at the center of it all. You know it would feel a lot more like love than being left alone with your work.”
—Warren Beatty (b. 1937)
“The frequency of personal questions grows in direct proportion to your increasing girth. . . . No one would ask a man such a personally invasive question as Is your wife having natural childbirth or is she planning to be knocked out? But someone might ask that of you. No matter how much you wish for privacy, your pregnancy is a public event to which everyone feels invited.”
—Jean Marzollo (20th century)