- Center frequency
In
electrical engineering andtelecommunications , 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 thearithmetic mean or thegeometric 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 thefrequency response is constructed to be symmetric on a logarithmic frequency scale. [cite book | title = CRC Handbook of Electrical Filters | author = John T. Taylor and Qiuting Huang | publisher = CRC Press | isbn = 0849389518 | year = 1997| url = http://books.google.com/books?id=HtyKSVF6zPsC&pg=PA57&ots=3n1Qvbs5Me&dq=center+frequency+bandpass+%22geometric+mean%22&as_brr=3&sig=FKeDPjh1YZ8AjDUK1WTu9ezr3p8#PPA57,M1] The geometric center frequency corresponds to a mapping of the DC response of the prototype lowpass filter, which is aresonant frequency sometimes equal to the peak frequency of such systems, for example as in aButterworth 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 asfrequency-division multiplexing . [cite book | title = Fiber Optics Illustrated Dictionary | author = Julie K. Petersen | isbn = 084931349X | year = 2003 | publisher = CRC Press | url = http://books.google.com/books?id=AcGFlqSqNEUC&pg=PA100&ots=xJ2Rd91Ovh&dq=center+frequency+bandpass+%22arithmetic+mean%22+fdm&sig=cOaKer3Z6218tzEbEnss8Gj7mr4]ee also
*
Band-pass filter References
External links
* [http://www.sengpielaudio.com/calculator-geommean.htm Calculations and comparisons between the geometric mean and the arithmetic mean]
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