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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Bessel filter ： ウィキペディア英語版 Bessel filter In electronics and signal processing, a Bessel filter is a type of analog linear filter with a maximally flat group/phase delay (maximally linear phase response), which preserves the wave shape of filtered signals in the passband. Bessel filters are often used in audio crossover systems. The filter's name is a reference to German mathematician Friedrich Bessel (1784–1846), who developed the mathematical theory on which the filter is based. The filters are also called Bessel–Thomson filters in recognition of W. E. Thomson, who worked out how to apply Bessel functions to filter design.〔Thomson, W.E., "Delay Networks having Maximally Flat Frequency Characteristics", ''Proceedings of the Institution of Electrical Engineers'', Part III, November 1949, Vol. 96, No. 44, pp. 487–490.〕 The Bessel filter is very similar to the Gaussian filter, and tends towards the same shape as filter order increases.〔http://www.robots.ox.ac.uk/~sjrob/Teaching/SP/l3.pdf〕〔http://www.dsprelated.com/showmessage/130958/1.php〕 The Bessel filter has better shaping factor, flatter phase delay, and flatter group delay than a Gaussian of the same order, though the Gaussian has lower time delay.〔Design and Analysis of Analog Filters: A Signal Processing Perspective By Larry D. Paarmann p 238 http://books.google.com/books?id=l7oC-LJwyegC〕 The time-domain step response of the Bessel filter has some overshoot, but less than common frequency domain filters. == The transfer function == A Bessel low-pass filter is characterized by its transfer function:〔 〕 :$H(s)\; =\; \backslash frac\backslash ,$ where $\backslash theta\_n(s)$ is a reverse Bessel polynomial from which the filter gets its name and $\backslash omega\_0$ is a frequency chosen to give the desired cut-off frequency. The filter has a low-frequency group delay of $1\; /\; \backslash omega\_0$. Since $\backslash theta\_n\; (0)$ is indeterminate by the definition of reverse Bessel polynomials, but is a removable singularity, it is defined that $\backslash theta\_n\; (0)\; =\; \backslash lim\_\; \backslash theta\_n\; (x)$. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Bessel filter」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.