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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 Linear phase ： ウィキペディア英語版 Linear phase Linear phase is a property of a filter, where the phase response of the filter is a linear function of frequency. The result is that all frequency components of the input signal are shifted in time (usually delayed) by the same constant amount, which is referred to as the phase delay. And consequently, there is no phase distortion due to the time delay of frequencies relative to one another. For discrete-time signals, perfect linear phase is easily achieved with a finite impulse response (FIR) filter.  Approximations can be achieved with infinite impulse response (IIR) designs, which are more computationally efficient.  Several techniques are: * a Bessel transfer function which has a maximally flat group delay * a maximally flat group delay approximation function * a phase equalizer == Examples == When a sinusoid$,\backslash \; \backslash sin(\backslash omega\; t\; +\; \backslash theta),$  passes through a filter with group delay $\backslash tau,$  the result is: :$A(\backslash omega)\backslash cdot\; \backslash sin(\backslash omega\; (t-\backslash tau)\; +\; \backslash theta)\; =\; A(\backslash omega)\backslash cdot\; \backslash sin(\backslash omega\; t\; +\; \backslash theta\; -\; \backslash omega\; \backslash tau),$ where: *$A(\backslash omega)$ is a frequency-dependent amplitude multiplier. *The phase shift $\backslash omega\; \backslash tau$ is a linear function of frequency (ω), and $-\backslash tau$ is the slope. For linear phase, it is sufficient to have that property only in the passband(s) of the filter, where |A(ω)| has relatively large values. Therefore both magnitude and phase graphs (Bode plots) are customarily used to examine a filter's linearity. A "linear" phase graph may contain discontinuities of π and/or 2π radians. The smaller ones happen where A(ω) changes sign. Since |A(ω)| cannot be negative, the changes are reflected in the phase plot. The 2π discontinuities happen because of plotting the principal value of $\backslash omega\; \backslash tau,$  instead of the actual value. In discrete-time applications, one only examines the region of frequencies between 0 and the Nyquist frequency, because of periodicity and symmetry. Depending on the frequency units, the Nyquist frequency may be 0.5, 1.0, π, or ½ of the actual sample-rate.  Some examples of linear and non-linear phase are shown below. A filter with linear phase may be achieved by an FIR filter which is either symmetric or anti-symmetric.  A necessary but not sufficient condition is: :$\backslash sum\_^\backslash infty\; h()\; \backslash cdot\; \backslash sin(\backslash omega\; \backslash cdot\; (n\; -\; \backslash alpha)\; +\; \backslash beta)=0$ for some $\backslash alpha,\; \backslash beta$. 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「Linear phase」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.