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In control theory and signal processing, a linear, time-invariant system is said to be minimum-phase if the system and its inverse are causal and stable.〔J. O. Smith III, ''(Introduction to Digital Filters with Audio Applications )'' (September 2007 Edition).〕 For example, a discrete-time system with rational transfer function can only satisfy causality and stability requirements if all of its poles are inside the unit circle. However, we are free to choose whether the zeros of the system are inside or outside the unit circle. A system with rational transfer function is minimum-phase if all its zeros are also inside the unit circle. Insight is given below as to why this system is called minimum-phase. == Inverse system == A system is invertible if we can uniquely determine its input from its output. I.e., we can find a system such that if we apply followed by , we obtain the identity system . (See Inverse matrix for a finite-dimensional analog). I.e., : Suppose that is input to system and gives output . : Applying the inverse system to gives the following. : So we see that the inverse system allows us to determine uniquely the input from the output . 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「minimum phase」の詳細全文を読む スポンサード リンク
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