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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 quadrature modulation ： ウィキペディア英語版 quadrature modulation Quadrature modulation is the general technique of modulating two carriers. Examples include Quadrature amplitude modulation, Phase-shift keying, and Minimum-shift keying. Constellation diagrams are used to examine the modulation in the 2-D signal space. == Explanation == Sending a signal by amplitude modulation consists of sending the function :$y(t)\; =\; I(t)\; \backslash cdot\; \backslash cos(\backslash omega\_c\; t)$ where $I(t)$ is the signal to encode and $\backslash cos(\backslash omega\_c\; t)$ is the carrier wave, $\backslash omega\_c$ is the carrier frequency – one is changing the amplitude of a carrier wave to encode the signal, hence amplitude modulation. In general one could also change the phase of the carrier to encode the signal, as in: :$z(t)\; =\; I(t)\; \backslash cdot\; \backslash cos(\backslash omega\_c\; t)\; -\; Q(t)\; \backslash cdot\; \backslash sin(\backslash omega\_c\; t)$ this 90° (the angle of a rectangle, or a 1/4 turn) is why it is called "quadrature" modulation, and the symbols $I(t)$ and $Q(t)$ indicate the "in-phase" signal and "quadrature" signal. In terms of Euler's formula, $e^\; =\; \backslash cos\; t\; +\; i\; \backslash sin\; t,$ amplitude modulation encodes a 1-dimensional ''real'' signal, while quadrature modulation encodes a 2-dimensional ''complex'' signal. This viewpoint, that a wave of a given frequency can encode 2 dimensions of data, is elaborated in Fourier analysis, and is the principle that quadrature modulation exploits. 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「quadrature modulation」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.