|
In electrical engineering, a sinusoid with angle modulation can be decomposed into, or synthesized from, two amplitude-modulated sinusoids that are offset in phase by one-quarter cycle (π/2 radians). All three functions have the same frequency. The amplitude modulated sinusoids are known as in-phase and quadrature components.〔 〕 Some authors find it more convenient to refer to only the amplitude modulation (''baseband'') itself by those terms.〔 〕 ==Definition== In vector analysis, a vector with polar coordinates ''A,φ'' and Cartesian coordinates ''x''=''A''•cos(''φ''), ''y''=''A''•sin(''φ''), can be represented as the sum of orthogonal "components": () + (). Similarly in trigonometry, the expression sin(''x''+''φ'') can be represented by sin(''x'')cos(''φ'') + sin(''x''+''π''/2)sin(''φ''). And in functional analysis, when ''x'' is a linear function of some variable, such as time, these components are sinusoids, and they are orthogonal functions. When ''φ''=0, sin(''x''+''φ'') reduces to just the in-phase component sin(''x'')cos(''φ''), and the quadrature component sin(''x''+''π''/2)sin(''φ'') is zero. We now note that many authors prefer the identity cos(''x''+''φ'') = cos(''x'')cos(''φ'') + cos(''x''+''π''/2)sin(''φ''), in which case cos(''x'')cos(''φ'') is the in-phase component. In both conventions cos(''φ'') is the in-phase amplitude modulation, which explains why some authors refer to it as the actual in-phase component. We can also observe that in both conventions the quadrature component ''leads'' the in-phase component by one-quarter cycle. 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「In-phase and quadrature components」の詳細全文を読む スポンサード リンク
|