Fase (galura): Béda antarrépisi

'''Waves''' are amplitudes that change cyclically, often modeled as sinusoidal functions of time (t) or some other variable. Consider the ever-changing angle''':'''

where <math>A\,</math>, <math>f\,</math>, and <math>\theta\,</math> are constants, and '''mod''' is the [[Modulo_operation|Modulo operation]].

The initial ''phase'' (at t=0) of this sinusoid is <math>\varphi(0) = \theta\,</math>, which is also commonly referred to as just "phase". The instantaneous phase at time t is <math>2 \pi f t + \theta \,</math>, which has units of radians. &nbsp; <math>t\,</math> has units of seconds, so <math>f\,</math> has units of '''cycles''' <math>[= 2 \pi </math> radians <math>= 360</math> degrees<math>]</math> '''per second''', which represents the '''frequency''' of the oscillations. Frequency defines (or reflects) the rate at which the instantaneous phase changes. The duration of one cycle of the wave, called its ''period'', is given by''':''' <math>T = 1/f \,</math> (seconds per cycle).

When <math>\theta\,</math> is referred to as ''the phase'' or ''phase shift'', the implied reference is''':''' <math>2 \pi f t\,</math>. For instance, that is what is meant by the "phase" of a [[Fourier transform]] at a particular frequency. The term "phase shift" also has a slightly more general usage, described in the next section.

When the frequency of an oscillation is time invariant, then time is sometimes used (instead of angle) to express instantaneous phase. Thus we measure the rotation of the earth in hours, instead of radians. Time zones are actually a good example of phase shifts. Other measures of phase are''':''' (1) distance, and (2) fraction of the [[wavelength]].

'''Ngagésérna fase''' nyaéta perbédaan atawa parobahan fase dina ''fase awal''. Lamun <math>s(t)\,</math> katunda (ngagésér waktuna) salila <math>\begin{matrix} \frac{1}{4} \end{matrix}\,</math> tina sikleusna, mangka jadi''':'''

numana fase awalna <math>\theta - \begin{matrix}\frac{\pi }{2} \end{matrix}</math>. Ku sabab éta, ngagésérna waktu ékivalén jeung ngagésérna fase. Sabalikna, parobahan fase awal ogé sarua jeung ngagésérna waktu.

[[ImageGambar:Sine waves same phase.png|thumb|360px|right|Galura safase]]

[[ImageGambar:Sine waves different phase.png|thumb|360px|right|Galura henteu safase]]

'''Phase difference''' is similar to ''phase shift'', but more likely to be applied in the context of two signals, particularly when neither is a standard reference. Two waves that have the same frequency and different initial phases, have a phase difference that is constant (independent of t). So it is referred to simply as the '''phase difference''', rather than the initial phase difference or the phase-shift difference. When the phase difference ([[modulo]] 2π) is zero, the waves are said to be '''in phase''' with each other. Otherwise, they are '''out of phase''' with each other. The terms are also commonly hyphenated, and used as an adjective: &nbsp; "The out-of-phase signal caused distortion." If the phase difference is 180 degrees (π radians), then the two signals are said to be ''in antiphase''. And if their peak amplitudes are equal, their sum is zero at all values of time, t.

Communication signals require more complicated forms (than above) of <math>\varphi(t)\,</math>. The linear term is often extracted, and written separately, as follows''':'''

<math>A(t)\,</math> and <math>\varphi(t)\,</math> represent possible [[modulation]] of a pure carrier wave''':''' <math>\cos(2\pi ft)\,</math>. The modulation alters the original <math>\cos\,</math> component of the carrier, and creates a (new) <math>\sin\,</math> component, as shown above. The component that is in phase with the original carrier is referred to as the '''in-phase component'''. The other component, which is always 90° (<math>\begin{matrix} \frac{\pi}{2} \end{matrix}</math> radians) "out of phase", is referred to as the '''quadrature''' component.

[[CategoryKategori:Mékanisme galura]]