abstract
| - The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0.
- The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0. Phase is a frequency domain or Fourier transform domain concept, and as such, can be readily understood in terms of simple harmonic motion. The same concept applies to wave motion, viewed either at a point in space over an interval of time or across an interval of space at a moment in time. Simple harmonic motion is a displacement that varies cyclically, as depicted below: and described by the formula: where A is the amplitude of oscillation, f is the frequency, t is the elapsed time, and is the phase of the oscillation. The phase determines or is determined by the initial displacement at time t = 0. A motion with frequency f has period Two potential ambiguities can be noted:
* One is that the initial displacement of is different than the sine function, yet they appear to have the same "phase".
* The time-variant angle or its modulo value, is also commonly referred to as "phase". Then it is not an initial condition, but rather a continuously-changing condition. The term instantaneous phase is used to distinguish the time-variant angle from the initial condition. It also has a formal definition that is applicable to more general functions and unambiguously defines a function's initial phase at t=0. I.e., sine and cosine inherently have different initial phases. When not explicitly stated otherwise, cosine should generally be inferred. (also see phasor)
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