Velocity of Propagation

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Velocity of Propagation

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Rate of flow of electromagnetic radiation, including: </dd>
(a) Phase velocity. The velocity of propagation of surfaces of constant phase. </dd>
Strictly, this definition is applicable only to space periodic fields of infinite length. </dd>
(b) Group velocity. The velocity of propagation of electromagnetic radiant energy in a nondispersive or normally dispersive medium. </dd>
For a complex waveform, group velocity refers to the velocity of propagation of the beats between the component frequencies of the waveform. </dd>
(c) Signal velocity. The velocity of propagation of a signal. </dd>
In a nondispersive or normally dispersive medium, signal and group velocity are the same. For pure CW (continuous-wave) systems, utilizing no modulation, phase velocity is applicable. For systems utilizing modulated CW, signal velocity is applicable. </dd>

References

This article is based on NASA's Dictionary of Technical Terms for Aerospace Use