ABSTRACT
The measurement of phase is important in almost all applications where sinusoids proliferate. Many means have therefore been devised for this measurement. One of the most obvious measurement techniques is to directly measure the fractional part of the period that has been completed on a cathode-ray oscilloscope (CRO). Another approach, which is particularly useful when a significant amount of noise is present, is to take the Fourier transform of the signal. According to Fourier theory, for a sinusoidal signal, the energy in the Fourier transform is concentrated at the frequency of the signal; the initial phase of the signal (i.e., the phase at time,
t
= 0) is the phase of the Fourier transform at the point of this energy concentration. The measurements of initial phase and frequency obtained from the Fourier transform can then be used to deduce the phase of the signal for any value of time.
