phase

The shift of a periodic signal, often measured referenced to its zero crossing, compared to a reference signal of the same frequency. One period of the signal is defined as having a duration of 360 degree of 2 pi radians.

It should be noted that the phase shift is often related to as a time delay. However, since phase shifts occur in both the positive and negative direction, great caution should be used in directly relating phase shift to a time shift. Many forms of apparent time shift of a waveform are actually due to a distortion of the waveform. For example, a high pass filter has a positive phase shift below its lower cut-off frequency, hence giving the illusion that the signal comes out of the circuit before it is put into it.

Often the slope of the phase curve, known as the group delay, is used to characterize the delay of a circuit. Group delay can be measured using the phase portion of the frequency response function.

Click on Tutorial for a more detailed description of phase and phase modulation.

Units:

rad or degrees

1 ratings | 4.00 out of 5

Print

Reader Comments | Submit a comment »