Search results
Results from the WOW.Com Content Network
The group delay, , and phase delay, , are (potentially) frequency-dependent [5] and can be computed from the unwrapped phase shift (). The phase delay at each frequency equals the negative of the phase shift at that frequency divided by the value of that frequency:
The group velocity is positive (i.e., the envelope of the wave moves rightward), while the phase velocity is negative (i.e., the peaks and troughs move leftward). The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the modulation or envelope of the wave—propagates through space.
In signal processing, linear phase is a property of a filter where the phase response of the filter is a linear function of frequency.The result is that all frequency components of the input signal are shifted in time (usually delayed) by the same constant amount (the slope of the linear function), which is referred to as the group delay.
Propagation of a wave packet demonstrating a phase velocity greater than the group velocity. This shows a wave with the group velocity and phase velocity going in different directions. The group velocity is positive, while the phase velocity is negative. [1] The phase velocity of a wave is the rate at which the wave propagates in any medium.
Gain and group delay of the third-order Butterworth filter with = The group delay is defined as the negative derivative of the phase shift with respect to angular frequency and is a measure of the distortion in the signal introduced by phase differences for different frequencies. The gain and the delay for this filter are plotted in the graph ...
A closely related yet independent quantity is the group-delay dispersion (GDD), defined such that group-velocity dispersion is the group-delay dispersion per unit length. GDD is commonly used as a parameter in characterizing layered mirrors, where the group-velocity dispersion is not particularly well-defined, yet the chirp induced after ...
Later, this article mentions negative group delay and that this does not violate causality, which is a big red flag clearly indicating that positive and/or negative group delay (in these passive analog systems, like microphones and loudspeakers) simply cannot be related to time delays (since negative group delay would then imply time advancement).
So, a minimum phase system with all zeros inside the unit circle minimizes the group delay since the group delay of each individual zero is minimized. Illustration of the calculus above. Top and bottom are filters with same gain response (on the left : the Nyquist diagrams , on the right : phase responses), but the filter on the top with a = 0. ...