Signal Processing Toolbox

Delay

The group delay of a filter is a measure of the average delay of the filter as a function of frequency. It is defined as the negative first derivative of a filter's phase response. If the complex frequency response of a filter is , then the group delay is

where is the phase angle of . Compute group delay with

• [gd,w] = grpdelay(b,a,n)
  

which returns the n-point group delay, , of the digital filter specified by b and a, evaluated at the frequencies in vector w.

The phase delay of a filter is the negative of phase divided by frequency:

To plot both the group and phase delays of a system on the same FVTool graph, type

• [b,a] = butter(10,200/1000); 
  hFVT = fvtool(b,a,'Analysis','grpdelay'); 
  set(hFVT,'NumberofPoints',128,'OverlayedAnalysis','phasedelay')
  ; 
  legend(hFVT)
  
  
  

Magnitude and Phase

Zero-Pole Analysis

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