Does the FREQZ function in the Filter Design Toolbox 2.2 (R13) unwrap the phase angle before plotting?

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MathWorks Support Team 2009-6-27

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I am using FREQZ as indicated by the lines of code below to obtain plots of magnitude and phase versus frequency:

b = [ 0.3125    0.3750    0.3125];
a = 1;
freqz(b,a)

I see a discontinuity in the phase plot. I was wondering if this is due to the phase angle not being unwrapped or if it is due to the choice of the filter coefficients themselves?

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Answer 1

MathWorks Support Team 2009-6-27

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https://ww2.mathworks.cn/matlabcentral/answers/102770-does-the-freqz-function-in-the-filter-design-toolbox-2-2-r13-unwrap-the-phase-angle-before-plottin#answer_112115

The function, FREQZ, successfully plots the unwrapped phase. The UNWRAP function is used in FREQZ.

However, unwrapping the phase does not mean that there cannot be discontinuities in the phase. The ZEROPHASE function can compute a continuous phase response that contains no discontinuities.