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Computing the Frequency Response of a Filter

The freqz2 function computes the frequency response for a two-dimensional filter. With no output arguments, freqz2 creates a mesh plot of the frequency response. For example, consider this FIR filter,

This command computes and displays the 64-by-64 point frequency response of h.

Frequency Response of a Two-Dimensional Filter

To obtain the frequency response matrix H and the frequency point vectors f1 and f2, use output arguments

freqz2 normalizes the frequencies f1 and f2 so that the value 1.0 corresponds to half the sampling frequency, or pi radians.

For a simple m-by-n response, as shown above, freqz2 uses the two-dimensional fast Fourier transform function fft2. You can also specify vectors of arbitrary frequency points, but in this case freqz2 uses a slower algorithm.

See Fourier Transform for more information about the fast Fourier transform and its application to linear filtering and filter design.

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