What is the 'periodic' sampling option in the HAMMING function used for in Signal Processing Toolbox 6.2 (R14)?

The HAMMING window function has a secondary argument named 'sflag', which can take on two values: 'symmetric' or 'periodic'. The HANN, BLACKMAN, and FLATTOPWIN functions also have the option to create a 'periodic' window. I would like to know more details regarding the usefulness of the 'periodic' option.

Answer 1

[MathWorks Support Team]

This enhancement has been incorporated in Release 2006b (R2006b). For previous product releases, read below for any possible workarounds:

Documentation on the HAMMING, HANN, BLACKMAN, and FLATTOPWIN function is missing information about the 'periodic' option. Here is some additional information:

The periodic flag is useful for DFT/FFT purposes such as in spectral analysis.

Because there is an implicit periodic extension in the DFT/FFT, the periodic flag enables a signal that is windowed with a periodic window to have perfect periodic extension. When using windows for spectral analysis or other DFT/FFT purposes, the periodic option can be useful. When using windows for filter design, the symmetric flag should be used.

Please refer to the following for more information:

Harris, F., "On the use of windows for harmonic analysis with the discrete Fourier transform" Proceedings of the IEEE , vol. 66, No. 1, January 1978.