The Window Filter Coefficients dialog lets you apply a data window to the Inphase, Quadrature, or Complex Filter. Applying a data window lets you alter the response shape of an existing filter. Therefore, before you can apply a data window, existing filter coefficients must have previously been imported, filled, generated, or designed.

In general, applying a data window tends to deepen stopbands at the cost of broadening passbands. The extent and shape of the broadening/deepening depends on the type of data window selected. The Window Filter Coefficients dialog lets you choose from among the most popular data window types, which are Blackman-Harris - Four Term, Blackman-Harris - Seven Term, Hanning (Cosine), Gaussian, Hamming, and Kaiser-Bessel. The Kaiser-Bessel window includes a parameter called " Alpha" which gives you finer control over the window shape. With an Alpha of " 4" (the default), the Kaiser-Bessel window is very similar to the Blackman-Harris - Four Term window.

For a complete discussion of data windowing issues, see the classic paper by Fredric J. Harris, " On the Use of Windows for Harmonic Analysis with the Discrete Fourier Transform" Proceedings of the IEEE, Vol 66, No. 1, January 1978.