GBLACKMANHARRIS

Purpose:

Generates a 4 term Blackman-Harris Window.

Syntax:

GBLACKMANHARRIS(N, spacing, "sym")

An integer, the number of points to generate.

spacing

A real, the spacing (delta x) between points.

"sym"

Optional. A string, the symmetry flag.

"symmetric"	:	Starting and ending points are equal (default).
"periodic"	:	Periodically extended window. Conforms to ISO standard.
"iso"	:	Same as "periodic".

Returns:

A series.

Example:

W1: gblackmanharris(100, .01)

generates a 100-point symmetric Blackman-Harris window using the following 4 term formula:

where n is the n^th point (1 <= n <= N) and N is 100, the number of points. The spacing between samples is set to 0.01.

Example:

W2: gblackmanharris(100, 0.01, "periodic")

Creates a 100 point periodic Blackman-Harris window that conforms to the ISO 18431-1 standard.

where n is the n^th point (1 <= n <= N) and N is the number of points to generate. The spacing between samples is set to 0.01.

Remarks:

The "sym" flag controls the window symmetry as follows:

"Symmetric" sets the last point to be the same value as the first point. For an N point symmetric window, a N-1 point periodic window is effectively created and the N^th point is set to the same value as the first point.

"Periodic" or "iso" creates a periodic window function useful in spectrum analysis applications. "Periodic" or "iso" conforms to the ISO 18431-1 standard for windowing functions.

The Hamming, Hanning, Flattop and Blackman windows are part of the family of cosine window functions. The ISO 18431-1 standard periodic form of these windowing functions are defined by:

where K is the number of window coefficients and N is the length of the window. The symmetric form of the window can be constructed by setting N to N-1.

For the Blackman-Harris window:

Use the BLACKMANHARRIS function command to automatically create and multiply a Blackman-Harris window with a series. For example:

blackmanharris(W1)

multiplies Window 1 with a Blackman-Harris window of the same length and spacing as the series in W1.

See GBLACKMAN to generate a 3 term Blackman window.

Blackman, Blackman-Harris, Flattop, Hamming, Hanning and Kaiser Windows are useful in creating FIR filters and in preprocessing series for FFT calculations.

GBLACKMANHARRIS

Purpose:

Syntax:

Returns:

Example:

Example:

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See Also: