W_kaisermultiplies the sequence in arrayAby a Kaiser-Bessel window function of parameterpand returns the product in arrayB. ArrayAis unmodified.Pcontrols the width of the central portion of the window; it must be positive, and is usually between 4 and 9. IfNis the number of elements in the arrayAandkis the position in the arrayB, the formula for the window function,wk, is
In the above formula,kranges in value from 0 toN- 1.I0is the modified cylindrical Bessel function of the first kind (seeI0).
Pis often expressed in Kaiser-Bessel window forN=128
terms of a radian frequency parameter,a, using the expression
Errors
W_kaisercauses an HTBasic error if its arguments are not of the types listed in the USAGE section, above, ifpis negative or zero, or ifBcontains fewer elements thanA.
Example
The section on theFftsubroutine contains an example of windowing using theW_kaiserroutine.