Construct flat top window object
sigwin.flattopwin creates a handle to a flat top window object for use in spectral analysis and FIR filtering by the window method. Object methods enable workspace import and ASCII file export of the window values.
H = sigwin.flattopwin returns a flat top window object H of length 64 with symmetric sampling.
H = sigwin.flattopwin(Length) returns a flat top window object of length Length with symmetric sampling. Length must be a positive integer. Entering a positive noninteger value for Length rounds the length to the nearest integer. Entering a 1 for Length results in a window with a single value of 1.
H = sigwin.flattopwin(Length,SamplingFlag) returns a flat top window object H of length Length with sampling SamplingFlag. The SamplingFlag can be either 'symmetric' or 'periodic'.
Flat top window length. Must be a positive integer. Entering a positive noninteger value for Length rounds the length to the nearest integer. Entering a 1 for Length results in a window with a single value of 1.
'symmetric' is the default and forces exact symmetry between the first and second halves of the flat top window. A symmetric window is preferred in FIR filter design.
'periodic' designs a symmetric flat top window of length Length+1 and truncates the window to length Length. This design is preferred in spectral analysis where the window is treated as one period of a Length-point periodic sequence.
|generate||Generates flat top window|
|info||Display information about flat top window object|
|winwrite||Save flat top window in ASCII file|
The following equation defines the flat top window of length N:
where M is N/2 for N even and (N+1)/2 for N odd.
The second half of the symmetric flat top window is obtained by flipping the first half around the midpoint. The symmetric option is the preferred method when using a flat top window in FIR filter design by the window method.
The periodic flat top window is constructed by extending the desired window length by one sample, constructing a symmetric window, and removing the last sample. The periodic version is the preferred method when using a flat top window in spectral analysis because the discrete Fourier transform assumes periodic extension of the input vector.
The coefficients are listed in the following table:
Handle. To learn how copy semantics affect your use of the class, see Copying Objects in the MATLAB® Programming Fundamentals documentation.
Default length N=64 symmetric flat top window:
Generate length N=128 periodic flat top window, return values, and write ASCII file:
H=sigwin.flattopwin(128,'periodic'); % Return window with generate win=generate(H); % Write ascii file in current directory % with window values winwrite(H,'flattopwin_128')
Oppenheim, A.V. and Schafer, R.W. Discrete-time Signal Processing, Upper Saddle River, N.J: Prentice Hall, 1989, pp. 444–447.