flattopwin

Flat top weighted window

collapse all in page

Syntax

w = flattopwin(L)

w = flattopwin(L,sflag)

w = flattopwin(___,typeName)

Description

w = flattopwin(L) returns an L-point symmetric flat top window

example

w = flattopwin(L,sflag) returns an L-point symmetric flat top window using the window sampling method specified by sflag.

w = flattopwin(___,typeName) specifies the option to return the window w with single or double precision.

Examples

collapse all

Flat Top Window

Open Live Script

Create a 64-point symmetric flat top window. View the result using wvtool.

N = 64;
w = flattopwin(N);
wvtool(w)

$Figure Window Visualization Tool contains 2 axes objects and other objects of type uimenu, uitoolbar, uipanel. Axes object 1 with title Time domain, xlabel Samples, ylabel Amplitude contains an object of type line. Axes object 2 with title Frequency domain, xlabel Normalized Frequency (\times\pi rad/sample), ylabel Magnitude (dB) contains an object of type line.$

Input Arguments

collapse all

`L` — Window length
positive integer

Window length, specified as a positive integer.

Note

If you specify L as noninteger, the function rounds it to the nearest integer value.

`sflag` — Window sampling
`"symmetric"` (default) | `"periodic"`

Window sampling method, specified as:

"symmetric" — Use this option when using windows for filter design.
"periodic" — This option is useful for spectral analysis because it enables a windowed signal to have the perfect periodic extension implicit in the discrete Fourier transform. When 'periodic' is specified, the function computes a window of length L + 1 and returns the first L points.

Data Types: char | string

`typeName` — Output data type
`"double"` (default) | `"single"`

Since R2024b

Output data type (class), specified as one of these:

"double" — Use this option to return a double-precision output w.
"single" — Use this option to return a single-precision output w.

Data Types: char | string

Output Arguments

collapse all

`w` — Flat top window
column vector

Flat top window, returned as a column vector.

Algorithms

Flat top windows are summations of cosines. The coefficients of a flat top window are computed from the following equation:

$w (n) = a_{0} - a_{1} \cos (\frac{2 π n}{L - 1}) + a_{2} \cos (\frac{4 π n}{L - 1}) - a_{3} \cos (\frac{6 π n}{L - 1}) + a_{4} \cos (\frac{8 π n}{L - 1}),$

where $0 \leq n \leq L - 1$ . The coefficient values are:

Coefficient	Value
a₀	0.21557895
a₁	0.41663158
a₂	0.277263158
a₃	0.083578947
a₄	0.006947368

Flat top windows have very low passband ripple (< 0.01 dB) and are used primarily for calibration purposes. Their bandwidth is approximately 2.5 times wider than a Hann window.

References

[1] D’Antona, Gabriele, and A. Ferrero. Digital Signal Processing for Measurement Systems. New York: Springer Media, 2006, pp. 70–72.

[2] Gade, Svend, and Henrik Herlufsen. “Use of Weighting Functions in DFT/FFT Analysis (Part I).” Windows to FFT Analysis (Part I): Brüel & Kjær Technical Review. Vol. x, Number 3, 1987, pp. 1–28.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Version History

Introduced before R2006a

expand all

R2024b: Generate Single-Precision Outputs

The flattopwin function supports single-precision outputs.

R2024a: `flattopwin` supports GPU code generation

The flattopwin function supports code generation for graphical processing units (GPUs). You must have MATLAB^® Coder™ and GPU Coder™ to generate CUDA^® code.

flattopwin

Syntax

Description