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chebwin(*args, **kwargs)
warning

use scipy.signal.windows.chebwin instead.

Notes

This window optimizes for the narrowest main lobe width for a given order M and sidelobe equiripple attenuation :None:None:`at`, using Chebyshev polynomials. It was originally developed by Dolph to optimize the directionality of radio antenna arrays.

Unlike most windows, the Dolph-Chebyshev is defined in terms of its frequency response:

$$W(k) = \frac{\cos\{M \cos^{-1}[\beta \cos(\frac{\pi k}{M})]\}} {\cosh[M \cosh^{-1}(\beta)]}$$

where

$$\beta = \cosh \left [\frac{1}{M}\cosh^{-1}(10^\frac{A}{20}) \right ]$$

and 0 <= abs(k) <= M-1. A is the attenuation in decibels (:None:None:`at`).

The time domain window is then generated using the IFFT, so power-of-two M are the fastest to generate, and prime number M are the slowest.

The equiripple condition in the frequency domain creates impulses in the time domain, which appear at the ends of the window.

Parameters

M : int

Number of points in the output window. If zero or less, an empty array is returned.

at : float

Attenuation (in dB).

sym : bool, optional

When True (default), generates a symmetric window, for use in filter design. When False, generates a periodic window, for use in spectral analysis.

Returns

w : ndarray

The window, with the maximum value always normalized to 1

Return a Dolph-Chebyshev window.

Examples

Plot the window and its frequency response:

>>> from scipy import signal
... from scipy.fft import fft, fftshift
... import matplotlib.pyplot as plt
>>> window = signal.windows.chebwin(51, at=100)
... plt.plot(window)
... plt.title("Dolph-Chebyshev window (100 dB)")
... plt.ylabel("Amplitude")
... plt.xlabel("Sample")
>>> plt.figure()
... A = fft(window, 2048) / (len(window)/2.0)
... freq = np.linspace(-0.5, 0.5, len(A))
... response = 20 * np.log10(np.abs(fftshift(A / abs(A).max())))
... plt.plot(freq, response)
... plt.axis([-0.5, 0.5, -120, 0])
... plt.title("Frequency response of the Dolph-Chebyshev window (100 dB)")
... plt.ylabel("Normalized magnitude [dB]")
... plt.xlabel("Normalized frequency [cycles per sample]")
See :

Back References

The following pages refer to to this document either explicitly or contain code examples using this.

scipy.signal.windows._windows.taylor

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GitHub : /scipy/signal/__init__.py#357
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