Source code for deltasigma._ds_hann

# -*- coding: utf-8 -*-
# This module provides the ds_hann function.
# Copyright 2013 Giuseppe Venturini
# This file is part of python-deltasigma.
# python-deltasigma is a 1:1 Python replacement of Richard Schreier's
# MATLAB delta sigma toolbox (aka "delsigma"), upon which it is heavily based.
# The delta sigma toolbox is (c) 2009, Richard Schreier.
# python-deltasigma is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# LICENSE file for the licensing terms.

"""This module provides the ds_hann() function, used to generate a Hann 
window that does not smear tones located exactly in a bin.

import numpy as np

[docs]def ds_hann(n): """A Hann window of length :math:`n`. The Hann window, aka *the raised cosine window*, is defined as: .. math:: w(x) = 0.5\\ \\left(1 - cos\\left(\\frac{2 \\pi x}{n}\\right) \\right) This windowing function does not smear tones located exactly in a bin. **Parameters:** n : integer The window length, in number of samples. **Returns:** w : 1d nd_array The Hann window. .. note:: Functionally equivalent to numpy's ``hanning()``, provided to ease porting of code from MATLAB. Also, we take care always to return an array of dimensions ``(n,)`` and type ``float_``. .. plot:: import pylab as plt from deltasigma import ds_hann x = ds_hann(100) plt.figure(figsize=(12, 5)) plt.plot(x, 'o-') ax = plt.gca() ax.set_ylim(0, 1.02) plt.grid(True) plt.title("100-samples Hann window") plt.xlabel("Sample #") plt.ylabel("Value") """ x = np.arange(n, dtype='float_') return .5*(1 - np.cos(2*np.pi*x/n))