_dbp.py

# -*- coding: utf-8 -*-
# _dbp.py
# This module provides the dbp 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
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# LICENSE file for the licensing terms.

"""This module provides the dbp() function, used to convert a power gain to dB.
"""

import numpy as np

from ._utils import carray, save_input_form, restore_input_form

def dbp(x):
	"""The dB equivalent of the power ratio ``x``.

	.. math::

	    P_{dB} = 10 \\mathrm{log}_{10}(x)

	**Parameters:**

	x : scalar or sequence
	    The power ratio to be converted.

	**Returns:**

	PdB : scalar or sequence
	       The input expressed in dB.

	.. seealso:: :func:`undbp`, :func:`db`, :func:`dbm`, :func:`dbv`

	"""
	iform = save_input_form(x)
	x = carray(x)
	y = -np.Inf*np.ones(x.shape)
	nonzero = (x != 0)
	y[nonzero] = 10.*np.log10(np.abs(x[nonzero]))
	return restore_input_form(y, iform)

def test_dbp():
	"""Test function for dbp()
	"""
	tv = np.array([2])
	r = np.array([3.01029996])
	res = dbp(tv)
	assert np.allclose(r, res, atol=1e-8, rtol=1e-5)
	tv = 2
	r = 3.01029996
	res = dbp(tv)
	assert np.allclose(r, res, atol=1e-8, rtol=1e-5)
	assert np.isscalar(res) # check for type coherence
	tv = 2, 2
	r = 3.01029996, 3.01029996
	res = dbp(tv)
	assert np.allclose(r, res, atol=1e-8, rtol=1e-5)