# Source code for deltasigma._evalMixedTF

# -*- coding: utf-8 -*-
# _evalMixedTF.py
# Module providing the evalMixedTF 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.
"""Module providing the evalMixedTF() function
"""
from __future__ import division
import numpy as np
from ._evalTFP import evalTFP
from ._utils import carray, restore_input_form, save_input_form
[docs]def evalMixedTF(tf, f, df=1e-5):
"""Compute a mixed transfer function.
Mathematically, it means to evaluate the sum of products:
.. math::
TF(f) = \\sum_i H_{z,i}(f) \\cdot H_{s,i}(f)
**Parameters:**
tf : dict
``tf`` is a dictionary of lists of 1d arrays, with keys 'Hs' and 'Hz',
which represent continuous-time and discrete-time TFs which will be
evaluated, multiplied together and then added up.
f : scalar or sequence-like
The frequencies (or frequency, if ``f`` is a scalar) at which the
product will be evaluated.
df : float, optional
If the method happens to evaluate a transfer function in a root, it
will move away of ``df``, defaulting to 1E-5.
**Returns:**
TF : scalar or sequence
The sum of products computed at ``f``.
"""
iform = save_input_form(f)
f = carray(f)
H = np.zeros(f.shape)
for i in range(max(len(tf['Hs']), len(tf['Hz']))):
H = H + evalTFP(tf['Hs'][i], tf['Hz'][i], f)
err = np.logical_or(np.isnan(H), np.isinf(H))
if np.any(err):
for i in np.where(err):
H[i] = evalMixedTF(tf, f[i] + df, df*10)
return restore_input_form(H, iform)