Source code for deltasigma._evalMixedTF

# -*- coding: utf-8 -*-
# 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
# 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)