diff options
| author | Ben Reynwar <ben@reynwar.net> | 2013-03-07 23:27:44 -0700 |
|---|---|---|
| committer | Ben Reynwar <ben@reynwar.net> | 2013-03-07 23:27:44 -0700 |
| commit | ae30f247616b6229fb304e30fecf3f82ae09dbf6 (patch) | |
| tree | 74c1d6cd8300b44b6280c56bc4ad257c40390b3e /gr-analog/python/fm_emph.py | |
| parent | e8b4e619479dd23d87c3aef042f2452f867a1e18 (diff) | |
analog: Enabling uninstalled python imports.
Diffstat (limited to 'gr-analog/python/fm_emph.py')
| -rw-r--r-- | gr-analog/python/fm_emph.py | 150 |
1 files changed, 0 insertions, 150 deletions
diff --git a/gr-analog/python/fm_emph.py b/gr-analog/python/fm_emph.py deleted file mode 100644 index 2821f6e3cd..0000000000 --- a/gr-analog/python/fm_emph.py +++ /dev/null @@ -1,150 +0,0 @@ -# -# Copyright 2005,2007,2012 Free Software Foundation, Inc. -# -# This file is part of GNU Radio -# -# GNU Radio is free software; you can redistribute it and/or modify -# it under the terms of the GNU General Public License as published by -# the Free Software Foundation; either version 3, or (at your option) -# any later version. -# -# GNU Radio 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 -# GNU General Public License for more details. -# -# You should have received a copy of the GNU General Public License -# along with GNU Radio; see the file COPYING. If not, write to -# the Free Software Foundation, Inc., 51 Franklin Street, -# Boston, MA 02110-1301, USA. -# - -from gnuradio import gr, filter -import math - -# -# 1 -# H(s) = ------- -# 1 + s -# -# tau is the RC time constant. -# critical frequency: w_p = 1/tau -# -# We prewarp and use the bilinear z-transform to get our IIR coefficients. -# See "Digital Signal Processing: A Practical Approach" by Ifeachor and Jervis -# - -class fm_deemph(gr.hier_block2): - """ - FM Deemphasis IIR filter. - """ - - - def __init__(self, fs, tau=75e-6): - """ - - Args: - fs: sampling frequency in Hz (float) - tau: Time constant in seconds (75us in US, 50us in EUR) (float) - """ - gr.hier_block2.__init__(self, "fm_deemph", - gr.io_signature(1, 1, gr.sizeof_float), # Input signature - gr.io_signature(1, 1, gr.sizeof_float)) # Output signature - - w_p = 1/tau - w_pp = math.tan(w_p / (fs * 2)) # prewarped analog freq - - a1 = (w_pp - 1)/(w_pp + 1) - b0 = w_pp/(1 + w_pp) - b1 = b0 - - btaps = [b0, b1] - ataps = [1, a1] - - if 0: - print "btaps =", btaps - print "ataps =", ataps - global plot1 - plot1 = gru.gnuplot_freqz(gru.freqz(btaps, ataps), fs, True) - - deemph = filter.iir_filter_ffd(btaps, ataps) - self.connect(self, deemph, self) - -# -# 1 + s*t1 -# H(s) = ---------- -# 1 + s*t2 -# -# I think this is the right transfer function. -# -# -# This fine ASCII rendition is based on Figure 5-15 -# in "Digital and Analog Communication Systems", Leon W. Couch II -# -# -# R1 -# +-----||------+ -# | | -# o------+ +-----+--------o -# | C1 | | -# +----/\/\/\/--+ \ -# / -# \ R2 -# / -# \ -# | -# o--------------------------+--------o -# -# f1 = 1/(2*pi*t1) = 1/(2*pi*R1*C) -# -# 1 R1 + R2 -# f2 = ------- = ------------ -# 2*pi*t2 2*pi*R1*R2*C -# -# t1 is 75us in US, 50us in EUR -# f2 should be higher than our audio bandwidth. -# -# -# The Bode plot looks like this: -# -# -# /---------------- -# / -# / <-- slope = 20dB/decade -# / -# -------------/ -# f1 f2 -# -# We prewarp and use the bilinear z-transform to get our IIR coefficients. -# See "Digital Signal Processing: A Practical Approach" by Ifeachor and Jervis -# - -class fm_preemph(gr.hier_block2): - """ - FM Preemphasis IIR filter. - """ - def __init__(self, fs, tau=75e-6): - """ - - Args: - fs: sampling frequency in Hz (float) - tau: Time constant in seconds (75us in US, 50us in EUR) (float) - """ - - gr.hier_block2.__init__(self, "fm_deemph", - gr.io_signature(1, 1, gr.sizeof_float), # Input signature - gr.io_signature(1, 1, gr.sizeof_float)) # Output signature - - # FIXME make this compute the right answer - - btaps = [1] - ataps = [1] - - if 0: - print "btaps =", btaps - print "ataps =", ataps - global plot2 - plot2 = gru.gnuplot_freqz(gru.freqz(btaps, ataps), fs, True) - - preemph = filter.iir_filter_ffd(btaps, ataps) - self.connect(self, preemph, self) |