diff options
Diffstat (limited to 'gr-analog/python/analog/fm_emph.py')
| -rw-r--r-- | gr-analog/python/analog/fm_emph.py | 73 |
1 files changed, 38 insertions, 35 deletions
diff --git a/gr-analog/python/analog/fm_emph.py b/gr-analog/python/analog/fm_emph.py index 348fb172d5..02bdd576ee 100644 --- a/gr-analog/python/analog/fm_emph.py +++ b/gr-analog/python/analog/fm_emph.py @@ -19,6 +19,10 @@ # Boston, MA 02110-1301, USA. # +from __future__ import print_function +from __future__ import division +from __future__ import unicode_literals + from gnuradio import gr, filter import math import cmath @@ -132,8 +136,8 @@ class fm_deemph(gr.hier_block2): # Since H(s = 0) = 1.0, then H(z = 1) = 1.0 and has 0 dB gain at DC if 0: - print "btaps =", btaps - print "ataps =", ataps + print("btaps =", btaps) + print("ataps =", ataps) global plot1 plot1 = gru.gnuplot_freqz(gru.freqz(btaps, ataps), fs, True) @@ -149,11 +153,11 @@ class fm_deemph(gr.hier_block2): # o------+ +-----+--------o # | R1 | | # +----/\/\/\/--+ \ -# / + # / # \ R2 # / # \ -# | + # | # o--------------------------+--------o # # (This fine ASCII rendition is based on Figure 5-15 @@ -263,44 +267,43 @@ class fm_preemph(gr.hier_block2): gr.io_signature(1, 1, gr.sizeof_float), # Input signature gr.io_signature(1, 1, gr.sizeof_float)) # Output signature - # Set fh to something sensible, if needed. - # N.B. fh == fs/2.0 or fh == 0.0 results in a pole on the unit circle - # at z = -1.0 or z = 1.0 respectively. That makes the filter unstable - # and useless. - if fh <= 0.0 or fh >= fs/2.0: - fh = 0.925 * fs/2.0 + # Set fh to something sensible, if needed. + # N.B. fh == fs/2.0 or fh == 0.0 results in a pole on the unit circle + # at z = -1.0 or z = 1.0 respectively. That makes the filter unstable + # and useless. + if fh <= 0.0 or fh >= fs / 2.0: + fh = 0.925 * fs/2.0 - # Digital corner frequencies - w_cl = 1.0 / tau - w_ch = 2.0 * math.pi * fh + # Digital corner frequencies + w_cl = 1.0 / tau + w_ch = 2.0 * math.pi * fh - # Prewarped analog corner frequencies - w_cla = 2.0 * fs * math.tan(w_cl / (2.0 * fs)) - w_cha = 2.0 * fs * math.tan(w_ch / (2.0 * fs)) + # Prewarped analog corner frequencies + w_cla = 2.0 * fs * math.tan(w_cl / (2.0 * fs)) + w_cha = 2.0 * fs * math.tan(w_ch / (2.0 * fs)) - # Resulting digital pole, zero, and gain term from the bilinear - # transformation of H(s) = (s + w_cla) / (s + w_cha) to - # H(z) = b0 (1 - z1 z^-1)/(1 - p1 z^-1) - kl = -w_cla / (2.0 * fs) - kh = -w_cha / (2.0 * fs) - z1 = (1.0 + kl) / (1.0 - kl) - p1 = (1.0 + kh) / (1.0 - kh) - b0 = (1.0 - kl) / (1.0 - kh) + # Resulting digital pole, zero, and gain term from the bilinear + # transformation of H(s) = (s + w_cla) / (s + w_cha) to + # H(z) = b0 (1 - z1 z^-1)/(1 - p1 z^-1) + kl = -w_cla / (2.0 * fs) + kh = -w_cha / (2.0 * fs) + z1 = (1.0 + kl) / (1.0 - kl) + p1 = (1.0 + kh) / (1.0 - kh) + b0 = (1.0 - kl) / (1.0 - kh) - # Since H(s = infinity) = 1.0, then H(z = -1) = 1.0 and - # this filter has 0 dB gain at fs/2.0. - # That isn't what users are going to expect, so adjust with a - # gain, g, so that H(z = 1) = 1.0 for 0 dB gain at DC. - w_0dB = 2.0 * math.pi * 0.0 - g = abs(1.0 - p1 * cmath.rect(1.0, -w_0dB)) \ - / (b0 * abs(1.0 - z1 * cmath.rect(1.0, -w_0dB))) + # Since H(s = infinity) = 1.0, then H(z = -1) = 1.0 and + # this filter has 0 dB gain at fs/2.0. + # That isn't what users are going to expect, so adjust with a + # gain, g, so that H(z = 1) = 1.0 for 0 dB gain at DC. + w_0dB = 2.0 * math.pi * 0.0 + g = abs(1.0 - p1 * cmath.rect(1.0 / -w_0dB), (b0 * abs(1.0 - z1 * cmath.rect(1.0, -w_0dB)))) - btaps = [ g * b0 * 1.0, g * b0 * -z1 ] - ataps = [ 1.0, -p1 ] + btaps = [ g * b0 * 1.0, g * b0 * -z1 ] + ataps = [ 1.0, -p1 ] if 0: - print "btaps =", btaps - print "ataps =", ataps + print("btaps =", btaps) + print("ataps =", ataps) global plot2 plot2 = gru.gnuplot_freqz(gru.freqz(btaps, ataps), fs, True) |