def high_pass(gain,
Fs,
freq1,
freq2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
"""
Builds a high pass filter.
Args:
gain: Filter gain in the passband (linear)
Fs: Sampling rate (sps)
freq1: End of stop band (in Hz)
freq2: Start of pass band (in Hz)
passband_ripple_db: Pass band ripple in dB (should be small, < 1)
stopband_atten_db: Stop band attenuation in dB (should be large, >= 60)
nextra_taps: Extra taps to use in the filter (default=2)
"""
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (0, 1)
(n, fo, ao, w) = remezord([freq1, freq2], desired_ampls,
[stopband_dev, passband_dev], Fs)
# For a HPF, we need to use an odd number of taps
# In filter.remez, ntaps = n+1, so n must be even
if ((n + nextra_taps) % 2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_pass(gain,
Fs,
freq_sb1,
freq_pb1,
freq_pb2,
freq_sb2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
"""
Builds a band pass filter.
Args:
gain: Filter gain in the passband (linear)
Fs: Sampling rate (sps)
freq_sb1: End of stop band (in Hz)
freq_pb1: Start of pass band (in Hz)
freq_pb2: End of pass band (in Hz)
freq_sb2: Start of stop band (in Hz)
passband_ripple_db: Pass band ripple in dB (should be small, < 1)
stopband_atten_db: Stop band attenuation in dB (should be large, >= 60)
nextra_taps: Extra taps to use in the filter (default=2)
"""
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (0, gain, 0)
desired_freqs = [freq_sb1, freq_pb1, freq_pb2, freq_sb2]
desired_ripple = [stopband_dev, passband_dev, stopband_dev]
(n, fo, ao, w) = remezord(desired_freqs, desired_ampls, desired_ripple, Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def high_pass (gain, Fs, freq1, freq2, passband_ripple_db, stopband_atten_db,
nextra_taps=2):
"""
Builds a high pass filter.
Args:
gain: Filter gain in the passband (linear)
Fs: Sampling rate (sps)
freq1: End of stop band (in Hz)
freq2: Start of pass band (in Hz)
passband_ripple_db: Pass band ripple in dB (should be small, < 1)
stopband_atten_db: Stop band attenuation in dB (should be large, >= 60)
nextra_taps: Extra taps to use in the filter (default=2)
"""
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (0, 1)
(n, fo, ao, w) = remezord ([freq1, freq2], desired_ampls,
[stopband_dev, passband_dev], Fs)
# For a HPF, we need to use an odd number of taps
# In filter.remez, ntaps = n+1, so n must be even
if((n+nextra_taps)%2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_pass (gain, Fs, freq_sb1, freq_pb1, freq_pb2, freq_sb2,
passband_ripple_db, stopband_atten_db,
nextra_taps=2):
"""
Builds a band pass filter.
Args:
gain: Filter gain in the passband (linear)
Fs: Sampling rate (sps)
freq_sb1: End of stop band (in Hz)
freq_pb1: Start of pass band (in Hz)
freq_pb2: End of pass band (in Hz)
freq_sb2: Start of stop band (in Hz)
passband_ripple_db: Pass band ripple in dB (should be small, < 1)
stopband_atten_db: Stop band attenuation in dB (should be large, >= 60)
nextra_taps: Extra taps to use in the filter (default=2)
"""
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (0, gain, 0)
desired_freqs = [freq_sb1, freq_pb1, freq_pb2, freq_sb2]
desired_ripple = [stopband_dev, passband_dev, stopband_dev]
(n, fo, ao, w) = remezord (desired_freqs, desired_ampls,
desired_ripple, Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def test_low_pass(self):
gain = 1
Fs = 1
freq1 = 0.1
freq2 = 0.2
passband_ripple_db = 0.01
stopband_atten_db = 60
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (gain, 0)
(n, fo, ao, w) = remezord([freq1, freq2], desired_ampls,
[passband_dev, stopband_dev], Fs)
new_taps = filter.pm_remez(n + 2, fo, ao, w, "bandpass")
known_taps = (
-0.0008370135734511828, -0.0006622211673134374,
0.0008501079576365787, 0.003059609130249229, 0.003202235537205373,
-0.001000899296974219, -0.007589728680590891,
-0.009790921118281865, -0.001524210202628562, 0.014373535837200111,
0.02392881326993834, 0.011798133085019008, -0.021954446348997188,
-0.05293436740264934, -0.04375787096766848, 0.028038890498420392,
0.14612655590172896, 0.25738578419108626, 0.302967004188747,
0.25738578419108626, 0.14612655590172896, 0.028038890498420392,
-0.04375787096766848, -0.05293436740264934, -0.021954446348997188,
0.011798133085019008, 0.02392881326993834, 0.014373535837200111,
-0.001524210202628562, -0.009790921118281865,
-0.007589728680590891, -0.001000899296974219, 0.003202235537205373,
0.003059609130249229, 0.0008501079576365787,
-0.0006622211673134374, -0.0008370135734511828)
self.assertFloatTuplesAlmostEqual(known_taps, new_taps, 5)
def band_reject (gain, Fs, freq_pb1, freq_sb1, freq_sb2, freq_pb2,
passband_ripple_db, stopband_atten_db,
nextra_taps=2):
"""
Builds a band reject filter
spinning it up to the right center frequency
Args:
gain: Filter gain in the passband (linear)
Fs: Sampling rate (sps)
freq_pb1: End of pass band (in Hz)
freq_sb1: Start of stop band (in Hz)
freq_sb2: End of stop band (in Hz)
freq_pb2: Start of pass band (in Hz)
passband_ripple_db: Pass band ripple in dB (should be small, < 1)
stopband_atten_db: Stop band attenuation in dB (should be large, >= 60)
nextra_taps: Extra taps to use in the filter (default=2)
"""
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (gain, 0, gain)
desired_freqs = [freq_pb1, freq_sb1, freq_sb2, freq_pb2]
desired_ripple = [passband_dev, stopband_dev, passband_dev]
(n, fo, ao, w) = remezord (desired_freqs, desired_ampls,
desired_ripple, Fs)
# Make sure we use an odd number of taps
if((n+nextra_taps)%2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def low_pass (gain, Fs, freq1, freq2, passband_ripple_db, stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (gain, 0)
(n, fo, ao, w) = remezord ([freq1, freq2], desired_ampls,
[passband_dev, stopband_dev], Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_pass (gain, Fs, freq_sb1, freq_pb1, freq_pb2, freq_sb2,
passband_ripple_db, stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (0, gain, 0)
desired_freqs = [freq_sb1, freq_pb1, freq_pb2, freq_sb2]
desired_ripple = [stopband_dev, passband_dev, stopband_dev]
(n, fo, ao, w) = remezord (desired_freqs, desired_ampls,
desired_ripple, Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def high_pass (gain, Fs, freq1, freq2, passband_ripple_db, stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (0, 1)
(n, fo, ao, w) = remezord ([freq1, freq2], desired_ampls,
[stopband_dev, passband_dev], Fs)
# For a HPF, we need to use an odd number of taps
# In filter.remez, ntaps = n+1, so n must be even
if((n+nextra_taps)%2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def low_pass(gain,
Fs,
freq1,
freq2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (gain, 0)
(n, fo, ao, w) = remezord([freq1, freq2], desired_ampls,
[passband_dev, stopband_dev], Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_reject (gain, Fs, freq_pb1, freq_sb1, freq_sb2, freq_pb2,
passband_ripple_db, stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev (passband_ripple_db)
stopband_dev = stopband_atten_to_dev (stopband_atten_db)
desired_ampls = (gain, 0, gain)
desired_freqs = [freq_pb1, freq_sb1, freq_sb2, freq_pb2]
desired_ripple = [passband_dev, stopband_dev, passband_dev]
(n, fo, ao, w) = remezord (desired_freqs, desired_ampls,
desired_ripple, Fs)
# Make sure we use an odd number of taps
if((n+nextra_taps)%2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_pass(gain,
Fs,
freq_sb1,
freq_pb1,
freq_pb2,
freq_sb2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (0, gain, 0)
desired_freqs = [freq_sb1, freq_pb1, freq_pb2, freq_sb2]
desired_ripple = [stopband_dev, passband_dev, stopband_dev]
(n, fo, ao, w) = remezord(desired_freqs, desired_ampls, desired_ripple, Fs)
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def high_pass(gain,
Fs,
freq1,
freq2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (0, 1)
(n, fo, ao, w) = remezord([freq1, freq2], desired_ampls,
[stopband_dev, passband_dev], Fs)
# For a HPF, we need to use an odd number of taps
# In filter.remez, ntaps = n+1, so n must be even
if ((n + nextra_taps) % 2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def band_reject(gain,
Fs,
freq_pb1,
freq_sb1,
freq_sb2,
freq_pb2,
passband_ripple_db,
stopband_atten_db,
nextra_taps=2):
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (gain, 0, gain)
desired_freqs = [freq_pb1, freq_sb1, freq_sb2, freq_pb2]
desired_ripple = [passband_dev, stopband_dev, passband_dev]
(n, fo, ao, w) = remezord(desired_freqs, desired_ampls, desired_ripple, Fs)
# Make sure we use an odd number of taps
if ((n + nextra_taps) % 2 == 1):
n += 1
# The remezord typically under-estimates the filter order, so add 2 taps by default
taps = filter.pm_remez(n + nextra_taps, fo, ao, w, "bandpass")
return taps
def test_low_pass(self):
gain = 1
Fs = 1
freq1 = 0.1
freq2 = 0.2
passband_ripple_db = 0.01
stopband_atten_db = 60
passband_dev = passband_ripple_to_dev(passband_ripple_db)
stopband_dev = stopband_atten_to_dev(stopband_atten_db)
desired_ampls = (gain, 0)
(n, fo, ao, w) = remezord([freq1, freq2], desired_ampls,
[passband_dev, stopband_dev], Fs)
new_taps = filter.pm_remez(n + 2, fo, ao, w, "bandpass")
known_taps = (-0.0008370135734511828, -0.0006622211673134374,
0.0008501079576365787, 0.003059609130249229,
0.003202235537205373, -0.001000899296974219,
-0.007589728680590891, -0.009790921118281865,
-0.001524210202628562, 0.014373535837200111,
0.02392881326993834, 0.011798133085019008,
-0.021954446348997188, -0.05293436740264934,
-0.04375787096766848, 0.028038890498420392,
0.14612655590172896, 0.25738578419108626,
0.302967004188747, 0.25738578419108626,
0.14612655590172896, 0.028038890498420392,
-0.04375787096766848, -0.05293436740264934,
-0.021954446348997188, 0.011798133085019008,
0.02392881326993834, 0.014373535837200111,
-0.001524210202628562, -0.009790921118281865,
-0.007589728680590891, -0.001000899296974219,
0.003202235537205373, 0.003059609130249229,
0.0008501079576365787, -0.0006622211673134374,
-0.0008370135734511828)
self.assertFloatTuplesAlmostEqual(known_taps, new_taps, 5)
