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 = gr.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 gr.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 = gr.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):
"""
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 = gr.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=0):
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)
taps = gr.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 = gr.remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps
def high_pass (Fs, freq1, freq2, stopband_atten_db, passband_ripple_db,
nextra_taps=0):
"""FIXME: broken"""
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)
taps = gr.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 = gr.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 gr.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 = gr.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 = gr.remez (n + nextra_taps, fo, ao, w, "bandpass")
return taps