diff options
| author | trondeau <trondeau@221aa14e-8319-0410-a670-987f0aec2ac5> | 2009-08-05 01:36:09 +0000 |
|---|---|---|
| committer | trondeau <trondeau@221aa14e-8319-0410-a670-987f0aec2ac5> | 2009-08-05 01:36:09 +0000 |
| commit | e0003f3fc2b49d52a647281af3695b386ec7d8bf (patch) | |
| tree | 952a4e241b9f7b487ea9ad7a3e12655a81b6430f /gnuradio-core/src/python/gnuradio/optfir.py | |
| parent | f6a400a8192ebee931ee45d712ffa889ba321234 (diff) | |
Fixed optfir for producing equiripple FIR filters. Does LPF, fixes the HPF, and adds BPF (real).
git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@11537 221aa14e-8319-0410-a670-987f0aec2ac5
Diffstat (limited to 'gnuradio-core/src/python/gnuradio/optfir.py')
| -rw-r--r-- | gnuradio-core/src/python/gnuradio/optfir.py | 55 |
1 files changed, 49 insertions, 6 deletions
diff --git a/gnuradio-core/src/python/gnuradio/optfir.py b/gnuradio-core/src/python/gnuradio/optfir.py index bd43fcc974..06a0eea614 100644 --- a/gnuradio-core/src/python/gnuradio/optfir.py +++ b/gnuradio-core/src/python/gnuradio/optfir.py @@ -1,5 +1,5 @@ # -# Copyright 2004,2005 Free Software Foundation, Inc. +# Copyright 2004,2005,2009 Free Software Foundation, Inc. # # This file is part of GNU Radio # @@ -34,25 +34,68 @@ remez = gr.remez # ---------------------------------------------------------------- +## Builds a low pass filter. +# @param gain Filter gain in the passband (linear) +# @param Fs Sampling rate (sps) +# @param freq1 End of pass band (in Hz) +# @param freq2 Start of stop band (in Hz) +# @param passband_ripple_db Pass band ripple in dB (should be small, < 1) +# @param stopband_atten_db Stop band attenuation in dB (should be large, >= 60) +# @param nextra_taps Extra taps to use in the filter (default=2) def low_pass (gain, Fs, freq1, freq2, passband_ripple_db, stopband_atten_db, - nextra_taps=0): + 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 -# FIXME high_passs is broken... -def high_pass (Fs, freq1, freq2, stopband_atten_db, passband_ripple_db, - nextra_taps=0): - """FIXME: broken""" +## Builds a band pass filter. +# @param gain Filter gain in the passband (linear) +# @param Fs Sampling rate (sps) +# @param freq1 End of stop band (in Hz) +# @param freq2 Start of pass band (in Hz) +# @param passband_ripple_db Pass band ripple in dB (should be small, < 1) +# @param stopband_atten_db Stop band attenuation in dB (should be large, >= 60) +# @param nextra_taps Extra taps to use in the filter (default=2) +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 + +## Builds a high pass filter. +# @param gain Filter gain in the passband (linear) +# @param Fs Sampling rate (sps) +# @param freq1 End of stop band (in Hz) +# @param freq2 Start of pass band (in Hz) +# @param passband_ripple_db Pass band ripple in dB (should be small, < 1) +# @param stopband_atten_db Stop band attenuation in dB (should be large, >= 60) +# @param nextra_taps Extra taps to use in the filter (default=2) +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 |