resampler.py

#!/usr/bin/env python
#
# Copyright 2009,2012,2013 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
#

from gnuradio import gr
from gnuradio import filter
from gnuradio import blocks
import sys
import numpy

try:
    from gnuradio import analog
except ImportError:
    sys.stderr.write("Error: Program requires gr-analog.\n")
    sys.exit(1)

try:
    from matplotlib import pyplot
except ImportError:
    sys.stderr.write(
        "Error: Program requires matplotlib (see: matplotlib.sourceforge.net).\n")
    sys.exit(1)


class mytb(gr.top_block):
    def __init__(self, fs_in, fs_out, fc, N=10000):
        gr.top_block.__init__(self)

        rerate = float(fs_out) / float(fs_in)
        print("Resampling from %f to %f by %f " % (fs_in, fs_out, rerate))

        # Creating our own taps
        taps = filter.firdes.low_pass_2(32, 32, 0.25, 0.1, 80)

        self.src = analog.sig_source_c(fs_in, analog.GR_SIN_WAVE, fc, 1)
        #self.src = analog.noise_source_c(analog.GR_GAUSSIAN, 1)
        self.head = blocks.head(gr.sizeof_gr_complex, N)

        # A resampler with our taps
        self.resamp_0 = filter.pfb.arb_resampler_ccf(rerate, taps,
                                                     flt_size=32)

        # A resampler that just needs a resampling rate.
        # Filter is created for us and designed to cover
        # entire bandwidth of the input signal.
        # An optional atten=XX rate can be used here to
        # specify the out-of-band rejection (default=80).
        self.resamp_1 = filter.pfb.arb_resampler_ccf(rerate)

        self.snk_in = blocks.vector_sink_c()
        self.snk_0 = blocks.vector_sink_c()
        self.snk_1 = blocks.vector_sink_c()

        self.connect(self.src, self.head, self.snk_in)
        self.connect(self.head, self.resamp_0, self.snk_0)
        self.connect(self.head, self.resamp_1, self.snk_1)


def main():
    fs_in = 8000
    fs_out = 20000
    fc = 1000
    N = 10000

    tb = mytb(fs_in, fs_out, fc, N)
    tb.run()

    # Plot PSD of signals
    nfftsize = 2048
    fig1 = pyplot.figure(1, figsize=(10, 10), facecolor="w")
    sp1 = fig1.add_subplot(2, 1, 1)
    sp1.psd(tb.snk_in.data(), NFFT=nfftsize,
            noverlap=nfftsize / 4, Fs=fs_in)
    sp1.set_title(("Input Signal at f_s=%.2f kHz" % (fs_in / 1000.0)))
    sp1.set_xlim([-fs_in / 2, fs_in / 2])

    sp2 = fig1.add_subplot(2, 1, 2)
    sp2.psd(tb.snk_0.data(), NFFT=nfftsize,
            noverlap=nfftsize / 4, Fs=fs_out,
            label="With our filter")
    sp2.psd(tb.snk_1.data(), NFFT=nfftsize,
            noverlap=nfftsize / 4, Fs=fs_out,
            label="With auto-generated filter")
    sp2.set_title(("Output Signals at f_s=%.2f kHz" % (fs_out / 1000.0)))
    sp2.set_xlim([-fs_out / 2, fs_out / 2])
    sp2.legend()

    # Plot signals in time
    Ts_in = 1.0 / fs_in
    Ts_out = 1.0 / fs_out
    t_in = numpy.arange(0, len(tb.snk_in.data()) * Ts_in, Ts_in)
    t_out = numpy.arange(0, len(tb.snk_0.data()) * Ts_out, Ts_out)

    fig2 = pyplot.figure(2, figsize=(10, 10), facecolor="w")
    sp21 = fig2.add_subplot(2, 1, 1)
    sp21.plot(t_in, tb.snk_in.data())
    sp21.set_title(("Input Signal at f_s=%.2f kHz" % (fs_in / 1000.0)))
    sp21.set_xlim([t_in[100], t_in[200]])

    sp22 = fig2.add_subplot(2, 1, 2)
    sp22.plot(t_out, tb.snk_0.data(),
              label="With our filter")
    sp22.plot(t_out, tb.snk_1.data(),
              label="With auto-generated filter")
    sp22.set_title(("Output Signals at f_s=%.2f kHz" % (fs_out / 1000.0)))
    r = float(fs_out) / float(fs_in)
    sp22.set_xlim([t_out[r * 100], t_out[r * 200]])
    sp22.legend()

    pyplot.show()


if __name__ == "__main__":
    main()