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#
# Copyright 2005,2007 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING. If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#
import sys
from gnuradio import gr
from gnuradio import fft
from gnuradio import blocks
def _generate_synthesis_taps(mpoints):
return [] # FIXME
def _split_taps(taps, mpoints):
assert (len(taps) % mpoints) == 0
result = [list() for x in range(mpoints)]
for i in xrange(len(taps)):
(result[i % mpoints]).append(taps[i])
return [tuple(x) for x in result]
class synthesis_filterbank(gr.hier_block2):
"""
Uniformly modulated polyphase DFT filter bank: synthesis
See http://cnx.org/content/m10424/latest
"""
def __init__(self, mpoints, taps=None):
"""
Takes M complex streams in, produces single complex stream out
that runs at M times the input sample rate
Args:
mpoints: number of freq bins/interpolation factor/subbands
taps: filter taps for subband filter
The channel spacing is equal to the input sample rate.
The total bandwidth and output sample rate are equal the input
sample rate * nchannels.
Output stream to frequency mapping:
channel zero is at zero frequency.
if mpoints is odd:
Channels with increasing positive frequencies come from
channels 1 through (N-1)/2.
Channel (N+1)/2 is the maximum negative frequency, and
frequency increases through N-1 which is one channel lower
than the zero frequency.
if mpoints is even:
Channels with increasing positive frequencies come from
channels 1 through (N/2)-1.
Channel (N/2) is evenly split between the max positive and
negative bins.
Channel (N/2)+1 is the maximum negative frequency, and
frequency increases through N-1 which is one channel lower
than the zero frequency.
Channels near the frequency extremes end up getting cut
off by subsequent filters and therefore have diminished
utility.
"""
item_size = gr.sizeof_gr_complex
gr.hier_block2.__init__(self, "synthesis_filterbank",
gr.io_signature(mpoints, mpoints, item_size), # Input signature
gr.io_signature(1, 1, item_size)) # Output signature
if taps is None:
taps = _generate_synthesis_taps(mpoints)
# pad taps to multiple of mpoints
r = len(taps) % mpoints
if r != 0:
taps = taps + (mpoints - r) * (0,)
# split in mpoints separate set of taps
sub_taps = _split_taps(taps, mpoints)
self.ss2v = blocks.streams_to_vector(item_size, mpoints)
self.ifft = fft.fft_vcc(mpoints, False, [])
self.v2ss = blocks.vector_to_streams(item_size, mpoints)
# mpoints filters go in here...
self.ss2s = blocks.streams_to_stream(item_size, mpoints)
for i in range(mpoints):
self.connect((self, i), (self.ss2v, i))
self.connect(self.ss2v, self.ifft, self.v2ss)
# build mpoints fir filters...
for i in range(mpoints):
f = fft.fft_filter_ccc(1, sub_taps[i])
self.connect((self.v2ss, i), f)
self.connect(f, (self.ss2s, i))
self.connect(self.ss2s, self)
class analysis_filterbank(gr.hier_block2):
"""
Uniformly modulated polyphase DFT filter bank: analysis
See http://cnx.org/content/m10424/latest
"""
def __init__(self, mpoints, taps=None):
"""
Takes 1 complex stream in, produces M complex streams out
that runs at 1/M times the input sample rate
Args:
mpoints: number of freq bins/interpolation factor/subbands
taps: filter taps for subband filter
Same channel to frequency mapping as described above.
"""
item_size = gr.sizeof_gr_complex
gr.hier_block2.__init__(self, "analysis_filterbank",
gr.io_signature(1, 1, item_size), # Input signature
gr.io_signature(mpoints, mpoints, item_size)) # Output signature
if taps is None:
taps = _generate_synthesis_taps(mpoints)
# pad taps to multiple of mpoints
r = len(taps) % mpoints
if r != 0:
taps = taps + (mpoints - r) * (0,)
# split in mpoints separate set of taps
sub_taps = _split_taps(taps, mpoints)
# print >> sys.stderr, "mpoints =", mpoints, "len(sub_taps) =", len(sub_taps)
self.s2ss = blocks.stream_to_streams(item_size, mpoints)
# filters here
self.ss2v = blocks.streams_to_vector(item_size, mpoints)
self.fft = fft.fft_vcc(mpoints, True, [])
self.v2ss = blocks.vector_to_streams(item_size, mpoints)
self.connect(self, self.s2ss)
# build mpoints fir filters...
for i in range(mpoints):
f = fft.fft_filter_ccc(1, sub_taps[mpoints-i-1])
self.connect((self.s2ss, i), f)
self.connect(f, (self.ss2v, i))
self.connect((self.v2ss, i), (self, i))
self.connect(self.ss2v, self.fft, self.v2ss)
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