"""
differential BPSK modulation and demodulation.
"""
from gnuradio import gr, gru, modulation_utils, howto
from math import pi, sqrt
import psk
import cmath
from pprint import pprint
# default values (used in __init__ and add_options)
_def_samples_per_symbol = 2
_def_excess_bw = 0.35
_def_gray_code = True
_def_verbose = False
_def_log = False
_def_costas_alpha = 0.1
_def_gain_mu = None
_def_mu = 0.5
_def_omega_relative_limit = 0.005
# /////////////////////////////////////////////////////////////////////////////
# DBPSK modulator
# /////////////////////////////////////////////////////////////////////////////
class dbpsk_mod(gr.hier_block2):
def __init__(self,
samples_per_symbol=_def_samples_per_symbol,
excess_bw=_def_excess_bw,
gray_code=_def_gray_code,
verbose=_def_verbose,
log=_def_log):
gr.hier_block2.__init__(self, "dbpsk_mod",
gr.io_signature(1, 1, gr.sizeof_char), # Input signature
gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
"""
Hierarchical block for RRC-filtered differential BPSK modulation.
The input is a byte stream (unsigned char) and the
output is the complex modulated signal at baseband.
@param samples_per_symbol: samples per baud >= 2
@type samples_per_symbol: integer
@param excess_bw: Root-raised cosine filter excess bandwidth
@type excess_bw: float
@param gray_code: Tell modulator to Gray code the bits
@type gray_code: bool
@param verbose: Print information about modulator?
@type verbose: bool
@param log: Log modulation data to files?
@type log: bool
"""
self._samples_per_symbol = samples_per_symbol
self._excess_bw = excess_bw
self._gray_code = gray_code
if not isinstance(self._samples_per_symbol, int) or self._samples_per_symbol < 2:
raise TypeError, ("sbp must be an integer >= 2, is %d" % self._samples_per_symbol)
arity = pow(2,self.bits_per_symbol())
# turn bytes into k-bit vectors
self.bytes2chunks = \
gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
if self._gray_code:
self.symbol_mapper = gr.map_bb(psk.binary_to_gray[arity])
else:
self.symbol_mapper = gr.map_bb(psk.binary_to_ungray[arity])
self.diffenc = gr.diff_encoder_bb(arity)
self.chunks2symbols = gr.chunks_to_symbols_bc(psk.constellation[arity])
#scrambler
srm_interpolation = 15 #duration of 1 cycle
srm_mask = 0 #should be zero to generate the maximum length sequence
srm_seed = 2
srm_degree = 4 #2^4 + 2^3 + 2^0 = 25 ,ntaps = 15
self.scrambler = howto.interp_gscrambler_cc(srm_interpolation,\
srm_degree,\
srm_mask,\
srm_seed)
# pulse shaping filter
ntaps = 11 * self._samples_per_symbol
self.rrc_taps = gr.firdes.root_raised_cosine(
self._samples_per_symbol, # gain (samples_per_symbol since we're
# interpolating by samples_per_symbol)
self._samples_per_symbol, # sampling rate
1.0, # symbol rate
self._excess_bw, # excess bandwidth (roll-off factor)
ntaps)
self.rrc_filter = gr.interp_fir_filter_ccf(self._samples_per_symbol,
self.rrc_taps)
# Connect
self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
self.chunks2symbols, self.scrambler, self.rrc_filter, self)
if verbose:
self._print_verbage()
if log:
self._setup_logging()
def samples_per_symbol(self):
return self._samples_per_symbol
def bits_per_symbol(self=None): # static method that's also callable on an instance
return 1
bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method. RTFM
def add_options(parser):
"""
Adds DBPSK modulation-specific options to the standard parser
"""
parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
help="set RRC excess bandwith factor [default=%default]")
parser.add_option("", "--no-gray-code", dest="gray_code",
action="store_false", default=True,
help="disable gray coding on modulated bits (PSK)")
add_options=staticmethod(add_options)
def extract_kwargs_from_options(options):
"""
Given command line options, create dictionary suitable for passing to __init__
"""
return modulation_utils.extract_kwargs_from_options(dbpsk_mod.__init__,
('self',), options)
extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
def _print_verbage(self):
print "\nModulator:"
print "bits per symbol: %d" % self.bits_per_symbol()
print "Gray code: %s" % self._gray_code
print "RRC roll-off factor: %.2f" % self._excess_bw
def _setup_logging(self):
print "Modulation logging turned on."
self.connect(self.bytes2chunks,
gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
self.connect(self.symbol_mapper,
gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
self.connect(self.diffenc,
gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
self.connect(self.chunks2symbols,
gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
self.connect(self.rrc_filter,
gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
# /////////////////////////////////////////////////////////////////////////////
# DBPSK demodulator
#
# Differentially coherent detection of differentially encoded BPSK
# /////////////////////////////////////////////////////////////////////////////
class dbpsk_demod(gr.hier_block2):
def __init__(self,
samples_per_symbol=_def_samples_per_symbol,
excess_bw=_def_excess_bw,
costas_alpha=_def_costas_alpha,
gain_mu=_def_gain_mu,
mu=_def_mu,
omega_relative_limit=_def_omega_relative_limit,
gray_code=_def_gray_code,
verbose=_def_verbose,
log=_def_log):
gr.hier_block2.__init__(self, "dbpsk_demod",
gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
gr.io_signature(1, 1, gr.sizeof_char)) # Output signature
"""
Hierarchical block for RRC-filtered differential BPSK demodulation
The input is the complex modulated signal at baseband.
The output is a stream of bits packed 1 bit per byte (LSB)
@param samples_per_symbol: samples per symbol >= 2
@type samples_per_symbol: float
@param excess_bw: Root-raised cosine filter excess bandwidth
@type excess_bw: float
@param costas_alpha: loop filter gain
@type costas_alphas: float
@param gain_mu: for M&M block
@type gain_mu: float
@param mu: for M&M block
@type mu: float
@param omega_relative_limit: for M&M block
@type omega_relative_limit: float
@param gray_code: Tell modulator to Gray code the bits
@type gray_code: bool
@param verbose: Print information about modulator?
@type verbose: bool
@param debug: Print modualtion data to files?
@type debug: bool
"""
self._samples_per_symbol = samples_per_symbol
self._excess_bw = excess_bw
self._costas_alpha = costas_alpha
self._mm_gain_mu = gain_mu
self._mm_mu = mu
self._mm_omega_relative_limit = omega_relative_limit
self._gray_code = gray_code
if samples_per_symbol < 2:
raise TypeError, "samples_per_symbol must be >= 2, is %r" % (samples_per_symbol,)
arity = pow(2,self.bits_per_symbol())
# Automatic gain control
scale = (1.0/16384.0)
self.pre_scaler = gr.multiply_const_cc(scale) # scale the signal from full-range to +-1
#self.agc = gr.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
self.agc = gr.feedforward_agc_cc(16, 2.0)
# RRC data filter
ntaps = 11 * samples_per_symbol
self.rrc_taps = gr.firdes.root_raised_cosine(
1.0, # gain
self._samples_per_symbol, # sampling rate
1.0, # symbol rate
self._excess_bw, # excess bandwidth (roll-off factor)
ntaps)
self.rrc_filter=gr.interp_fir_filter_ccf(1, self.rrc_taps)
# symbol clock recovery
if not self._mm_gain_mu:
self._mm_gain_mu = 0.1
self._mm_omega = self._samples_per_symbol
self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
self._costas_beta = 0.25 * self._costas_alpha * self._costas_alpha
fmin = -0.1
fmax = 0.1
#set descrambler
dsrm_mask = 0 #should be zero to generate the maximum length sequence
dsrm_seed = 2
dsrm_degree = 4 #2^4 + 2^3 + 2^0 = 25 ,ntaps = 15
self.descrambler = howto.decim_gdescrambler_cc(dsrm_degree, dsrm_mask, dsrm_seed)
self.receiver=gr.mpsk_receiver_cc(arity, 0,
self._costas_alpha, self._costas_beta,
fmin, fmax,
self._mm_mu, self._mm_gain_mu,
self._mm_omega, self._mm_gain_omega,
self._mm_omega_relative_limit)
# Do differential decoding based on phase change of symbols
self.diffdec = gr.diff_phasor_cc()
# find closest constellation point
rot = 1
rotated_const = map(lambda pt: pt * rot, psk.constellation[arity])
self.slicer = gr.constellation_decoder_cb(rotated_const, range(arity))
if self._gray_code:
self.symbol_mapper = gr.map_bb(psk.gray_to_binary[arity])
else:
self.symbol_mapper = gr.map_bb(psk.ungray_to_binary[arity])
# unpack the k bit vector into a stream of bits
self.unpack = gr.unpack_k_bits_bb(self.bits_per_symbol())
if verbose:
self._print_verbage()
if log:
self._setup_logging()
# Connect and Initialize base class
self.connect(self, self.pre_scaler, self.agc, self.rrc_filter, self.descrambler, self.receiver,
self.diffdec, self.slicer, self.symbol_mapper, self.unpack, self)
def samples_per_symbol(self):
return self._samples_per_symbol
def bits_per_symbol(self=None): # staticmethod that's also callable on an instance
return 1
bits_per_symbol = staticmethod(bits_per_symbol) # make it a static method. RTFM
def _print_verbage(self):
print "\nDemodulator:"
print "bits per symbol: %d" % self.bits_per_symbol()
print "Gray code: %s" % self._gray_code
print "RRC roll-off factor: %.2f" % self._excess_bw
print "Costas Loop alpha: %.2e" % self._costas_alpha
print "Costas Loop beta: %.2e" % self._costas_beta
print "M&M mu: %.2f" % self._mm_mu
print "M&M mu gain: %.2e" % self._mm_gain_mu
print "M&M omega: %.2f" % self._mm_omega
print "M&M omega gain: %.2e" % self._mm_gain_omega
print "M&M omega limit: %.2f" % self._mm_omega_relative_limit
def _setup_logging(self):
print "Modulation logging turned on."
self.connect(self.pre_scaler,
gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
self.connect(self.agc,
gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
self.connect(self.rrc_filter,
gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
self.connect(self.receiver,
gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
self.connect(self.diffdec,
gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
self.connect(self.slicer,
gr.file_sink(gr.sizeof_char, "rx_slicer.dat"))
self.connect(self.symbol_mapper,
gr.file_sink(gr.sizeof_char, "rx_symbol_mapper.dat"))
self.connect(self.unpack,
gr.file_sink(gr.sizeof_char, "rx_unpack.dat"))
def add_options(parser):
"""
Adds DBPSK demodulation-specific options to the standard parser
"""
parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
help="set RRC excess bandwith factor [default=%default] (PSK)")
parser.add_option("", "--no-gray-code", dest="gray_code",
action="store_false", default=_def_gray_code,
help="disable gray coding on modulated bits (PSK)")
parser.add_option("", "--costas-alpha", type="float", default=None,
help="set Costas loop alpha value [default=%default] (PSK)")
parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
help="set M&M symbol sync loop gain mu value [default=%default] (GMSK/PSK)")
parser.add_option("", "--mu", type="float", default=_def_mu,
help="set M&M symbol sync loop mu value [default=%default] (GMSK/PSK)")
parser.add_option("", "--omega-relative-limit", type="float", default=_def_omega_relative_limit,
help="M&M clock recovery omega relative limit [default=%default] (GMSK/PSK)")
add_options=staticmethod(add_options)
def extract_kwargs_from_options(options):
"""
Given command line options, create dictionary suitable for passing to __init__
"""
return modulation_utils.extract_kwargs_from_options(
dbpsk_demod.__init__, ('self',), options)
extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)
#
# Add these to the mod/demod registry
#
modulation_utils.add_type_1_mod('dbpsk', dbpsk_mod)
modulation_utils.add_type_1_demod('dbpsk', dbpsk_demod)
最終更新：2011年06月29日 02:24
