differential QPSK modulation and demodulation.

"""

from math import pi, sqrt

import psk

import cmath

_def_log = False

_def_freq_alpha = 0.010

_def_timing_alpha = 0.100

_def_timing_beta = 0.010

_def_timing_max_dev = 1.5

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

                                                            ('self',), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

                 samples_per_symbol=_def_samples_per_symbol,

                 excess_bw=_def_excess_bw,

                 freq_alpha=_def_freq_alpha,

                 timing_alpha=_def_timing_alpha,

                 timing_max_dev=_def_timing_max_dev,

                 gray_code=_def_gray_code,

	@type excess_bw: float

        @param freq_alpha: loop filter gain for frequency recovery

        @type freq_alpha: float

        @param timing_alpha: timing loop alpha gain

        @type timing_alpha: float

        @param timing_max: timing loop maximum rate deviations

        self._excess_bw = excess_bw

        self._freq_alpha = freq_alpha

        self._freq_beta = 0.25*self._freq_alpha**2

        self._timing_alpha = timing_alpha

        self._timing_beta = _def_timing_beta

        self._timing_max_dev=timing_max_dev

        # Perform phase / fine frequency correction

        # Allow a frequency swing of +/- half of the sample rate

        fmin = -0.5

        fmax = 0.5

                                             fmax, fmin, arity)

        print "Gray code:           %s"   % self._gray_code

        print "RRC roll-off factor: %.2f" % self._excess_bw

        print "FLL gain:            %.2f" % self._freq_alpha

        print "Timing alpha gain:   %.2f" % self._timing_alpha

        print "Timing beta gain:    %.2f" % self._timing_beta

        print "Timing max dev:      %.2f" % self._timing_max_dev

    def _setup_logging(self):

        print "Modulation logging turned on."

    def add_options(parser):

        """

        """

        parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,

                          help="set RRC excess bandwith factor [default=%default] (PSK)")

                          help="disable gray coding on modulated bits (PSK)")

        parser.add_option("", "--freq-alpha", type="float", default=_def_freq_alpha,

                          help="set frequency lock loop alpha gain value [default=%default] (PSK)")

                          help="set timing symbol sync loop gain alpha value [default=%default] (GMSK/PSK)")

                          help="set timing symbol sync loop gain beta value [default=%default] (GMSK/PSK)")

        parser.add_option("", "--timing-max-dev", type="float", default=_def_timing_max_dev,

                          help="set timing symbol sync loop maximum deviation [default=%default] (GMSK/PSK)")

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

            dqpsk2_demod.__init__, ('self',), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

#

# Add these to the mod/demod registry

#