def demodulate(self, samples):
if self.demodtype == "envelop":
return self.avgfilter(numpy.abs(samples), (self.samplerate / self.fc) / 2)
elif self.demodtype == "avg":
het_samples = samples * common.local_carrier(self.fc, len(samples), self.samplerate)
# return self.avgfilter(het_samples, SAMPLES_PER_CARRIER/2)
return self.avgfilter(het_samples, (self.samplerate / self.fc) / 2)
elif self.demodtype == "quad":
"""
A quadrature demodulator.
"""
het_samples = samples * common.local_carrier(self.fc, len(samples), self.samplerate, "demodquad")
# self.plot_sig_spectrum(numpy.real(het_samples),"demodulated samples before LPF - I-branch")
# set the LPF cut-off frequency
omega_lo = 1.5 * math.pi / self.mapper.spb
omega_hi = self.fc * 2 * math.pi / self.samplerate
omega_cut = (self.changap * 2 * math.pi / self.samplerate) / 2.0
print "Rx LPF Cutoff frequency :", omega_cut
demod_filt_out = self.lpfilter(het_samples, omega_cut, "receive LPF")
samples_rx_out = numpy.abs(demod_filt_out)
# self.plot_sig_spectrum(numpy.real(demod_filt_out),
# "demodulated samples after LPF - I-branch")
# p.show()
return samples_rx_out
else:
print "Unsupported demod type"
sys.exit(1)
def modulate(self, samples):
'''
Multiply samples by a local sinusoid carrier of the same length.
Return the multiplied result.
'''
print '\tNumber of samples being sent:', len(samples)
return samples * local_carrier(self.fc, len(samples), self.samplerate)
def modulate(self, samples):
'''
Multiply samples by a local sinusoid carrier of the same length.
Return the multiplied result.
'''
print '\tNumber of samples being sent:', len(samples)
return samples * local_carrier(self.fc, len(samples), self.samplerate)
def detect_energy(self, samples):
zerolen = self.preamble.silence * self.mapper.spb
isamp = samples[:zerolen]
mod_isamp = isamp * common.local_carrier(self.fc, len(isamp), self.samplerate)
noise_mean = numpy.mean(mod_isamp)
noise_std = numpy.std(mod_isamp)
for offset in xrange(len(samples)):
if abs(samples[offset] > noise_mean + 5.0 * noise_std):
break
return offset
def detect_preamble(self, samples):
"""
Preamble detection modulating over carrier (ie, not in baseband).
"""
offset = max(0, self.detect_energy(samples))
print "Some sort of energy detected around sample", offset
barker = self.preamble.barker()
presamples = self.mapper.bits2samples(barker)
mod_presamples = presamples * common.local_carrier(self.fc, len(presamples), self.samplerate)
x = 2 * self.preamble.barkerlen() * self.mapper.spb
return max(0, self.correlate(mod_presamples, samples[max(0, offset - x) : offset + x]))
def modulate(self, samples):
'''
Multiply samples by a local sinusoid carrier of the same length.
Return the multiplied result.
'''
return samples * local_carrier(self.fc, len(samples), self.samplerate)
