--- /dev/null
+#
+# Copyright 2008 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.
+#
+
+from gnuradio import gr, eng_notation
+import math
+
+n2s = eng_notation.num_to_str
+
+class receive_path(gr.hier_block2):
+ def __init__(self,
+ if_rate, # Incoming sample rate
+ symbol_rate, # Original symbol rate
+ excess_bw, # RRC excess bandwidth, typically 0.35-0.5
+ costas_alpha, # Costas loop 1st order gain, typically 0.01-0.2
+ costas_beta, # Costas loop 2nd order gain, typically alpha^2/4.0
+ costas_max, # Costas loop max frequency offset in radians/sample
+ mm_gain_mu, # M&M loop 1st order gain, typically 0.001-0.2
+ mm_gain_omega, # M&M loop 2nd order gain, typically alpha^2/4.0
+ mm_omega_limit, # M&M loop max timing error
+ ):
+
+ gr.hier_block2.__init__(self, "receive_path",
+ gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
+ gr.io_signature(0, 0, 0)) # Output signature
+
+ self._if_rate = if_rate
+ self._sps = int(self._if_rate/symbol_rate)
+ print "IF sample rate:", n2s(self._if_rate)
+ print "Symbol rate:", n2s(symbol_rate)
+ print "Samples/symbol:", self._sps
+ print "RRC bandwidth:", excess_bw
+
+ # Create AGC to scale input to unity
+ self._agc = gr.agc_cc(1e-5, 1.0, 1.0, 1.0)
+
+ # Create RRC with specified excess bandwidth
+ taps = gr.firdes.root_raised_cosine(1.0, # Gain
+ self._sps, # Sampling rate
+ 1.0, # Symbol rate
+ excess_bw, # Roll-off factor
+ 11*self._sps) # Number of taps
+
+ self._rrc = gr.fir_filter_ccf(1, taps)
+
+ # Create a Costas loop frequency/phase recovery block
+
+ print "Costas alpha:", costas_alpha
+ print "Costas beta:", costas_beta
+ print "Costas max:", costas_max
+
+ self._costas = gr.costas_loop_cc(costas_alpha, # PLL first order gain
+ costas_beta, # PLL second order gain
+ costas_max, # Max frequency offset rad/sample
+ -costas_max, # Min frequency offset rad/sample
+ 2) # BPSK
+
+ # Create a M&M bit synchronization retiming block
+ mm_mu = 0.5
+ mm_omega = self._sps
+
+ print "MM gain mu:", mm_gain_mu
+ print "MM gain omega:", mm_gain_omega
+ print "MM omega limit:", mm_omega_limit
+
+ self._mm = gr.clock_recovery_mm_cc(mm_omega, # Initial samples/symbol
+ mm_gain_omega, # Second order gain
+ mm_mu, # Initial symbol phase
+ mm_gain_mu, # First order gain
+ mm_omega_limit) # Maximum timing offset
+
+ # Add an SNR probe on the demodulated constellation
+ self._snr_probe = gr.probe_mpsk_snr_c(10.0/symbol_rate)
+ self.connect(self._mm, self._snr_probe)
+
+ # Slice the resulting constellation into bits.
+ # Get inphase channel and make decision about 0
+ self._c2r = gr.complex_to_real()
+ self._slicer = gr.binary_slicer_fb()
+
+ # Descramble BERT sequence. A channel error will create 3 incorrect bits
+ self._descrambler = gr.descrambler_bb(0x8A, 0x7F, 7) # CCSDS 7-bit descrambler
+
+ # Measure BER by the density of 0s in the stream
+ self._ber = gr.probe_density_b(1.0/symbol_rate)
+
+ self.connect(self, self._agc, self._rrc, self._costas, self._mm,
+ self._c2r, self._slicer, self._descrambler, self._ber)
+
+ def frequency_offset(self):
+ return self._costas.freq()*self._if_rate/(2*math.pi)
+
+ def timing_offset(self):
+ return self._mm.omega()/self._sps-1.0
+
+ def snr(self):
+ return self._snr_probe.snr()
+
+ def ber(self):
+ return (1.0-self._ber.density())/3.0
+
projects / debian / gnuradio / blobdiff