| #!/usr/bin/env python |
| # -*- coding: utf-8 -*- |
| # |
| # Copyright 2014 Piotr Krysik <ptrkrysik@gmail.com> |
| # |
| # This 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. |
| # |
| # This software 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 this software; see the file COPYING. If not, write to |
| # the Free Software Foundation, Inc., 51 Franklin Street, |
| # Boston, MA 02110-1301, USA. |
| # |
| |
| from numpy import * |
| #from pylab import * |
| from gnuradio import gr |
| import pmt |
| from grgsm.chirpz import ZoomFFT |
| |
| class fcch_burst_tagger(gr.sync_block): |
| """ |
| docstring for block fcch_burst_tagger |
| """ |
| def __init__(self, OSR): |
| gr.sync_block.__init__(self, |
| name="fcch_burst_tagger", |
| in_sig=[complex64, float32], |
| out_sig=[complex64]) |
| |
| self.state=False |
| self.symbol_rate = 1625000/6 |
| self.OSR=OSR |
| self.samp_rate = self.symbol_rate*OSR |
| self.burst_size = int(156.25*self.OSR) |
| self.guard_period = int(round(8.25*self.OSR)) |
| self.block_size = self.burst_size+self.guard_period |
| self.processed_block_size = int(142*self.OSR) |
| self.set_history(self.block_size) |
| self.set_output_multiple(self.guard_period) |
| self.prev_offset=0 |
| |
| #parameters of zoomfft frequency estimator |
| f1 = self.symbol_rate/4*0.9 |
| f2 = self.symbol_rate/4*1.1 |
| m=5000*self.OSR |
| self.zoomfft = ZoomFFT(self.processed_block_size, f1, f2, m, Fs=self.samp_rate) |
| self.f_axis = linspace(f1,f2,m) |
| |
| def work(self, input_items, output_items): |
| in0=input_items[0] |
| output_items[0][:] = in0[self.history()-1:] |
| |
| threshold = input_items[1][self.history()-1:] |
| threshold_diff = diff(concatenate([[0],threshold])) |
| up_to_high_indexes = nonzero(threshold_diff>0)[0] |
| |
| up_to_high_idx=[] |
| |
| for up_to_high_idx in up_to_high_indexes: #look for "high" value at the trigger |
| if up_to_high_idx==0 and self.state==True: #if it's not transition from "low" to "high" |
| continue #then continue |
| self.state=True #if found - change state |
| |
| if self.state==True and up_to_high_idx and any(threshold_diff<0): #and look for transition from high to low |
| last_up_to_high_idx = up_to_high_idx |
| last_high_to_low_idx = nonzero(threshold_diff<0)[0][-1] |
| |
| if last_high_to_low_idx-last_up_to_high_idx>0: |
| coarse_idx = int(last_high_to_low_idx+self.history()-self.block_size) |
| inst_freq = angle(in0[coarse_idx:coarse_idx+self.block_size]*in0[coarse_idx-self.OSR:coarse_idx+self.block_size-self.OSR].conj())/(2*pi)*self.symbol_rate #instantaneus frequency estimate |
| precise_idx = self.find_best_position(inst_freq) |
| # measured_freq = mean(inst_freq[precise_idx:precise_idx+self.processed_block_size]) |
| expected_freq = self.symbol_rate/4 |
| |
| print "input_items:",len(in0) |
| print "coarse_idx",coarse_idx |
| print "coarse_idx+precise_idx",coarse_idx+precise_idx |
| |
| zoomed_spectrum = abs(self.zoomfft(in0[coarse_idx+precise_idx:coarse_idx+precise_idx+self.processed_block_size])) |
| measured_freq = self.f_axis[argmax(zoomed_spectrum)] |
| freq_offset = measured_freq - expected_freq |
| offset = self.nitems_written(0) + coarse_idx + precise_idx - self.guard_period |
| key = pmt.string_to_symbol("fcch") |
| value = pmt.from_double(freq_offset) |
| self.add_item_tag(0,offset, key, value) |
| self.state=False |
| |
| # Some additional plots and prints for debugging |
| # print "coarse_idx+precise_idx",coarse_idx+precise_idx |
| # print "offset-self.nitems_written(0):",offset-self.nitems_written(0) |
| print offset-self.prev_offset |
| self.prev_offset=offset |
| print "freq offset", freq_offset |
| # freq_offset = measured_freq - expected_freq |
| # plot(self.f_axis, zoomed_spectrum) |
| # show() |
| # plot(inst_freq[precise_idx:precise_idx+self.burst_size]) |
| # show() |
| # plot(unwrap(angle(in0[coarse_idx+precise_idx:coarse_idx+precise_idx+self.burst_size]))) |
| # show() |
| # |
| return len(output_items[0]) |
| |
| def find_best_position(self, inst_freq): |
| lowest_max_min_diff = 1e6 #1e6 - just some large value |
| start_pos = 0 |
| |
| for ii in xrange(0,int(2*self.guard_period)): |
| min_inst_freq = min(inst_freq[ii:self.processed_block_size+ii-1]); |
| max_inst_freq = max(inst_freq[ii:self.processed_block_size+ii-1]); |
| |
| if (lowest_max_min_diff > max_inst_freq - min_inst_freq): |
| lowest_max_min_diff = max_inst_freq - min_inst_freq; |
| start_pos = ii |
| # print 'start_pos',start_pos |
| |
| # plot(xrange(start_pos,start_pos+self.processed_block_size),inst_freq[start_pos:start_pos+self.processed_block_size],'r.') |
| # hold(True) |
| # plot(inst_freq) |
| # show() |
| |
| return start_pos |