3 * Copyright 2005 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
7 * GNU Radio is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2, or (at your option)
12 * GNU Radio is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with GNU Radio; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
35 #include <gr_complex.h>
39 #include <gr_fxpt_nco.h>
40 #include "time_series.h"
41 #include "simulation.h"
43 static const double C = 3e8; // sped of light, m/s
46 // ------------------------------------------------------------------------
49 std::vector<gr_complex> d_z;
53 delay_line(unsigned int max_delay)
54 : d_z(gr_rounduppow2(max_delay)), d_mask(d_z.size()-1), d_newest(0)
59 push_item(gr_complex x)
61 d_newest = (d_newest - 1) & d_mask;
66 ref_item(int delay) const
68 return d_z[(d_newest + delay) & d_mask];
72 // ------------------------------------------------------------------------
74 class my_sim : public simulation
78 unsigned long long d_pos; // position in time series
80 dyn_object *d_tx; // transmitter (not moving)
81 dyn_object *d_rx0; // receiver (not moving)
82 dyn_object *d_ac0; // aircraft (linear motion)
85 double d_baseline; // length of baseline in meters
86 double d_last_slant_range;
87 double d_range_bin; // meters/range_bin
88 float d_tx_lambda; // wavelength of tx signals in meters
90 float d_gain; // linear scale factor
93 my_sim(FILE *output, time_series &ref, double timestep, float sample_rate,
94 double tx_freq, double gain_db);
98 bool run(long long nsteps);
100 bool write_output(gr_complex x)
102 return fwrite(&x, sizeof(x), 1, d_output) == 1;
106 my_sim::my_sim(FILE *output, time_series &ref, double timestep,
107 float sample_rate, double tx_freq, double gain_db)
108 : simulation(timestep),
109 d_output(output), d_ref(ref), d_pos(0), d_z(1024),
110 d_range_bin(C * timestep), d_tx_lambda(C/tx_freq),
111 d_sample_rate(sample_rate), d_gain(exp10(gain_db/10))
113 d_tx = new dyn_object(point(0,0), point(0,0), "Tx");
114 d_rx0 = new dyn_object(point(45e3,0), point(0,0), "Rx0");
116 //float aircraft_speed = 135; // meters/sec (~ 300 miles/hr)
117 float aircraft_speed = 350; // meters/sec (~ 750 miles/hr)
118 float aircraft_angle = 250 * M_PI/180;
119 //point aircraft_pos = point(55e3, 20e3);
120 point aircraft_pos = point(55e3-5.54e3, 20e3-15.23e3);
121 d_ac0 = new dyn_object(aircraft_pos,
122 point(aircraft_speed * cos(aircraft_angle),
123 aircraft_speed * sin(aircraft_angle)),
129 d_baseline = dyn_object::distance(*d_tx, *d_rx0);
131 dyn_object::distance(*d_tx, *d_ac0) + dyn_object::distance(*d_ac0, *d_rx0);
141 // std::cout << *d_ac0 << std::endl;
143 // compute slant_range and slant_range'
145 dyn_object::distance(*d_tx, *d_ac0) + dyn_object::distance(*d_ac0, *d_rx0); // meters
146 double delta_slant_range = slant_range - d_last_slant_range;
147 d_last_slant_range = slant_range;
148 double deriv_slant_range_wrt_time = delta_slant_range / timestep(); // m/sec
150 // fprintf(stdout, "%10.3f\t%10.3f\n", slant_range, deriv_slant_range_wrt_time);
152 // grab new item from input and insert it into delay line
153 const gr_complex *in = (const gr_complex *) d_ref.seek(d_pos++, 1);
158 // FIXME, may want to interpolate between two bins.
159 int int_delay = lrint((slant_range - d_baseline) / d_range_bin);
161 gr_complex x = d_z.ref_item(int_delay);
163 x = x * d_gain; // scale amplitude (this includes everything: RCS, antenna gain, losses, etc...)
165 // compute doppler and apply it
166 float f_doppler = -deriv_slant_range_wrt_time / d_tx_lambda;
167 fprintf(stdout, "f_dop: %10.3f\n", f_doppler);
169 d_nco0.set_freq(f_doppler / d_sample_rate);
170 gr_complex phasor(d_nco0.cos(), d_nco0.sin());
176 return simulation::update(); // run generic update
180 my_sim::run(long long nsteps)
182 //fprintf(stdout, "<%12.2f, %12.2f>\n", d_ac0->pos().x(), d_ac0->pos().y());
183 //std::cout << *d_ac0 << std::endl;
184 bool ok = simulation::run(nsteps);
185 //std::cout << *d_ac0 << std::endl;
186 //fprintf(stdout, "<%12.2f, %12.2f>\n", d_ac0->pos().x(), d_ac0->pos().y());
190 // ------------------------------------------------------------------------
193 usage(const char *argv0)
195 const char *progname;
196 const char *t = std::strrchr(argv0, '/');
202 fprintf(stderr, "usage: %s [options] ref_file\n", progname);
203 fprintf(stderr, " -o OUTPUT_FILENAME [default=sim.dat]\n");
204 fprintf(stderr, " -n NSAMPLES_TO_PRODUCE [default=+inf]\n");
205 fprintf(stderr, " -s NSAMPLES_TO_SKIP [default=0]\n");
206 fprintf(stderr, " -g reflection gain in dB (should be <= 0) [default=0]\n");
207 fprintf(stderr, " -f transmitter freq in Hz [default=100MHz]\n");
208 fprintf(stderr, " -r sample rate in Hz [default=250kHz]\n");
212 main(int argc, char **argv)
215 const char *output_filename = "sim.dat";
216 const char *ref_filename = 0;
217 long long int nsamples_to_skip = 0;
218 long long int nsamples_to_produce = std::numeric_limits<long long int>::max();
219 double sample_rate = 250e3;
221 double tx_freq = 100e6;
223 while ((ch = getopt(argc, argv, "o:s:n:g:f:")) != -1){
226 output_filename = optarg;
230 nsamples_to_skip = (long long) strtod(optarg, 0);
231 if (nsamples_to_skip < 0){
233 fprintf(stderr, " nsamples_to_skip must be >= 0\n");
239 nsamples_to_produce = (long long) strtod(optarg, 0);
240 if (nsamples_to_produce < 0){
242 fprintf(stderr, " nsamples_to_produce must be >= 0\n");
248 gain_db = strtod(optarg, 0);
252 tx_freq = strtod(optarg, 0);
256 sample_rate = strtod(optarg, 0);
267 if (argc - optind != 1){
272 ref_filename = argv[optind++];
274 double timestep = 1.0/sample_rate;
277 FILE *output = fopen(output_filename, "wb");
279 perror(output_filename);
283 unsigned long long ref_starting_offset = 0;
284 ref_starting_offset += nsamples_to_skip;
287 time_series ref(sizeof(gr_complex), ref_filename, ref_starting_offset, 0);
289 my_sim simulator(output, ref, timestep, sample_rate, tx_freq, gain_db);
290 simulator.run(nsamples_to_produce);
292 catch (std::string &s){
293 std::cerr << s << std::endl;