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 // ------------------------------------------------------------------------
77 double d_last_slant_range;
80 aux_state(dyn_object *obj) : d_obj(obj) {}
83 // ------------------------------------------------------------------------
85 class my_sim : public simulation
89 unsigned long long d_pos; // position in time series
91 dyn_object *d_tx; // transmitter (not moving)
92 dyn_object *d_rx0; // receiver (not moving)
93 std::vector<aux_state*> d_target;
95 double d_baseline; // length of baseline in meters
96 double d_range_bin; // meters/range_bin
97 float d_tx_lambda; // wavelength of tx signals in meters
99 float d_gain; // linear scale factor
101 void adjust_for_start_time(double start_time);
103 bool write_output(gr_complex x)
105 return fwrite(&x, sizeof(x), 1, d_output) == 1;
109 my_sim(FILE *output, time_series &ref, double timestep, float sample_rate,
110 double start_time, double tx_freq, double gain_db);
114 bool run(long long nsteps);
118 my_sim::my_sim(FILE *output, time_series &ref, double timestep,
119 float sample_rate, double start_time,
120 double tx_freq, double gain_db)
121 : simulation(timestep),
122 d_output(output), d_ref(ref), d_pos(0), d_z(1024),
123 d_range_bin(C * timestep), d_tx_lambda(C/tx_freq),
124 d_sample_rate(sample_rate), d_gain(exp10(gain_db/10))
126 d_tx = new dyn_object(point(0,0), point(0,0), "Tx");
127 d_rx0 = new dyn_object(point(45e3,0), point(0,0), "Rx0");
131 d_baseline = dyn_object::distance(*d_tx, *d_rx0);
135 float aircraft_speed;
136 float aircraft_angle;
141 aircraft_speed = 135; // m/s
142 aircraft_angle = 240 * M_PI/180;
143 aircraft_pos = point(55e3, 20e3);
145 ac = new dyn_object(aircraft_pos,
146 point(aircraft_speed * cos(aircraft_angle),
147 aircraft_speed * sin(aircraft_angle)),
150 d_target.push_back(new aux_state(ac));
153 aircraft_speed = 350; // m/s
154 aircraft_angle = 0 * M_PI/180;
155 aircraft_pos = point(-20e3, 60e3);
157 ac = new dyn_object(aircraft_pos,
158 point(aircraft_speed * cos(aircraft_angle),
159 aircraft_speed * sin(aircraft_angle)),
162 d_target.push_back(new aux_state(ac));
165 adjust_for_start_time(start_time);
167 for (unsigned i = 0; i < d_target.size(); i++)
168 d_target[i]->d_last_slant_range =
169 (dyn_object::distance(*d_tx, *d_target[i]->d_obj)
170 + dyn_object::distance(*d_target[i]->d_obj, *d_rx0));
179 my_sim::adjust_for_start_time(double start_time)
181 for (unsigned i = 0; i < d_obj.size(); i++){
182 // Adjust initial starting positions depending on simulation
183 // start time. FIXME Assumes velocity is constant
184 point p = d_obj[i]->pos();
185 point v = d_obj[i]->vel();
186 p.set_x(p.x() + v.x() * start_time);
187 p.set_y(p.y() + v.y() * start_time);
188 d_obj[i]->set_pos(p);
195 // std::cout << *d_ac0 << std::endl;
197 // grab new item from input and insert it into delay line
198 const gr_complex *in = (const gr_complex *) d_ref.seek(d_pos++, 1);
203 gr_complex s = 0; // output sample
204 // FIXME ought to add in attenuated direct path input
207 // for each target, compute slant_range and slant_range'
209 for (unsigned i = 0; i < d_target.size(); i++){
210 aux_state *t = d_target[i];
213 (dyn_object::distance(*d_tx, *t->d_obj)
214 + dyn_object::distance(*t->d_obj, *d_rx0)); // meters
216 double delta_slant_range = slant_range - t->d_last_slant_range;
217 t->d_last_slant_range = slant_range;
218 double deriv_slant_range_wrt_time = delta_slant_range / timestep(); // m/sec
220 //fprintf(stdout, "%10.3f\t%10.3f\n", slant_range, deriv_slant_range_wrt_time);
222 // FIXME, may want to interpolate between two bins.
223 int int_delay = lrint((slant_range - d_baseline) / d_range_bin);
225 gr_complex x = d_z.ref_item(int_delay);
227 // scale amplitude (this includes everything: RCS, antenna gain, losses, etc...)
231 // compute doppler and apply it
232 float f_doppler = -deriv_slant_range_wrt_time / d_tx_lambda;
234 t->d_nco.set_freq(f_doppler / d_sample_rate);
235 gr_complex phasor(t->d_nco.cos(), t->d_nco.sin());
240 s += x; // add in this target's contribution
245 return simulation::update(); // run generic update
249 my_sim::run(long long nsteps)
251 //fprintf(stdout, "<%12.2f, %12.2f>\n", d_ac0->pos().x(), d_ac0->pos().y());
252 //std::cout << *d_ac0 << std::endl;
253 bool ok = simulation::run(nsteps);
254 //std::cout << *d_ac0 << std::endl;
255 //fprintf(stdout, "<%12.2f, %12.2f>\n", d_ac0->pos().x(), d_ac0->pos().y());
259 // ------------------------------------------------------------------------
262 usage(const char *argv0)
264 const char *progname;
265 const char *t = std::strrchr(argv0, '/');
271 fprintf(stderr, "usage: %s [options] ref_file\n", progname);
272 fprintf(stderr, " -o OUTPUT_FILENAME [default=sim.dat]\n");
273 fprintf(stderr, " -n NSAMPLES_TO_PRODUCE [default=+inf]\n");
274 fprintf(stderr, " -s NSAMPLES_TO_SKIP [default=0]\n");
275 fprintf(stderr, " -g reflection gain in dB (should be <= 0) [default=0]\n");
276 fprintf(stderr, " -f transmitter freq in Hz [default=100MHz]\n");
277 fprintf(stderr, " -r sample rate in Hz [default=250kHz]\n");
278 fprintf(stderr, " -S simulation start time in seconds [default=0]\n");
282 main(int argc, char **argv)
285 const char *output_filename = "sim.dat";
286 const char *ref_filename = 0;
287 long long int nsamples_to_skip = 0;
288 long long int nsamples_to_produce = std::numeric_limits<long long int>::max();
289 double sample_rate = 250e3;
291 double tx_freq = 100e6;
292 double start_time = 0;
294 while ((ch = getopt(argc, argv, "o:s:n:g:f:S:")) != -1){
297 output_filename = optarg;
301 nsamples_to_skip = (long long) strtod(optarg, 0);
302 if (nsamples_to_skip < 0){
304 fprintf(stderr, " nsamples_to_skip must be >= 0\n");
310 nsamples_to_produce = (long long) strtod(optarg, 0);
311 if (nsamples_to_produce < 0){
313 fprintf(stderr, " nsamples_to_produce must be >= 0\n");
319 gain_db = strtod(optarg, 0);
323 tx_freq = strtod(optarg, 0);
327 sample_rate = strtod(optarg, 0);
331 start_time = strtod(optarg, 0);
342 if (argc - optind != 1){
347 ref_filename = argv[optind++];
349 double timestep = 1.0/sample_rate;
352 FILE *output = fopen(output_filename, "wb");
354 perror(output_filename);
358 unsigned long long ref_starting_offset = 0;
359 ref_starting_offset += nsamples_to_skip;
362 time_series ref(sizeof(gr_complex), ref_filename, ref_starting_offset, 0);
364 my_sim simulator(output, ref, timestep, sample_rate, start_time,
366 simulator.run(nsamples_to_produce);
368 catch (std::string &s){
369 std::cerr << s << std::endl;