1 //
2 // agc_crcf_example.c
3 //
4 // Automatic gain control example demonstrating its transient
5 // response.
6 //
7
8 #include <stdio.h>
9 #include <stdlib.h>
10 #include <math.h>
11 #include <complex.h>
12 #include <getopt.h>
13 #include "liquid.h"
14
15 #define OUTPUT_FILENAME "agc_crcf_example.m"
16
17 // print usage/help message
usage()18 void usage()
19 {
20 printf("agc_example [options]\n");
21 printf(" h : print usage\n");
22 printf(" n : number of samples, n >=100, default: 2000\n");
23 printf(" b : AGC bandwidth, b >= 0, default: 0.01\n");
24 }
25
26
main(int argc,char * argv[])27 int main(int argc, char*argv[])
28 {
29 // options
30 float bt = 0.01f; // agc loop bandwidth
31 float gamma = 0.001f; // initial signal level
32 unsigned int num_samples = 2000; // number of samples
33
34 int dopt;
35 while((dopt = getopt(argc,argv,"hn:N:s:b:")) != EOF){
36 switch (dopt) {
37 case 'h': usage(); return 0;
38 case 'n': num_samples = atoi(optarg); break;
39 case 'b': bt = atof(optarg); break;
40 default:
41 exit(1);
42 }
43 }
44
45 // validate input
46 if (bt < 0.0f) {
47 fprintf(stderr,"error: %s, bandwidth must be positive\n", argv[0]);
48 exit(1);
49 } else if (num_samples == 0) {
50 fprintf(stderr,"error: %s, number of samples must be greater than zero\n", argv[0]);
51 exit(1);
52 }
53
54 unsigned int i;
55
56 // create objects
57 agc_crcf q = agc_crcf_create();
58 agc_crcf_set_bandwidth(q, bt);
59 //agc_crcf_set_scale(q, 0.5f);
60
61 float complex x[num_samples]; // input
62 float complex y[num_samples]; // output
63 float rssi[num_samples]; // received signal strength
64
65 // print info
66 agc_crcf_print(q);
67
68 // generate signal
69 for (i=0; i<num_samples; i++)
70 x[i] = gamma * cexpf(_Complex_I*2*M_PI*0.0193f*i);
71
72 // run agc
73 for (i=0; i<num_samples; i++) {
74 // apply gain
75 agc_crcf_execute(q, x[i], &y[i]);
76
77 // retrieve signal level [dB]
78 rssi[i] = agc_crcf_get_rssi(q);
79 }
80
81 // destroy AGC object
82 agc_crcf_destroy(q);
83
84 //
85 // export results
86 //
87 FILE* fid = fopen(OUTPUT_FILENAME,"w");
88 if (!fid) {
89 fprintf(stderr,"error: %s, could not open '%s' for writing\n", argv[0], OUTPUT_FILENAME);
90 exit(1);
91 }
92 fprintf(fid,"%% %s: auto-generated file\n\n",OUTPUT_FILENAME);
93 fprintf(fid,"clear all;\nclose all;\n\n");
94 fprintf(fid,"n = %u;\n", num_samples);
95
96 for (i=0; i<num_samples; i++) {
97 fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
98 fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
99 fprintf(fid,"rssi(%4u) = %12.4e;\n", i+1, rssi[i]);
100 }
101
102 // plot results
103 fprintf(fid,"\n");
104 fprintf(fid,"figure;\n");
105 fprintf(fid,"t = 0:(n-1);\n");
106 fprintf(fid,"subplot(3,1,1);\n");
107 fprintf(fid," plot(t, real(x), '-', 'Color',[0 0.2 0.5],...\n");
108 fprintf(fid," t, imag(x), '-', 'Color',[0 0.5 0.2]);\n");
109 fprintf(fid," grid on;\n");
110 fprintf(fid," xlabel('sample index');\n");
111 fprintf(fid," ylabel('input');\n");
112 fprintf(fid,"subplot(3,1,2);\n");
113 fprintf(fid," plot(t, real(y), '-', 'Color',[0 0.2 0.5],...\n");
114 fprintf(fid," t, imag(y), '-', 'Color',[0 0.5 0.2]);\n");
115 fprintf(fid," grid on;\n");
116 fprintf(fid," xlabel('sample index');\n");
117 fprintf(fid," ylabel('output');\n");
118 fprintf(fid,"subplot(3,1,3);\n");
119 fprintf(fid," plot(t,rssi,'-','LineWidth',1.2,'Color',[0.5 0 0]);\n");
120 fprintf(fid," grid on;\n");
121 fprintf(fid," xlabel('sample index');\n");
122 fprintf(fid," ylabel('rssi [dB]');\n");
123
124 fclose(fid);
125 printf("results written to %s\n", OUTPUT_FILENAME);
126
127 printf("done.\n");
128 return 0;
129 }
130
131