1 //
2 // firinterp_crcf_example.c
3 //
4 // This example demonstrates the firinterp object (interpolator) interface.
5 // Data symbols are generated and then interpolated according to a
6 // finite impulse response Nyquist filter.
7 //
8
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <math.h>
12 #include <getopt.h>
13
14 #include "liquid.h"
15
16 #define OUTPUT_FILENAME "firinterp_crcf_example.m"
17
18 // print usage/help message
usage()19 void usage()
20 {
21 printf("firinterp_crcf_example:\n");
22 printf(" -h : print usage/help\n");
23 printf(" -k <s/sym> : samples/symbol (interp factor), k > 1, default: 4\n");
24 printf(" -m <delay> : filter delay (symbols), m > 0, default: 3\n");
25 printf(" -s <atten> : filter stop-band attenuation [dB], default: 60\n");
26 printf(" -n <num> : number of data symbols, default: 16\n");
27 }
28
29
main(int argc,char * argv[])30 int main(int argc, char*argv[]) {
31 // options
32 unsigned int k = 4; // samples/symbol
33 unsigned int m = 3; // filter delay
34 float As = 60.0f; // filter stop-band attenuation
35 unsigned int num_syms = 16; // number of data symbols
36
37 int dopt;
38 while ((dopt = getopt(argc,argv,"uhk:m:s:n:")) != EOF) {
39 switch (dopt) {
40 case 'u':
41 case 'h': usage(); return 0;
42 case 'k': k = atoi(optarg); break;
43 case 'm': m = atoi(optarg); break;
44 case 's': As = atof(optarg); break;
45 case 'n': num_syms = atoi(optarg); break;
46 default:
47 exit(1);
48 }
49 }
50
51 // validate options
52 if (k < 2) {
53 fprintf(stderr,"error: %s, interp factor must be greater than 1\n", argv[0]);
54 exit(1);
55 } else if (m < 1) {
56 fprintf(stderr,"error: %s, filter delay must be greater than 0\n", argv[0]);
57 exit(1);
58 } else if (num_syms < 1) {
59 fprintf(stderr,"error: %s, must have at least one data symbol\n", argv[0]);
60 usage();
61 return 1;
62 }
63
64 // derived values
65 unsigned int num_syms_total = num_syms + 2*m; // total symbols (w/ delay)
66 unsigned int num_samples = k*num_syms_total; // total samples
67
68 // create interpolator from prototype
69 firinterp_crcf q = firinterp_crcf_create_kaiser(k,m,As);
70
71 // generate input signal and interpolate
72 float complex x[num_syms_total]; // input symbols
73 float complex y[num_samples]; // output samples
74 unsigned int i;
75 for (i=0; i<num_syms; i++) {
76 x[i] = (rand() % 2 ? 1.0f : -1.0f) +
77 (rand() % 2 ? 1.0f : -1.0f) * _Complex_I;
78 }
79
80 // pad end of sequence with zeros
81 for (i=num_syms; i<num_syms_total; i++)
82 x[i] = 0.0f;
83
84 // interpolate symbols
85 for (i=0; i<num_syms_total; i++)
86 firinterp_crcf_execute(q, x[i], &y[k*i]);
87
88 // destroy interpolator object
89 firinterp_crcf_destroy(q);
90
91 // print results to screen
92 printf("x(t) :\n");
93 for (i=0; i<num_syms_total; i++)
94 printf(" x(%4u) = %8.4f + j*%8.4f;\n", i, crealf(x[i]), cimagf(x[i]));
95
96 printf("y(t) :\n");
97 for (i=0; i<num_samples; i++) {
98 printf(" y(%4u) = %8.4f + j*%8.4f;", i, crealf(y[i]), cimagf(y[i]));
99 if ( (i >= k*m) && ((i%k)==0))
100 printf(" **\n");
101 else
102 printf("\n");
103 }
104
105 //
106 // export output file
107 //
108 FILE * fid = fopen(OUTPUT_FILENAME,"w");
109 fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
110 fprintf(fid,"clear all;\n");
111 fprintf(fid,"close all;\n");
112 fprintf(fid,"k = %u;\n", k);
113 fprintf(fid,"m = %u;\n", m);
114 fprintf(fid,"num_syms_total = %u;\n", num_syms_total);
115 fprintf(fid,"num_samples = k*num_syms_total;\n");
116 fprintf(fid,"x = zeros(1,num_syms_total);\n");
117 fprintf(fid,"y = zeros(1,num_samples);\n");
118
119 for (i=0; i<num_syms_total; i++)
120 fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
121
122 for (i=0; i<num_samples; i++)
123 fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
124
125 fprintf(fid,"\n\n");
126 fprintf(fid,"tx = [0:(num_syms_total-1)];\n");
127 fprintf(fid,"ty = [0:(num_samples-1)]/k - m;\n");
128 fprintf(fid,"figure;\n");
129 fprintf(fid,"subplot(2,1,1);\n");
130 fprintf(fid," plot(ty,real(y),'-',tx,real(x),'s');\n");
131 fprintf(fid," xlabel('time');\n");
132 fprintf(fid," ylabel('real');\n");
133 fprintf(fid," grid on;\n");
134 fprintf(fid,"subplot(2,1,2);\n");
135 fprintf(fid," plot(ty,imag(y),'-',tx,imag(x),'s');\n");
136 fprintf(fid," xlabel('time');\n");
137 fprintf(fid," ylabel('imag');\n");
138 fprintf(fid," grid on;\n");
139
140 fclose(fid);
141 printf("results written to %s.\n",OUTPUT_FILENAME);
142
143 printf("done.\n");
144 return 0;
145 }
146