1 //
2 // firpfbch2_crcf_example.c
3 //
4 // Example of the finite impulse response (FIR) polyphase filterbank
5 // (PFB) channelizer with an output rate of 2 Fs / M as an (almost)
6 // perfect reconstructive system.
7 //
8
9 #include <stdio.h>
10 #include <stdlib.h>
11 #include <math.h>
12 #include <getopt.h>
13 #include <assert.h>
14
15 #include "liquid.h"
16
17 #define OUTPUT_FILENAME "firpfbch2_crcf_example.m"
18
19 // print usage/help message
usage()20 void usage()
21 {
22 printf("%s [options]\n", __FILE__);
23 printf(" h : print help\n");
24 printf(" M : number of channels, default: 6\n");
25 printf(" m : prototype filter semi-length, default: 4\n");
26 printf(" s : prototype filter stop-band attenuation, default: 80\n");
27 printf(" n : number of 'symbols' to analyze, default: 20\n");
28 }
29
main(int argc,char * argv[])30 int main(int argc, char*argv[])
31 {
32 // options
33 unsigned int num_channels=6; // number of channels
34 unsigned int m = 4; // filter semi-length (symbols)
35 unsigned int num_symbols=20; // number of symbols
36 float As = 80.0f; // filter stop-band attenuation
37
38 int dopt;
39 while ((dopt = getopt(argc,argv,"hM:m:s:n:")) != EOF) {
40 switch (dopt) {
41 case 'h': usage(); return 0;
42 case 'M': num_channels = atoi(optarg); break;
43 case 'm': m = atoi(optarg); break;
44 case 's': As = atof(optarg); break;
45 case 'n': num_symbols = atof(optarg); break;
46 default:
47 exit(1);
48 }
49 }
50
51 unsigned int i;
52
53 // validate input
54 if (num_channels < 2 || num_channels % 2) {
55 fprintf(stderr,"error: %s, number of channels must be greater than 2 and even\n", argv[0]);
56 exit(1);
57 } else if (m == 0) {
58 fprintf(stderr,"error: %s, filter semi-length must be greater than zero\n", argv[0]);
59 exit(1);
60 } else if (num_symbols == 0) {
61 fprintf(stderr,"error: %s, number of symbols must be greater than zero", argv[0]);
62 exit(1);
63 }
64
65 // derived values
66 unsigned int num_samples = num_channels * num_symbols;
67
68 // allocate arrays
69 float complex x[num_samples];
70 float complex y[num_samples];
71
72 // generate input signal
73 for (i=0; i<num_samples; i++) {
74 //x[i] = (i==0) ? 1.0f : 0.0f;
75 x[i] = cexpf( (-0.05f + 0.07f*_Complex_I)*i ); // decaying complex exponential
76 }
77
78 // create filterbank objects from prototype
79 firpfbch2_crcf qa = firpfbch2_crcf_create_kaiser(LIQUID_ANALYZER, num_channels, m, As);
80 firpfbch2_crcf qs = firpfbch2_crcf_create_kaiser(LIQUID_SYNTHESIZER, num_channels, m, As);
81 firpfbch2_crcf_print(qa);
82 firpfbch2_crcf_print(qs);
83
84 // run channelizer
85 float complex Y[num_channels];
86 for (i=0; i<num_samples; i+=num_channels/2) {
87 // run analysis filterbank
88 firpfbch2_crcf_execute(qa, &x[i], Y);
89
90 // run synthesis filterbank
91 firpfbch2_crcf_execute(qs, Y, &y[i]);
92 }
93
94 // destroy filterbank objects
95 firpfbch2_crcf_destroy(qa); // analysis filterbank
96 firpfbch2_crcf_destroy(qs); // synthesis filterbank
97
98 // print output
99 for (i=0; i<num_samples; i++)
100 printf("%4u : %12.8f + %12.8fj\n", i, crealf(y[i]), cimagf(y[i]));
101
102 // compute RMSE
103 float rmse = 0.0f;
104 unsigned int delay = 2*num_channels*m - num_channels/2 + 1;
105 for (i=0; i<num_samples; i++) {
106 float complex err = y[i] - (i < delay ? 0.0f : x[i-delay]);
107 rmse += crealf( err*conjf(err) );
108 }
109 rmse = sqrtf( rmse/(float)num_samples );
110 printf("rmse : %12.4e\n", rmse);
111
112 //
113 // EXPORT DATA TO FILE
114 //
115 FILE * fid = fopen(OUTPUT_FILENAME,"w");
116 fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
117 fprintf(fid,"clear all;\n");
118 fprintf(fid,"close all;\n");
119 fprintf(fid,"num_channels=%u;\n", num_channels);
120 fprintf(fid,"m = %u;\n", m);
121 fprintf(fid,"num_symbols=%u;\n", num_symbols);
122 fprintf(fid,"num_samples = num_channels*num_symbols;\n");
123
124 fprintf(fid,"x = zeros(1,num_samples);\n");
125 fprintf(fid,"y = zeros(1,num_samples);\n");
126
127 // save input and output arrays
128 for (i=0; i<num_samples; i++) {
129 fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimag(x[i]));
130 fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimag(y[i]));
131 }
132
133 // save error vector
134 for (i=delay; i<num_samples; i++) {
135 float complex e = y[i] - x[i-delay];
136 fprintf(fid,"e(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(e), cimag(e));
137 }
138
139 // plot results
140 fprintf(fid,"t = 0:(num_samples-1);\n");
141 fprintf(fid,"delay = %u;\n", delay);
142 fprintf(fid,"figure;\n");
143 fprintf(fid,"title('composite');\n");
144 fprintf(fid,"subplot(3,1,1);\n");
145 fprintf(fid," plot(t,real(x), t-delay,real(y),'s','MarkerSize',1);\n");
146 fprintf(fid," axis([-2 num_samples -0.3 1.1]);\n");
147 fprintf(fid," ylabel('real');\n");
148 fprintf(fid," legend('original','reconstructed','location','northeast');\n");
149 fprintf(fid," grid on;\n");
150 fprintf(fid,"subplot(3,1,2);\n");
151 fprintf(fid," plot(t,imag(x), t-delay,imag(y),'s','MarkerSize',1);\n");
152 fprintf(fid," axis([-2 num_samples -0.3 1.1]);\n");
153 fprintf(fid," ylabel('imag');\n");
154 fprintf(fid," grid on;\n");
155 fprintf(fid,"subplot(3,1,3);\n");
156 fprintf(fid," plot(t-delay,real(e), t-delay,imag(e));\n");
157 fprintf(fid," emax = 1.2*max(abs(e));\n");
158 fprintf(fid," axis([-2 num_samples -emax emax]);\n");
159 fprintf(fid," legend('real','imag','location','northeast');\n");
160 fprintf(fid," xlabel('time');\n");
161 fprintf(fid," ylabel('error');\n");
162 fprintf(fid," grid on;\n");
163
164 fclose(fid);
165 printf("results written to '%s'\n", OUTPUT_FILENAME);
166
167 printf("done.\n");
168 return 0;
169 }
170