1 //
2 // firfilt_rrrf_example.c
3 //
4
5 #include <stdio.h>
6 #include <math.h>
7
8 #include "liquid.h"
9
10 #define OUTPUT_FILENAME "firfilt_rrrf_example.m"
11
main()12 int main() {
13 // options
14 unsigned int h_len=27; // filter length
15 float fc=0.1f; // filter cutoff
16 float As=60.0f; // stop-band attenuation [dB]
17 float mu=0.0f; // timing offset
18 unsigned int n=200; // number of random input samples
19
20 // derived values
21 unsigned int num_samples = n + h_len;
22
23 // arrays
24 float x[num_samples]; // filter input
25 float y[num_samples]; // filter output
26
27 unsigned int i;
28 #if 0
29 float h[h_len];
30 liquid_firdes_kaiser(h_len,fc,As,mu,h);
31 firfilt_rrrf f = firfilt_rrrf_create(h,h_len);
32 #else
33 firfilt_rrrf f = firfilt_rrrf_create_kaiser(h_len,fc,As,mu);
34 #endif
35 firfilt_rrrf_print(f);
36
37 for (i=0; i<num_samples; i++) {
38 // generate noise
39 x[i] = (i<n) ? randnf() : 0.0f;
40
41 firfilt_rrrf_push(f, x[i]);
42 firfilt_rrrf_execute(f, &y[i]);
43
44 printf("x[%4u] = %12.8f, y[%4u] = %12.8f;\n", i, x[i], i, y[i]);
45 }
46
47 // destroy filter object
48 firfilt_rrrf_destroy(f);
49
50 //
51 // export results
52 //
53 FILE*fid = fopen(OUTPUT_FILENAME,"w");
54 fprintf(fid,"%% firfilt_rrrf_example.m: auto-generated file\n\n");
55 fprintf(fid,"clear all;\nclose all;\n\n");
56 fprintf(fid,"num_samples=%u;\n", num_samples);
57 fprintf(fid,"x = zeros(1,num_samples);\n");
58 fprintf(fid,"y = zeros(1,num_samples);\n");
59
60 for (i=0; i<num_samples; i++)
61 fprintf(fid,"x(%4u) = %12.4e; y(%4u) = %12.4e;\n", i+1, x[i], i+1, y[i]);
62
63 fprintf(fid,"nfft=512;\n");
64 fprintf(fid,"X=20*log10(abs(fftshift(fft(x/sqrt(num_samples),nfft))));\n");
65 fprintf(fid,"Y=20*log10(abs(fftshift(fft(y/sqrt(num_samples),nfft))));\n");
66 fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
67 fprintf(fid,"t=[0:(num_samples-1)];\n");
68 fprintf(fid,"figure;\n");
69 fprintf(fid,"subplot(2,1,1);\n");
70 fprintf(fid," plot(t,x,'Color',[0.3 0.3 0.3],...\n");
71 fprintf(fid," t,y,'LineWidth',2);\n");
72 fprintf(fid," grid on;\n");
73 fprintf(fid," xlabel('time');\n");
74 fprintf(fid," ylabel('signals');\n");
75 fprintf(fid," axis([0 num_samples -4 4]);\n");
76 fprintf(fid," legend('noise','filtered noise',1);");
77 fprintf(fid,"subplot(2,1,2);\n");
78 fprintf(fid," plot(f,X,'Color',[0.3 0.3 0.3],...\n");
79 fprintf(fid," f,Y,'LineWidth',2);\n");
80 fprintf(fid," grid on;\n");
81 fprintf(fid," xlabel('normalized frequency');\n");
82 fprintf(fid," ylabel('PSD [dB]');\n");
83 fprintf(fid," axis([-0.5 0.5 -80 40]);\n");
84 fprintf(fid," legend('noise','filtered noise',1);");
85
86 fclose(fid);
87 printf("results written to %s\n", OUTPUT_FILENAME);
88
89 printf("done.\n");
90 return 0;
91 }
92
93