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//
// agc_crcf_example.c
//
// Automatic gain control example demonstrating its transient
// response.
//
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <complex.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "agc_crcf_example.m"
// print usage/help message
void usage()
{
printf("agc_example [options]\n");
printf(" h : print usage\n");
printf(" n : number of samples, n >=100, default: 2000\n");
printf(" b : AGC bandwidth, b >= 0, default: 0.01\n");
}
int main(int argc, char*argv[])
{
// options
float bt = 0.01f; // agc loop bandwidth
float gamma = 0.001f; // initial signal level
unsigned int num_samples = 2000; // number of samples
int dopt;
while((dopt = getopt(argc,argv,"hn:N:s:b:")) != EOF){
switch (dopt) {
case 'h': usage(); return 0;
case 'n': num_samples = atoi(optarg); break;
case 'b': bt = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (bt < 0.0f) {
fprintf(stderr,"error: %s, bandwidth must be positive\n", argv[0]);
exit(1);
} else if (num_samples == 0) {
fprintf(stderr,"error: %s, number of samples must be greater than zero\n", argv[0]);
exit(1);
}
unsigned int i;
// create objects
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q, bt);
//agc_crcf_set_scale(q, 0.5f);
float complex x[num_samples]; // input
float complex y[num_samples]; // output
float rssi[num_samples]; // received signal strength
// print info
agc_crcf_print(q);
// generate signal
for (i=0; i<num_samples; i++)
x[i] = gamma * cexpf(_Complex_I*2*M_PI*0.0193f*i);
// run agc
for (i=0; i<num_samples; i++) {
// apply gain
agc_crcf_execute(q, x[i], &y[i]);
// retrieve signal level [dB]
rssi[i] = agc_crcf_get_rssi(q);
}
// destroy AGC object
agc_crcf_destroy(q);
//
// export results
//
FILE* fid = fopen(OUTPUT_FILENAME,"w");
if (!fid) {
fprintf(stderr,"error: %s, could not open '%s' for writing\n", argv[0], OUTPUT_FILENAME);
exit(1);
}
fprintf(fid,"%% %s: auto-generated file\n\n",OUTPUT_FILENAME);
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"n = %u;\n", num_samples);
for (i=0; i<num_samples; i++) {
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"rssi(%4u) = %12.4e;\n", i+1, rssi[i]);
}
// plot results
fprintf(fid,"\n");
fprintf(fid,"figure;\n");
fprintf(fid,"t = 0:(n-1);\n");
fprintf(fid,"subplot(3,1,1);\n");
fprintf(fid," plot(t, real(x), '-', 'Color',[0 0.2 0.5],...\n");
fprintf(fid," t, imag(x), '-', 'Color',[0 0.5 0.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('input');\n");
fprintf(fid,"subplot(3,1,2);\n");
fprintf(fid," plot(t, real(y), '-', 'Color',[0 0.2 0.5],...\n");
fprintf(fid," t, imag(y), '-', 'Color',[0 0.5 0.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('output');\n");
fprintf(fid,"subplot(3,1,3);\n");
fprintf(fid," plot(t,rssi,'-','LineWidth',1.2,'Color',[0.5 0 0]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('rssi [dB]');\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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