?? equalize.c
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/* Modem for MIPS AJF October 1996
Equalizer routines */
#include <stdio.h>
#include <string.h>
#include "private.h"
#include "complex.h"
#include "equalize.h"
void equalizer::reset()
{ for (int i = 0; i < 2*np+1; i++) coeffs[i] = 0.0;
coeffs[np] = 1.0;
for (int i = 0; i < size; i++) in[i] = 0.0;
next = 0;
}
void equalizer::insert(complex z)
{ /* circular buffer */
in[next] = z;
if (++next >= size) next = 0;
}
complex equalizer::get()
{ /* get equalized value */
complex z = 0.0; int ncs = 2*np+1;
for (int i = 0; i < ncs; i++)
{ int p = (next+i) & (size-1);
z += coeffs[i] * in[p];
}
return z;
}
void equalizer::upd(complex eps, int n)
{ complex deps = (delta / (2*n+1)) * eps;
for (int i = np-n; i <= np+n; i++)
{ int p = (next+i) & (size-1);
coeffs[i] += deps * cconj(in[p]);
}
}
int equalizer::getdt()
{ int k1 = 0, k2 = 2*np;
float p1 = 0.0, p2 = 0.0; /* total power to left of k1, right of k2 */
while (k1 < k2)
{ if (p1 > p2) p2 += power(coeffs[k2--]);
else p1 += power(coeffs[k1++]);
}
return k1-np; /* return timing (sample point) error, in units of half a symbol */
}
void equalizer::shift(int dt)
{ int ncs = 2*np+1;
if (dt > 0)
{ memmove(&coeffs[dt], &coeffs[0], (ncs-dt) * sizeof(complex));
memset(&coeffs[0], 0, dt * sizeof(complex));
}
if (dt < 0)
{ dt = -dt;
memmove(&coeffs[0], &coeffs[dt], (ncs-dt) * sizeof(complex));
memset(&coeffs[ncs-dt], 0, dt * sizeof(complex));
}
}
void equalizer::print(char *fn)
{ FILE *fi = fopen(fn, "w");
if (fi != NULL)
{ fprintf(fi, ".sp 0.5i\n.G1 8i\n");
fprintf(fi, "new solid\n");
for (int j = -np; j <= +np; j++) fprintf(fi, "%d %g\n", j, coeffs[np+j].re);
fprintf(fi, "new dashed\n");
for (int j = -np; j <= +np; j++) fprintf(fi, "%d %g\n", j, coeffs[np+j].im);
fprintf(fi, "new dotted\n");
for (int j = -np; j <= +np; j++) fprintf(fi, "%d %g\n", j, power(coeffs[np+j]));
fprintf(fi, ".G2\n.bp\n");
for (int j = -np; j <= +np; j++) fprintf(fi, "{ %10.6f, %10.6f },\n", coeffs[np+j].re, coeffs[np+j].im);
fclose(fi);
}
else fprintf(stderr, "can't create %s\n", fn);
}
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