www.pudn.com > lib.zip > equalize.C

/* Modem for MIPS   AJF	  October 1996 
   Equalizer routines */ 
 
#include  
#include  
 
#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); 
  }