farrow.h

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// 
// author="Tony Kirke"
// Copyright(c) 1993-1996 Tony Kirke
/*
 * SPUC - Signal processing using C++ - A DSP library
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef FARROW
#define FARROW
#include <complex.h>
namespace SPUC {











template <class Numeric> class farrow
{
 public: 
  long num_taps;
  Numeric* coeff;
 protected:
  Numeric* z; 
  Numeric output;
      
 public: 
  Numeric out() { return(output); }
  Numeric check(long i) { return(z[i]); }       
  farrow(char order) : num_taps(order) {
        int i;
        coeff = new Numeric[num_taps+1];
        z = new Numeric[num_taps+2];
        for (i=0;i<=num_taps;i++) {
          z[i] = 0;
          coeff[i] = 0;  
        }
  } 
  void reset(void) {    
          int i;
          for (i=0;i<=num_taps;i++) z[i] = 0;
          output = 0;
  }
  ~farrow(void) { 
                  delete [] coeff;
                  delete [] z;
  }
  void input(Numeric in) {
        int i; 
        for (i=num_taps+1;i>0;i--) z[i] = z[i-1];  
        z[0] = in;   
  }

  Numeric update(Numeric in, double offset) {
        int i; 
        for (i=num_taps+1;i>0;i--) z[i] = z[i-1];  
        z[0] = in;   
        if (num_taps == 1) return(in);
        else if (num_taps == 2) calculate_coeff2();
        else if (num_taps == 3) calculate_coeff3();
        else if (num_taps == 4) calculate_coeff4();
        return(fir(offset));
}
Numeric fir(double offset) {
        double gain = offset;
        output = coeff[0];
        for (int i=1;i<num_taps;i++) {
          output += offset*coeff[i];
          offset *= gain;
        }
        return(output);
}
Numeric rephase(double offset) {  
  if (num_taps == 1) return(z[0]);
  else if (num_taps == 2) calculate_coeff2();
  else if (num_taps == 3) calculate_coeff3();
  else if (num_taps == 4) calculate_coeff4();
  return(fir(offset));
}
void calculate_coeff2(void) {
        coeff[1] = z[0] - z[1];
        coeff[0] = z[1];
}
void calculate_coeff3(void) {
        coeff[2] = z[0] - 2*z[1] + z[2];
        coeff[1] = z[0] - z[2];
        coeff[0] = ((Numeric)2)*z[1];
}
void calculate_coeff3a(void) {
        coeff[2] = (z[0] - z[1] - z[2] + z[3]);
        coeff[1] = -z[0] + ((Numeric)3)*z[1] - z[2] - z[3];
        coeff[0] = ((Numeric)2)*z[2];
}
void calculate_coeff4(void) {
        coeff[3] = -z[3] + ((Numeric)3)*z[2] - ((Numeric)3)*z[1] + z[0]; 
        coeff[2] = ((Numeric)3)*z[3] - ((Numeric)6)*z[2] + ((Numeric)3)*z[1]; 
        coeff[1] = ((Numeric)-2)*z[3] - ((Numeric)3)*z[2] + ((Numeric)6)*z[1] - z[0];   
        coeff[0] = ((Numeric)6)*z[2];
}
};    
} 
#endif      

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