Examples of DSP.filter.LagrangePolynomial

DSP.filter.LagrangePolynomial
Implements Lagrange Polynomials. This class principally supports the design of equiripple FIR digital filters with the Remez exchange algorithm (package equiripple).

      
      double delta = computeDelta( G );
      
      System.out.println( "delta: " + delta );
       
      LagrangePolynomial LP = constructInterpolatingPolynomial( G, delta );
    
      //  Compute current approximant (GA) and error function (E) on grid
    
      for ( int i = 0;  i < G.gridSize;  i++ ) {
        GA[i] = LP.evaluate( G.X[i] );
        E[i]  = GA[i] - G.H[i];
      }
      
      // Search for new extrema starting from old extrema

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      x[i] = G.X[ j ];
      f[i] = G.H[j] - s*delta/G.W[j];
      s = -s;
    }
    
    return new LagrangePolynomial( x, f );
  }

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   * @param   Nc   The number of coefficients of the corresponding FIR filter.  
   * @return       double[] containing the coefficients of the FIR filter.
   */
  static double[] calculateCoefficients( DesignGrid G, int Nc ) {
    
    LagrangePolynomial LP = constructInterpolatingPolynomial( G, computeDelta( G ) );
   
    int     log2nfft = 6;
    int     nfft     = 64;
    while ( nfft < Nc ) {
      nfft *= 2;
      log2nfft++;
    }
    double[] X        = new double[ nfft ];
    double[] x        = new double[ nfft ];
    for ( int i = 0;  i <= nfft/2;  i++ ) {
      X[i] = (double) LP.evaluate( Math.cos( 2.0*Math.PI*i/nfft ) );
    }
    
    RDFT dft = new RDFT( log2nfft );
    dft.evaluateInverse( X, x );

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Related Classes of DSP.filter.LagrangePolynomial

DSP.filter.fir.equiripple.EquirippleDesigner

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