modulator.cpp

QPSK调制Modem的C实现及文档说明

/********************************************************************
 * modulator -- Modulates an input signal sample by sample          *
 * Functions -- CosModulation, SinModulation                        *
 * Inputs -- Sample to be modulated                                 *
 * Returns -- Corresponding modulated sample                        *
 ********************************************************************/
 
class modulator {
   private:
     double CosCarrier[4];				/* 4 samples per period */
     double SinCarrier[4];
     long int counter1,counter2;


	public:
      modulator()
      { CosCarrier[0]=cos(0);
        SinCarrier[0]=sin(0);
        CosCarrier[1]=cos(M_PI/2);
        SinCarrier[1]=sin(M_PI/2);
        CosCarrier[2]=cos(M_PI);
        SinCarrier[2]=sin(M_PI);
        CosCarrier[3]=cos(3*M_PI/2);
        SinCarrier[3]=sin(3*M_PI/2);
        counter1=0;
        counter2=0;
      }

      void ShiftPhase(double PhaseShift, double SlopeOfShift)
      { CosCarrier[0]=cos(0+PhaseShift);
        SinCarrier[0]=sin(0+PhaseShift);
        CosCarrier[1]=cos(M_PI/2+PhaseShift);
        SinCarrier[1]=sin(M_PI/2+PhaseShift);
        CosCarrier[2]=cos(M_PI+PhaseShift);
        SinCarrier[2]=sin(M_PI+PhaseShift);
        CosCarrier[3]=cos(3*M_PI/2+PhaseShift);
        SinCarrier[3]=sin(3*M_PI/2+PhaseShift);
     /* PhaseShift=PhaseShift+SlopeOfShift; */
      }
		double CosModulation(double CosSample);
		double SinModulation(double SinSample);
};

double modulator :: CosModulation(double CosSample)
{ double temp;
  temp=(CosCarrier[counter1%4]*CosSample);
  ++counter1;
  return temp;
};

double modulator :: SinModulation(double SinSample)
{ double temp;
  temp=(SinCarrier[counter2%4]*SinSample);
  ++counter2;
  return temp;
};