void LOinit(){
  for(int k=0 ; k<4096 ; k++){
    DDStable[k]=2048.0*sin(twopi*k/4096.0) ;
    }
  LOphase=0 ;
  LOincrement=LOfrequency/sampleFrequency1*(double)(0x100000000L) ;
  }
  
void LOstep(){
  LOphase += LOincrement ;
  LOcos=DDStable[ (LOphase >> 20 ) & 0xFFF ] ;
  LOsin=DDStable[ ((LOphase >> 20 )+0x400) & 0xFFF ] ;
  }
