real function fchisq(cx,cy,npts,fsample,nflip,a,ccfmax,dtmax) use timer_module, only: timer parameter (NMAX=60*96000) !Samples per 60 s complex cx(npts),cy(npts) real a(5) complex w,wstep,za,zb,z real ss(3000) complex csx(0:NMAX/64),csy(0:NMAX/64) data twopi/6.283185307/a1,a2,a3/99.,99.,99./ save call timer('fchisq ',0) baud=11025.0/4096.0 nsps=nint(fsample/baud) !Samples per symbol nsph=nsps/2 !Samples per half-symbol ndiv=16 !Output ss() steps per symbol nout=ndiv*npts/nsps dtstep=1.0/(ndiv*baud) !Time per output step if(a(1).ne.a1 .or. a(2).ne.a2 .or. a(3).ne.a3) then a1=a(1) a2=a(2) a3=a(3) ! Mix and integrate the complex X and Y signals csx(0)=0. csy(0)=0. w=1.0 x0=0.5*(npts+1) s=2.0/npts do i=1,npts x=s*(i-x0) if(mod(i,100).eq.1) then p2=1.5*x*x - 0.5 ! p3=2.5*(x**3) - 1.5*x ! p4=4.375*(x**4) - 3.75*(x**2) + 0.375 dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/fsample) wstep=cmplx(cos(dphi),sin(dphi)) endif w=w*wstep csx(i)=csx(i-1) + w*cx(i) csy(i)=csy(i-1) + w*cy(i) enddo endif ! Compute 1/2-symbol powers at 1/16-symbol steps. fac=1.e-4 pol=a(4)/57.2957795 aa=cos(pol) bb=sin(pol) do i=1,nout j=i*nsps/ndiv k=j-nsph ss(i)=0. if(k.ge.1) then za=csx(j)-csx(k) zb=csy(j)-csy(k) z=aa*za + bb*zb ss(i)=fac*(real(z)**2 + aimag(z)**2) endif enddo ccfmax=0. call timer('ccf2 ',0) call ccf2(ss,nout,nflip,ccf,lagpk) call timer('ccf2 ',1) if(ccf.gt.ccfmax) then ccfmax=ccf dtmax=lagpk*dtstep endif fchisq=-ccfmax call timer('fchisq ',1) return end function fchisq