mirror of https://github.com/saitohirga/WSJT-X.git
69 lines
1.7 KiB
Fortran
69 lines
1.7 KiB
Fortran
real function fchisq65(cx,npts,fsample,nflip,a,ccfmax,dtmax)
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use timer_module, only: timer
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parameter (NMAX=60*12000) !Samples per 60 s
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complex cx(npts)
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real a(5)
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complex w,wstep,z
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real ss(3000)
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complex csx(0:NMAX/8)
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data twopi/6.283185307/a1,a2,a3/99.,99.,99./
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save
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call timer('fchisq65',0)
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baud=11025.0/4096.0
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nsps=nint(fsample/baud) !Samples per symbol
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nsph=nsps/2 !Samples per half-symbol
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ndiv=16 !Output ss() steps per symbol
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nout=ndiv*npts/nsps
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dtstep=1.0/(ndiv*baud) !Time per output step
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if(a(1).ne.a1 .or. a(2).ne.a2 .or. a(3).ne.a3) then
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a1=a(1)
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a2=a(2)
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a3=a(3)
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! Mix and integrate the complex signal
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csx(0)=0.
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w=1.0
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x0=0.5*(npts+1)
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s=2.0/npts
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do i=1,npts
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x=s*(i-x0)
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if(mod(i,100).eq.1) then
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p2=1.5*x*x - 0.5
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dphi=(a(1) + x*a(2) + p2*a(3)) * (twopi/fsample)
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wstep=cmplx(cos(dphi),sin(dphi))
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endif
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w=w*wstep
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csx(i)=csx(i-1) + w*cx(i)
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enddo
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endif
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! Compute whole-symbol powers at 1/16-symbol steps.
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fac=1.e-4
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do i=1,nout
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j=nsps+(i-1)*nsps/16 !steps by 8 samples (1/16 of a symbol)
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k=j-nsps
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ss(i)=0.
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if(k.ge.0 .and. j.le.npts) then
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z=csx(j)-csx(k) ! difference over span of 128 pts
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ss(i)=fac*(real(z)**2 + aimag(z)**2)
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endif
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enddo
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ccfmax=0.
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call timer('ccf2 ',0)
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call ccf2(ss,nout,nflip,ccf,xlagpk)
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call timer('ccf2 ',1)
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if(ccf.gt.ccfmax) then
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ccfmax=ccf
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dtmax=xlagpk*dtstep
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endif
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fchisq65=-ccfmax
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call timer('fchisq65',1)
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return
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end function fchisq65
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