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154 lines
3.4 KiB
Fortran
154 lines
3.4 KiB
Fortran
subroutine sfox_sync(iwave,fsample,isync,f,t,fwidth)
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use sfox_mod
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parameter (NSTEP=8)
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integer*2 iwave(0:NMAX-1)
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integer isync(44)
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integer ipeak(2)
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integer ipeak2(1)
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complex, allocatable :: c(:) !Work array
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real, allocatable :: s(:,:) !Symbol spectra, stepped by NSTEP
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real, allocatable :: savg(:) !Average spectrum
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real, allocatable :: ccf(:,:)
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real, allocatable :: s2(:) !Fine spectrum of sync tone
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nfft=nsps
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nh=nfft/2
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istep=NSPS/NSTEP
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jz=(13.5*fsample)/istep
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df=fsample/nfft
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dtstep=istep/fsample
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fsync=1500.0-bw/2
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ftol=50.0
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ia=nint((fsync-ftol)/df)
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ib=nint((fsync+ftol)/df)
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lagmax=1.5/dtstep
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lag1=-lagmax
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lag2=lagmax
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allocate(s(0:nh/2,jz))
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allocate(savg(0:nh/2))
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allocate(c(0:nfft-1))
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allocate(ccf(ia:ib,lag1:lag2))
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s=0.
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savg=0.
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fac=1.0/nfft
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! Compute symbol spectra with df=baud/2 and NSTEP steps per symbol.
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do j=1,jz
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i1=(j-1)*istep
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i2=i1+nsps-1
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k=-1
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do i=i1,i2,2 !Load iwave data into complex array c0, for r2c FFT
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xx=iwave(i)
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yy=iwave(i+1)
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k=k+1
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c(k)=fac*cmplx(xx,yy)
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enddo
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c(k+1:)=0.
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call four2a(c,nfft,1,-1,0) !r2c FFT
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do i=1,nh/2
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s(i,j)=real(c(i))**2 + aimag(c(i))**2
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savg(i)=savg(i) + s(i,j)
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enddo
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enddo
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savg=savg/jz
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ccfbest=0.
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ibest=0
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lagpk=0
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lagbest=0
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j0=0.5/dtstep !Nominal start-signal index
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do i=ia,ib
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ccfmax=0.
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do lag=lag1,lag2
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ccft=0.
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do m=1,NS
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k=isync(m)
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n=NSTEP*(k-1) + 1
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j=n+lag+j0
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if(j.ge.1 .and. j.le.jz) ccft=ccft + s(i,j)
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enddo ! m
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ccft=ccft - NS*savg(i)
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ccf(i,lag)=ccft
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if(ccft.gt.ccfmax) then
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ccfmax=ccft
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lagpk=lag
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endif
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enddo ! lag
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if(ccfmax.gt.ccfbest) then
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ccfbest=ccfmax
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ibest=i
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lagbest=lagpk
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endif
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enddo ! i
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ipeak=maxloc(ccf)
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ipk=ipeak(1)-1+ia
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jpk=ipeak(2)-1+lag1
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dxj=0.
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if(jpk.gt.lag1 .and. jpk.lt.lag2) then
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call peakup(ccf(ipk,jpk-1),ccf(ipk,jpk),ccf(ipk,jpk+1),dxj)
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endif
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f=ibest*df + bw/2 + dxi*df
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t=(lagbest+dxj)*dtstep
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t=t-0.01 !### Why is this needed? ###
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nfft2=4*NSPS
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deallocate(c)
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allocate(c(0:nfft2-1))
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allocate(s2(0:nfft2-1))
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i0=(t+0.5)*fsample
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s2=0.
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df2=fsample/nfft2
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do m=1,NS
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i1=i0+(isync(m)-1)*NSPS
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i2=i1+NSPS-1
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k=-1
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do i=i1,i2,2 !Load iwave data into complex array c0, for r2c FFT
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if(i.gt.0) then
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xx=iwave(i)
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yy=iwave(i+1)
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else
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xx=0.
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yy=0.
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endif
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k=k+1
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c(k)=fac*cmplx(xx,yy)
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enddo
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c(k+1:)=0.
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call four2a(c,nfft2,1,-1,0) !r2c FFT
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do i=1,nfft2/4
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s2(i)=s2(i) + real(c(i))**2 + aimag(c(i))**2
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enddo
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enddo
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ia=nint((fsync-ftol)/df2)
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ib=nint((fsync+ftol)/df2)
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ipeak2=maxloc(s2(ia:ib))
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ipk=ipeak2(1)-1+ia
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dxi=0.
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if(ipk.gt.1 .and. ipk.lt.nfft/4) then
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call peakup(s2(ipk-1),s2(ipk),s2(ipk+1),dxi)
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endif
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f=(ipk+dxi)*df2 + bw/2.0
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fwidth=0.
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if(ipk.gt.100 .and. ipk.lt.nfft2/4-100) then
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call pctile(s2(ipk-100:ipk+100),201,48,base)
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s2=s2-base
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smax=maxval(s2(ipk-10:ipk+10))
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w=count(s2(ipk-10:ipk+10).gt.0.5*smax)
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if(w.gt.4.0) fwidth=sqrt(w*w - 4*4)*df2
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endif
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return
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end subroutine sfox_sync
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