mirror of https://github.com/saitohirga/WSJT-X.git
180 lines
4.6 KiB
Fortran
180 lines
4.6 KiB
Fortran
subroutine sync24(dat,jz,DFTolerance,NFreeze,MouseDF,mode,mode4, &
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dtx,dfx,snrx,snrsync,ccfblue,ccfred1,flip,width)
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! Synchronizes JT4 data, finding the best-fit DT and DF.
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parameter (NFFTMAX=2520) !Max length of FFTs
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parameter (NHMAX=NFFTMAX/2) !Max length of power spectra
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parameter (NSMAX=525) !Max number of half-symbol steps
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integer DFTolerance !Range of DF search
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real dat(jz)
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real psavg(NHMAX) !Average spectrum of whole record
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real s2(NHMAX,NSMAX) !2d spectrum, stepped by half-symbols
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real ccfblue(-5:540) !CCF with pseudorandom sequence
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real ccfred(-450:450) !Peak of ccfblue, as function of freq
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real ccfred1(-224:224) !Peak of ccfblue, as function of freq
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real tmp(1260)
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save
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! Do FFTs of twice symbol length, stepped by half symbols. Note that
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! we have already downsampled the data by factor of 2.
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nsym=207
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nfft=2520
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nh=nfft/2
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nq=nfft/4
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nsteps=jz/nq - 1
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df=0.5*11025.0/nfft
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psavg(1:nh)=0.
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do j=1,nsteps !Compute spectrum for each step, get average
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k=(j-1)*nq + 1
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call ps24(dat(k),nfft,s2(1,j))
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psavg(1:nh)=psavg(1:nh) + s2(1:nh,j)
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enddo
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call flat1(psavg,s2,nh,nsteps,NHMAX,NSMAX) !Flatten spectra
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! Set freq and lag ranges
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famin=200.
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fbmax=2700.
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fa=famin
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fb=fbmax
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if(NFreeze.eq.1) then
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fa=max(famin,1270.46+MouseDF-DFTolerance)
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fb=min(fbmax,1270.46+MouseDF+DFTolerance)
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else
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fa=max(famin,1270.46+MouseDF-600)
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fb=min(fbmax,1270.46+MouseDF+600)
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endif
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ia=fa/df
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ib=fb/df
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if(mode.eq.7) then
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ia=ia - 3*mode4
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ib=ib - 3*mode4
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endif
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i0=nint(1270.46/df)
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lag1=-5
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lag2=59
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syncbest=-1.e30
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syncbest2=-1.e30
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ccfred=0.
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do i=ia,ib !Find best frequency channel for CCF
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call xcor24(s2,i,nsteps,nsym,lag1,lag2,mode4,ccfblue,ccf0,lagpk0,flip)
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j=i-i0
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if(mode.eq.7) j=j + 3*mode4
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if(j.ge.-372 .and. j.le.372) ccfred(j)=ccf0
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! Find rms of the CCF, without main peak
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call slope(ccfblue(lag1),lag2-lag1+1,lagpk0-lag1+1.0)
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sync=abs(ccfblue(lagpk0))
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ppmax=psavg(i)-1.0
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! Find best sync value
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if(sync.gt.syncbest2) then
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ipk2=i
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lagpk2=lagpk0
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syncbest2=sync
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endif
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! We are most interested if snrx will be more than -30 dB.
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if(ppmax.gt.0.2938) then !Corresponds to snrx.gt.-30.0
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if(sync.gt.syncbest) then
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ipk=i
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lagpk=lagpk0
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syncbest=sync
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endif
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endif
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enddo
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! If we found nothing with snrx > -30 dB, take the best sync that *was* found.
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if(syncbest.lt.-10.) then
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ipk=ipk2
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lagpk=lagpk2
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syncbest=syncbest2
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endif
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dfx=(ipk-i0)*df
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if(mode.eq.7) dfx=dfx + 3*mode4*df
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! Peak up in time, at best whole-channel frequency
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call xcor24(s2,ipk,nsteps,nsym,lag1,lag2,mode4,ccfblue,ccfmax,lagpk,flip)
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xlag=lagpk
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if(lagpk.gt.lag1 .and. lagpk.lt.lag2) then
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call peakup(ccfblue(lagpk-1),ccfmax,ccfblue(lagpk+1),dx2)
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xlag=lagpk+dx2
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endif
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! Find rms of the CCF, without the main peak
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call slope(ccfblue(lag1),lag2-lag1+1,xlag-lag1+1.0)
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sq=0.
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nsq=0
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do lag=lag1,lag2
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if(abs(lag-xlag).gt.2.0) then
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sq=sq+ccfblue(lag)**2
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nsq=nsq+1
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endif
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enddo
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rms=sqrt(sq/nsq)
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snrsync=abs(ccfblue(lagpk))/rms - 1.1 !Empirical
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dt=2.0/11025.0
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istart=xlag*nq
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dtx=istart*dt
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snrx=-99.0
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ppmax=psavg(ipk)-1.0
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if(ppmax.gt.0.0001) then
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snrx=db(ppmax*df/2500.0) + 7.5 !Empirical
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if(mode.eq.7) snrx=snrx + 3.0 !Empirical
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endif
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if(snrx.lt.-33.0) snrx=-33.0
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! Compute width of sync tone to outermost -3 dB points
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i1=max(-450,ia-i0)
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i2=min(450,ib-i0)
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call pctile(ccfred(i1),i2-i1+1,45,base)
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jpk=ipk-i0
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if(abs(jpk).gt.450) then
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print*,'sync24 a:',jpk,ipk,i0
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snrsync=0.
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go to 999
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else
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stest=base + 0.5*(ccfred(jpk)-base) ! -3 dB
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endif
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do i=-10,0
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if(jpk+i.ge.-371) then
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if(ccfred(jpk+i).gt.stest) go to 30
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endif
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enddo
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i=0
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30 continue
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if(abs(jpk+i-1).gt.450 .or. abs(jpk+i).gt.450) then
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print*,'sync24 b:',jpk,i
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else
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x1=i-0.5
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endif
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do i=10,0,-1
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if(jpk+i.le.371) then
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if(ccfred(jpk+i).gt.stest) go to 32
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endif
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enddo
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i=0
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32 x2=i+0.5
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width=x2-x1
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if(width.gt.1.2) width=sqrt(width**2 - 1.44)
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width=df*width
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width=max(0.0,min(99.0,width))
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do i=-224,224
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ccfred1(i)=ccfred(i)
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enddo
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999 return
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end subroutine sync24
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