mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-03 16:01:18 -05:00
b30d2e3e8c
sync65: added call to smooth for improved sync in mode JT65C.
added +2 dB to SNR estimates for JT65C.
wsjt65: cleaned up some display details of decoded lines
short65: added calls to smooth for improved shorthand decodes in JT65C.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/trunk@217 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
172 lines
5.0 KiB
Fortran
172 lines
5.0 KiB
Fortran
subroutine sync65(dat,jz,DFTolerance,NFreeze,NAFC,MouseDF,
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+ mode65,dtx,dfx,snrx,snrsync,ccfblue,ccfred,flip,width)
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C Synchronizes JT65 data, finding the best-fit DT and DF.
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C NB: at this stage, submodes ABC are processed in the same way.
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parameter (NP2=60*11025) !Size of data array
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parameter (NFFTMAX=2048) !Max length of FFTs
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parameter (NHMAX=NFFTMAX/2) !Max length of power spectra
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parameter (NSMAX=320) !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(-224:224) !Peak of ccfblue, as function of freq
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real tmp(450)
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integer itry(100)
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save
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C Do FFTs of symbol length, stepped by half symbols. Note that we have
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C already downsampled the data by factor of 2.
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nsym=126
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nfft=2048
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nsteps=2*jz/nfft - 1
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nh=nfft/2
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df=0.5*11025.0/nfft
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C Compute power spectrum for each step and get average
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call zero(psavg,nh)
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do j=1,nsteps
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k=(j-1)*nh + 1
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call limit(dat(k),nfft)
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call ps(dat(k),nfft,s2(1,j))
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if(mode65.eq.4) call smooth(s2(1,j),nh)
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call add(psavg,s2(1,j),psavg,nh)
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enddo
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call flat1(psavg,s2,nh,nsteps,NHMAX,NSMAX) !Flatten the spectra
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C Find the best frequency channel for CCF
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fa= 670.46
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fb=1870.46
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if(NFreeze.eq.1) then
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fa=max( 670.46,1270.46+MouseDF-DFTolerance)
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fb=min(1870.46,1270.46+MouseDF+DFTolerance)
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endif
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ia=fa/df
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ib=fb/df
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i0=nint(1270.46/df)
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ired0=ia-i0
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ired1=ib-i0
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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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call zero(ccfred,449)
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do i=ia,ib
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call xcor(s2,i,nsteps,nsym,lag1,lag2,
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+ ccfblue,ccf0,lagpk0,flip,0.0)
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ccfred(i-i0)=ccf0
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C Find rms of the CCF, without the 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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C Find the 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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flippk2=flip
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endif
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C 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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flippk=flip
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endif
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endif
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enddo
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C 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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flippk=flippk2
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endif
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C Peak up in frequency to fraction of channel
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base=0.25*(psavg(ipk-3)+psavg(ipk-2)+psavg(ipk+2)+psavg(ipk+3))
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! call peakup(psavg(ipk-1),psavg(ipk),psavg(ipk+1),dx)
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! if(dx.lt.-1.0) dx=-1.0
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! if(dx.gt.1.0) dx=1.0
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dx=0.
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dfx=(ipk+dx-i0)*df
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C Peak up in time, at best whole-channel frequency
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call xcor(s2,ipk,nsteps,nsym,lag1,lag2,
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+ ccfblue,ccfmax,lagpk,flip,0.0)
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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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C 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*nh
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dtx=istart*dt
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snrx=-99.0
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! ppmax=psavg(ipk)/base-1.0
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ppmax=psavg(ipk)-1.0
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C Plus 3 dB because sync tone is on half the time. (Don't understand
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C why an additional +2 dB is needed ...)
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if(ppmax.gt.0.0001) snrx=db(ppmax*df/2500.0) + 5.0 !###
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if(mode65.eq.4) snrx=snrx + 2.0
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if(snrx.lt.-33.0) snrx=-33.0
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C Compute width of sync tone to outermost -3 dB points
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call pctile(ccfred(ia-i0),tmp,ib-ia+1,45,base)
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jpk=ipk-i0
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stest=base + 0.5*(ccfred(jpk)-base) ! -3 dB
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do i=-10,0
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if(jpk+i.ge.-223) 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 x1=i-1+(stest-ccfred(jpk+i-1))/(ccfred(jpk+i)-ccfred(jpk+i-1))
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do i=10,0,-1
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if(jpk+i.le.223) 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+1-(stest-ccfred(jpk+i+1))/(ccfred(jpk+i)-ccfred(jpk+i+1))
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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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ic=600/df
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nn=1800/df
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nred=448
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return
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end
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