mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-05 08:51:19 -05:00
7ff366abe3
NB: should remove the present downsampling to 11025/2 Hz, which unnecessarily
limits the availabler range of Fx Freq ("nfqso" in the source code).
147 lines
3.9 KiB
Fortran
147 lines
3.9 KiB
Fortran
subroutine sync4(dat,jz,ntol,nfqso,mode,mode4,minwidth,dtx,dfx,snrx, &
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snrsync,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 ntol !Range of DF search
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real dat(jz)
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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(NHMAX) !Peak of ccfblue, as function of freq
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real red(NHMAX) !Peak of ccfblue, as function of freq
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integer ipk1(1)
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integer nch(7)
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logical savered
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equivalence (ipk1,ipk1a)
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data nch/1,2,4,9,18,36,72/
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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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ftop=nfqso + 7*mode4*df
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if(ftop.gt.11025.0/4.0) then
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print*,'*** Rx Freq is set too high for this sybmode ***'
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go to 900
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endif
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if(mode.eq.-999) width=0. !Silence compiler warning
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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 ps4(dat(k),nfft,s2(1,j))
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enddo
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! Set freq and lag ranges
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ia=(nfqso-ntol)/df !Index of lowest tone, bottom of search range
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ib=(nfqso+ntol)/df !Index of lowest tone, top of search range
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iamin=nint(100.0/df)
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if(ia.lt.iamin) ia=iamin
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ibmax=nint(2700.0/df) - 6*mode4
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if(ib.gt.ibmax) ib=ibmax
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lag1=-5
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lag2=59
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syncbest=-1.e30
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snrx=-26.0
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ccfred=0.
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red=0.
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i0=nint(nfqso/df)
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do ich=minwidth,7 !Find best width
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kz=nch(ich)/2
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savered=.false.
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iaa=ia+kz
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ibb=ib-kz
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do i=iaa,ibb !Find best frequency channel for CCF
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call xcor4(s2,i,nsteps,nsym,lag1,lag2,ich,mode4,ccfblue,ccf0, &
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lagpk0,flip)
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ccfred(i)=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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! write(*,3000) ich,i,i*df,ccf0,sync,syncbest
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!3000 format(2i5,4f12.3)
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! Find best sync value
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if(sync.gt.syncbest*1.03) then
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ipk=i
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lagpk=lagpk0
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ichpk=ich
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syncbest=sync
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savered=.true.
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endif
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enddo
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if(savered) red=ccfred
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enddo
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if(syncbest.lt.-1.e29) go to 900
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ccfred=red
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call pctile(ccfred(iaa:ibb),ibb-iaa+1,45,base)
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ccfred=ccfred-base
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dfx=ipk*df
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! Peak up in time, at best whole-channel frequency
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call xcor4(s2,ipk,nsteps,nsym,lag1,lag2,ichpk,mode4,ccfblue,ccfmax, &
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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=max(0.0,db(abs(ccfblue(lagpk)/rms - 1.0)) - 4.5)
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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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ipk1=maxloc(ccfred)
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ccf10=0.5*maxval(ccfred)
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do i=ipk1a,ia,-1
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if(ccfred(i).le.ccf10) exit
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enddo
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i1=i
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do i=ipk1a,ib
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if(ccfred(i).le.ccf10) exit
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enddo
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nw=i-i1
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width=nw*df
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sq=0.
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ns=0
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iaa=max(ipk1a-10*nw,ia)
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ibb=min(ipk1a+10*nw,ib)
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jmax=2*mode4/3
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do i=iaa,ibb
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j=abs(i-ipk1a)
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if(j.gt.nw .and. j.lt.jmax) then
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sq=sq + ccfred(j)*ccfred(j)
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ns=ns+1
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endif
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enddo
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rms=sqrt(sq/ns)
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snrx=10.0*log10(ccfred(ipk1a)/rms) - 41.2
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900 return
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end subroutine sync4
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