subroutine sync4(dat,jz,ntol,nfqso,mode,mode4,minwidth,dtx,dfx,snrx, & snrsync,flip,width) ! Synchronizes JT4 data, finding the best-fit DT and DF. parameter (NFFTMAX=2520) !Max length of FFTs parameter (NHMAX=NFFTMAX/2) !Max length of power spectra parameter (NSMAX=525) !Max number of half-symbol steps integer ntol !Range of DF search real dat(jz) real s2(NHMAX,NSMAX) !2d spectrum, stepped by half-symbols real ccfblue(-5:540) !CCF with pseudorandom sequence real ccfred(NHMAX) !Peak of ccfblue, as function of freq real red(NHMAX) !Peak of ccfblue, as function of freq integer ipk1(1) integer nch(7) logical savered equivalence (ipk1,ipk1a) data nch/1,2,4,9,18,36,72/ save ! Do FFTs of twice symbol length, stepped by half symbols. Note that ! we have already downsampled the data by factor of 2. nsym=207 nfft=2520 nh=nfft/2 nq=nfft/4 nsteps=jz/nq - 1 df=0.5*11025.0/nfft ftop=nfqso + 7*mode4*df if(ftop.gt.11025.0/4.0) then print*,'*** Rx Freq is set too high for this sybmode ***' go to 900 endif if(mode.eq.-999) width=0. !Silence compiler warning do j=1,nsteps !Compute spectrum for each step, get average k=(j-1)*nq + 1 call ps4(dat(k),nfft,s2(1,j)) enddo ! Set freq and lag ranges ia=(nfqso-ntol)/df !Index of lowest tone, bottom of search range ib=(nfqso+ntol)/df !Index of lowest tone, top of search range iamin=nint(100.0/df) if(ia.lt.iamin) ia=iamin ibmax=nint(2700.0/df) - 6*mode4 if(ib.gt.ibmax) ib=ibmax lag1=-5 lag2=59 syncbest=-1.e30 snrx=-26.0 ccfred=0. red=0. i0=nint(nfqso/df) do ich=minwidth,7 !Find best width kz=nch(ich)/2 savered=.false. iaa=ia+kz ibb=ib-kz do i=iaa,ibb !Find best frequency channel for CCF call xcor4(s2,i,nsteps,nsym,lag1,lag2,ich,mode4,ccfblue,ccf0, & lagpk0,flip) ccfred(i)=ccf0 ! Find rms of the CCF, without main peak call slope(ccfblue(lag1),lag2-lag1+1,lagpk0-lag1+1.0) sync=abs(ccfblue(lagpk0)) ! write(*,3000) ich,i,i*df,ccf0,sync,syncbest !3000 format(2i5,4f12.3) ! Find best sync value if(sync.gt.syncbest*1.03) then ipk=i lagpk=lagpk0 ichpk=ich syncbest=sync savered=.true. endif enddo if(savered) red=ccfred enddo if(syncbest.lt.-1.e29) go to 900 ccfred=red call pctile(ccfred(iaa:ibb),ibb-iaa+1,45,base) ccfred=ccfred-base dfx=ipk*df ! Peak up in time, at best whole-channel frequency call xcor4(s2,ipk,nsteps,nsym,lag1,lag2,ichpk,mode4,ccfblue,ccfmax, & lagpk,flip) xlag=lagpk if(lagpk.gt.lag1 .and. lagpk.lt.lag2) then call peakup(ccfblue(lagpk-1),ccfmax,ccfblue(lagpk+1),dx2) xlag=lagpk+dx2 endif ! Find rms of the CCF, without the main peak call slope(ccfblue(lag1),lag2-lag1+1,xlag-lag1+1.0) sq=0. nsq=0 do lag=lag1,lag2 if(abs(lag-xlag).gt.2.0) then sq=sq+ccfblue(lag)**2 nsq=nsq+1 endif enddo rms=sqrt(sq/nsq) snrsync=max(0.0,db(abs(ccfblue(lagpk)/rms - 1.0)) - 4.5) dt=2.0/11025.0 istart=xlag*nq dtx=istart*dt ipk1=maxloc(ccfred) ccf10=0.5*maxval(ccfred) do i=ipk1a,ia,-1 if(ccfred(i).le.ccf10) exit enddo i1=i do i=ipk1a,ib if(ccfred(i).le.ccf10) exit enddo nw=i-i1 width=nw*df sq=0. ns=0 iaa=max(ipk1a-10*nw,ia) ibb=min(ipk1a+10*nw,ib) jmax=2*mode4/3 do i=iaa,ibb j=abs(i-ipk1a) if(j.gt.nw .and. j.lt.jmax) then sq=sq + ccfred(j)*ccfred(j) ns=ns+1 endif enddo rms=sqrt(sq/ns) snrx=10.0*log10(ccfred(ipk1a)/rms) - 41.2 900 return end subroutine sync4