subroutine q65_sync(nutc,iwave,nmax,mode_q65,codewords,ncw,nsps,nfqso,ntol, & ndepth,lclearave,emedelay,xdt,f0,snr1,width,dat4,snr2,id1) ! Detect and align with the Q65 sync vector, returning time and frequency ! offsets and SNR estimate. ! Input: iwave(0:nmax-1) Raw data ! mode_q65 Tone spacing 1 2 4 8 16 (A-E) ! nsps Samples per symbol at 12000 Sa/s ! nfqso Target frequency (Hz) ! ntol Search range around nfqso (Hz) ! Output: xdt Time offset from nominal (s) ! f0 Frequency of sync tone ! snr1 Relative SNR of sync signal use packjt77 parameter (NSTEP=8) !Step size nsps/NSTEP parameter (LN=2176*63) !LN=LL*NN; LL=64*(mode_q65+2), NN=63 parameter (PLOG_MIN=-240.0) !List decoding threshold integer*2 iwave(0:nmax-1) !Raw data integer isync(22) !Indices of sync symbols integer itone(85) integer codewords(63,206) integer dat4(13) integer ijpk(2) logical unpk77_success logical lavg,lclearave character*77 c77,decoded*37 real, allocatable :: s1(:,:) !Symbol spectra, 1/8-symbol steps real, allocatable :: s3(:,:) !Data-symbol energies s3(LL,63) real, allocatable,save :: s3avg(:,:) !Averaged data-symbol energies real, allocatable :: ccf(:,:) !CCF(freq,lag) real, allocatable :: ccf1(:) !CCF(freq) at best lag real s3prob(0:63,63) !Symbol-value probabilities real sync(85) !sync vector complex, allocatable :: c0(:) !Complex spectrum of symbol data isync/1,9,12,13,15,22,23,26,27,33,35,38,46,50,55,60,62,66,69,74,76,85/ data sync(1)/99.0/,LL0/-1/ save sync,navg,LL0 snr1=0. id1=0 dat4=0 LL=64*(2+mode_q65) nfft=nsps df=12000.0/nfft !Freq resolution = baud istep=nsps/NSTEP iz=5000.0/df !Uppermost frequency bin, at 5000 Hz txt=85.0*nsps/12000.0 jz=(txt+1.0)*12000.0/istep !Number of quarter-symbol steps if(nsps.ge.6912) jz=(txt+2.0)*12000.0/istep !For TR 60 s and higher ia=ntol/df ia2=max(ia,10*mode_q65) nsmo=int(0.7*mode_q65*mode_q65) if(nsmo.lt.1) nsmo=1 allocate(s1(iz,jz)) allocate(s3(-64:LL-65,63)) if(LL.ne.LL0) then if(allocated(s3avg)) deallocate(s3avg) allocate(s3avg(-64:LL-65,63)) navg=0 LL0=LL endif allocate(c0(0:nfft-1)) allocate(ccf(-ia2:ia2,-53:214)) allocate(ccf1(-ia2:ia2)) if(lclearave) then s3avg=0. navg=0 endif if(sync(1).eq.99.0) then !Generate the sync vector sync=-22.0/63.0 !Sync tone OFF do k=1,22 sync(isync(k))=1.0 !Sync tone ON enddo endif fac=1/32767.0 do j=1,jz !Compute symbol spectra at step size i1=(j-1)*istep i2=i1+nsps-1 k=-1 do i=i1,i2,2 !Load iwave data into complex array c0, for r2c FFT xx=iwave(i) yy=iwave(i+1) k=k+1 c0(k)=fac*cmplx(xx,yy) enddo c0(k+1:)=0. call four2a(c0,nfft,1,-1,0) !r2c FFT do i=1,iz s1(i,j)=real(c0(i))**2 + aimag(c0(i))**2 enddo ! For large Doppler spreads, should we smooth the spectra here? do i=1,nsmo call smo121(s1(1:iz,j),iz) enddo enddo i0=nint(nfqso/df) !Target QSO frequency if(i0-64.lt.1 .or. i0-65+LL.gt.iz) go to 900 call pctile(s1(i0-64:i0-65+LL,1:jz),LL*jz,40,base) s1=s1/base ! Apply fast AGC s1max=20.0 !Empirical choice do j=1,jz !### Maybe wrong way? ### smax=maxval(s1(i0-64:i0-65+LL,j)) if(smax.gt.s1max) s1(i0-64:i0-65+LL,j)=s1(i0-64:i0-65+LL,j)*s1max/smax enddo dtstep=nsps/(NSTEP*12000.0) !Step size in seconds lag1=-1.0/dtstep lag2=1.0/dtstep + 0.9999 if(nsps.ge.3600 .and. emedelay.gt.0) lag2=4.0/dtstep + 0.9999 !Include EME j0=0.5/dtstep if(nsps.ge.7200) j0=1.0/dtstep !Nominal start-signal index if(ncw.lt.1) go to 100 !###################################################################### ! Try list decoding via "Deep Likelihood". ipk=0 jpk=0 ccf_best=0. imsg_best=-1 do imsg=1,ncw i=1 k=0 do j=1,85 if(j.eq.isync(i)) then i=i+1 itone(j)=-1 else k=k+1 itone(j)=codewords(k,imsg) endif enddo ! Compute 2D ccf using all 85 symbols in the list message ccf=0. do lag=lag1,lag2 do k=1,85 j=j0 + NSTEP*(k-1) + 1 + lag if(j.ge.1 .and. j.le.jz) then do i=-ia2,ia2 ii=i0+mode_q65*(itone(k)+1)+i if(ii.ge.1 .and. ii.le.iz) ccf(i,lag)=ccf(i,lag) + s1(ii,j) enddo endif enddo enddo ccfmax=maxval(ccf(-ia:ia,:)) if(ccfmax.gt.ccf_best) then ccf_best=ccfmax ijpk=maxloc(ccf(-ia:ia,:)) ipk=ijpk(1)-ia-1 jpk=ijpk(2)-53-1 f0=nfqso + ipk*df xdt=jpk*dtstep imsg_best=imsg ccf1=ccf(:,jpk) endif enddo ! imsg i1=i0+ipk-64 i2=i1+LL-1 j=j0+jpk-7 n=0 do k=1,85 j=j+8 if(sync(k).gt.0.0) then cycle endif n=n+1 if(j.ge.1 .and. j.le.jz) s3(-64:LL-65,n)=s1(i1:i2,j) enddo nsubmode=0 if(mode_q65.eq.2) nsubmode=1 if(mode_q65.eq.4) nsubmode=2 if(mode_q65.eq.8) nsubmode=3 if(mode_q65.eq.16) nsubmode=4 nFadingModel=1 baud=12000.0/nsps ibwa=1.8*log(baud*mode_q65) + 2 ibwb=min(10,ibwa+4) lavg=.false. 10 do ibw=ibwa,ibwb b90=1.72**ibw call q65_intrinsics_ff(s3,nsubmode,b90/baud,nFadingModel,s3prob) call q65_dec_fullaplist(s3,s3prob,codewords,ncw,esnodb,dat4,plog,irc) if(irc.ge.0 .and. plog.ge.PLOG_MIN) then snr2=esnodb - db(2500.0/baud) + 3.0 !Empirical adjustment id1=1 write(c77,1000) dat4(1:12),dat4(13)/2 1000 format(12b6.6,b5.5) call unpack77(c77,0,decoded,unpk77_success) !Unpack to get msgsent ! open(55,file='fort.55',status='unknown',position='append') ! write(55,3055) nutc,ibw,xdt,f0,85.0*base,ccfmax,snr2,plog, & ! irc,trim(decoded) !3055 format(i6,i3,6f8.2,i5,2x,a) ! close(55) ic=ia2/4; base=(sum(ccf1(-ia2:-ia2+ic)) + sum(ccf1(ia2-ic:ia2)))/(2.0+2.0*ic); ccf1=ccf1-base smax=maxval(ccf1) if(smax.gt.10.0) ccf1=10.0*ccf1/smax go to 200 endif enddo if(lavg) go to 900 !###################################################################### ! Establish xdt, f0, and snr1 using sync symbols (and perhaps some AP symbols) 100 ccf=0. irc=-2 dat4=0 do lag=lag1,lag2 do k=1,85 n=NSTEP*(k-1) + 1 j=n+lag+j0 if(j.ge.1 .and. j.le.jz) then do i=-ia2,ia2 if(i0+i.lt.1 .or. i0+i.gt.iz) cycle ccf(i,lag)=ccf(i,lag) + sync(k)*s1(i0+i,j) enddo endif enddo enddo ijpk=maxloc(ccf(-ia:ia,:)) ipk=ijpk(1)-ia-1 jpk=ijpk(2)-53-1 f0=nfqso + ipk*df xdt=jpk*dtstep sq=0. nsq=0 jd=(lag2-lag1)/4 do i=-ia2,ia2 do j=lag1,lag2 if(abs(j-jpk).gt.jd .and. abs(i-ipk).gt.ia/2) then sq=sq + ccf(i,j)**2 nsq=nsq+1 endif enddo enddo rms=sqrt(sq/nsq) smax=ccf(ipk,jpk) snr1=smax/rms ccf1=ccf(:,jpk)/rms if(snr1.gt.10.0) ccf1=(10.0/snr1)*ccf1 200 smax=maxval(ccf1) if(lavg) id1=10+navg !This is an average decode i1=-9999 i2=-9999 do i=-ia,ia if(i1.eq.-9999 .and. ccf1(i).ge.0.5*smax) i1=i if(i2.eq.-9999 .and. ccf1(-i).ge.0.5*smax) i2=-i enddo do i=-ia2,ia2 freq=nfqso + i*df write(17,1100) freq,ccf1(i),xdt 1100 format(3f10.3) enddo close(17) width=df*(i2-i1) if(id1.ge.1) then navg=0 s3avg=0. if(lavg) go to 900 elseif(iand(ndepth,16).eq.16) then s3avg=s3avg+s3 navg=navg+1 write(71,3071) nutc,navg,xdt,f0,snr1 3071 format(2i5,3f10.2) if(navg.ge.2) then s3=s3avg/navg lavg=.true. go to 10 endif endif 900 return end subroutine q65_sync