subroutine sync_q65(iwave,nmax,mode65,nsps,nfqso,ntol,xdt,f0,snr1) ! Detect and align with the Q65 sync vector, returning time and frequency ! offsets and SNR estimate. ! Input: iwave(0:nmax-1) Raw data ! mode65 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 parameter (NSTEP=8) !Step size nsps/NSTEP integer*2 iwave(0:nmax-1) !Raw data integer isync(22) !Indices of sync symbols integer ijpk(2) !Indices i and j at peak of ccf real, allocatable :: s1(:,:) !Symbol spectra, quarter-symbol steps real sync(85) !sync vector real ccf(-64:64,-53:214) !CCF(freq,time) 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/ save sync nfft=2*nsps df=12000.0/nfft !Freq resolution = 0.5*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 allocate(s1(iz,jz)) allocate(c0(0:nfft-1)) 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 ia=(j-1)*istep ib=ia+nsps-1 k=-1 do i=ia,ib,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? call smo121(s1(1:iz,j),iz) enddo i0=nint(nfqso/df) !Target QSO frequency call pctile(s1(i0-64:i0+192,1:jz),129*jz,40,base) s1=s1/base - 1.0 ! Apply fast AGC s1max=20.0 !Empirical choice do j=1,jz smax=maxval(s1(i0-64:i0+192,j)) if(smax.gt.s1max) s1(i0-64:i0+192,j)=s1(i0-64:i0+192,j)*s1max/smax enddo dtstep=nsps/(NSTEP*12000.0) !Step size in seconds j0=0.5/dtstep if(nsps.ge.6192) j0=1.0/dtstep !Nominal index for start of signal ccf=0. ia=min(64,nint(ntol/df)) lag1=-1.0/dtstep lag2=4.0/dtstep + 0.9999 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 ccf(-ia:ia,lag)=ccf(-ia:ia,lag) + sync(k)*s1(i0-ia:i0+ia,j) endif enddo enddo ijpk=maxloc(ccf) ipk=ijpk(1)-65 jpk=ijpk(2)-54 f0=nfqso + ipk*df xdt=jpk*dtstep sq=0. nsq=0 do j=lag1,lag2 if(abs(j-jpk).gt.6) then sq=sq + ccf(ipk,j)**2 nsq=nsq+1 endif enddo rms=sqrt(sq/nsq) smax=ccf(ipk,jpk) snr1=smax/rms ! do j=lag1,lag2 ! write(55,3055) j,j*dtstep,ccf(ipk,j)/rms !3055 format(i5,f8.3,f10.3) ! enddo ! do i=-ia,ia ! write(56,3056) i*df,ccf(i,0)/rms !3056 format(2f10.3) ! enddo return end subroutine sync_q65