subroutine sync64(dd,nf1,nf2,nfqso,ntol,maxf1,dtx,f0,jpk,kpk,snrdb,c0) parameter (NMAX=60*12000) !Max size of raw data at 12000 Hz parameter (NSPS=2304) !Samples per symbol at 4000 Hz parameter (NSPC=7*NSPS) !Samples per Costas array real dd(NMAX) !Raw data real s1(0:NSPC-1) !Power spectrum of Costas 1 real s2(0:NSPC-1) !Power spectrum of Costas 2 real s3(0:NSPC-1) !Power spectrum of Costas 3 real s0(0:NSPC-1) !Sum of s1+s2+s3 real s0a(0:NSPC-1) !Best synchromized spectrum integer icos7(0:6) !Costas 7x7 tones integer ipk0(1) complex cc(0:NSPC-1) !Costas waveform complex c0(0:360000) !Complex spectrum of dd() complex c1(0:NSPC-1) !Complex spectrum of Costas 1 complex c2(0:NSPC-1) !Complex spectrum of Costas 2 complex c3(0:NSPC-1) !Complex spectrum of Costas 3 logical first data icos7/2,5,6,0,4,1,3/ !Costas 7x7 tone pattern data first/.true./ save if(first) then twopi=8.0*atan(1.0) dfgen=12000.0/6912.0 k=-1 phi=0. do j=0,6 !Compute complex Costas waveform dphi=twopi*icos7(j)*dfgen/4000.0 do i=1,2304 phi=phi + dphi if(phi.gt.twopi) phi=phi-twopi k=k+1 cc(k)=cmplx(cos(phi),sin(phi)) enddo enddo first=.false. endif npts0=54*12000 nfft1=672000 nfft2=nfft1/3 df1=12000.0/nfft1 fac=2.0/nfft1 do i=0,nfft1/2 c0(i)=fac*cmplx(dd(1+2*i),dd(2+2*i)) enddo call four2a(c0,nfft1,1,-1,0) !Forward r2c FFT call four2a(c0,nfft2,1,1,1) !Inverse c2c FFT; c0 is analytic sig npts2=npts0/3 !Downsampled complex data length nfft3=NSPC nh3=nfft3/2 df3=4000.0/nfft3 fa=max(nf1,nfqso-ntol) fb=min(nf2,nfqso+ntol) ia=max(maxf1,nint(fa/df3)) ib=min(NSPC-1-maxf1,nint(fb/df3)) iz=ib-ia+1 snr=0. jpk=0 ja=0 jb=6*4000 jstep=200 ka=-maxf1 kb=maxf1 ipk=0 kpk=0 do iter=1,2 do j1=ja,jb,jstep j2=j1 + 39*2304 j3=j1 + 77*2304 c1=1.e-4*c0(j1:j1+NSPC-1) * conjg(cc) call four2a(c1,nfft3,1,-1,1) c2=1.e-4*c0(j2:j2+NSPC-1) * conjg(cc) call four2a(c2,nfft3,1,-1,1) c3=1.e-4*c0(j3:j3+NSPC-1) * conjg(cc) call four2a(c3,nfft3,1,-1,1) s0=0. s1=0. s2=0. s3=0. do i=ia,ib freq=i*df3 s1(i)=real(c1(i))**2 + aimag(c1(i))**2 s2(i)=real(c2(i))**2 + aimag(c2(i))**2 s3(i)=real(c3(i))**2 + aimag(c3(i))**2 enddo do k=ka,kb s0(ia:ib)=s1(ia-k:ib-k) + s2(ia:ib) + s3(ia+k:ib+k) call smo121(s0(ia:ib),iz) call averms(s0(ia:ib),iz,14,ave,rms) s=(maxval(s0(ia:ib))-ave)/rms if(s.gt.snr) then jpk=j1 ! s0a=(s0-ave)/rms s0a=s0/rms snr=s dtx=jpk/4000.0 - 1.0 ipk0=maxloc(s0(ia:ib)) ipk=ipk0(1) f0=(ipk+ia-1)*df3 kpk=k endif enddo enddo ja=max(0,jpk-2*jstep) jb=min(336000-NSPC,jpk+2*jstep) jstep=10 enddo write(17) ia,ib,s0a(ia:ib) !Save data for red curve close(17) snrdb=10.0*log10(snr)-39.0 return end subroutine sync64