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99 lines
2.3 KiB
Fortran
99 lines
2.3 KiB
Fortran
subroutine sync66(iwave,nmax,nsps,nfqso,ntol,xdt,f0,snr1)
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parameter (NSTEP=4) !Quarter-symbol steps
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parameter (IZ=1600,JZ=352,NSPSMAX=1920)
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integer*2 iwave(0:nmax-1) !Raw data
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integer b11(11) !Barker 11 code
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integer ijpk(2) !Indices i and j at peak of sync_sig
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real s1(IZ,JZ) !Symbol spectra
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real x(JZ) !Work array; 2FSK sync modulation
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real sync(4*85) !sync vector
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real sync_sig(-64:64,-15:15)
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complex c0(0:NSPSMAX) !Complex spectrum of symbol
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data b11/1,1,1,0,0,0,1,0,0,1,0/ !Barker 11 code
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data sync(1)/99.0/
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save sync
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if(sync(1).eq.99.0) then
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sync=0.
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do k=1,22
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kk=k
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if(kk.gt.11) kk=k-11
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sync(16*k-15)=2.0*b11(kk) - 1.0
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enddo
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endif
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nfft=2*NSPS
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df=12000.0/nfft !3.125 Hz
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istep=nsps/NSTEP
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fac=1/32767.0
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do j=1,JZ !Compute symbol spectra
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ia=(j-1)*istep
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ib=ia+nsps-1
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k=-1
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do i=ia,ib,2
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xx=iwave(i)
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yy=iwave(i+1)
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k=k+1
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c0(k)=fac*cmplx(xx,yy)
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enddo
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c0(k+1:nfft/2)=0.
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call four2a(c0,nfft,1,-1,0) !r2c FFT
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do i=1,IZ
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s1(i,j)=real(c0(i))**2 + aimag(c0(i))**2
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enddo
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enddo
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i0=nint(nfqso/df)
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call pctile(s1(i0-64:i0+192,1:JZ),129*JZ,40,base)
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s1=s1/base
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s1max=20.0
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! Apply AGC
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do j=1,JZ
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x(j)=maxval(s1(i0-64:i0+192,j))
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if(x(j).gt.s1max) s1(i0-64:i0+192,j)=s1(i0-64:i0+192,j)*s1max/x(j)
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enddo
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dt4=nsps/(NSTEP*12000.0)
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j0=0.5/dt4
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sync_sig=0.
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ia=min(64,nint(ntol/df))
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do i=-ia,ia
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x=s1(i0+2+i,:)-s1(i0+i,:)
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do lag=-15,15
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! Make this simpler: just add the 22 nonzero values?
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do n=1,4*85
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j=n+lag+11
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if(j.ge.1 .and. j.le.JZ) sync_sig(i,lag)=sync_sig(i,lag) + sync(n)*x(j)
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enddo
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enddo
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enddo
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ijpk=maxloc(sync_sig)
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ii=ijpk(1)-65
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jj=ijpk(2)-16
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! Use peakup() here?
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f0=nfqso + ii*df
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jdt=jj
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tsym=nsps/12000.0
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xdt=jdt*tsym/4.0
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snr1=maxval(sync_sig)/22.0
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! do i=-64,64
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! write(62,3062) nfqso+i*df,sync_sig(i,jj)
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!3062 format(2f12.3)
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! enddo
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! do j=-15,15
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! write(63,3063) j,j*dt4,sync_sig(ii,j)
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!3063 format(i5,2f12.3)
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! enddo
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return
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end subroutine sync66
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