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97 lines
2.5 KiB
Fortran
97 lines
2.5 KiB
Fortran
subroutine sync4d(cd0,i0,ctwk,itwk,sync)
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! Compute sync power for a complex, downsampled FT4 signal.
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include 'ft4_params.f90'
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parameter(NP=NMAX/NDOWN,NSS=NSPS/NDOWN)
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complex cd0(0:NP-1)
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complex csynca(2*NSS),csyncb(2*NSS),csyncc(2*NSS),csyncd(2*NSS)
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complex csync2(2*NSS)
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complex ctwk(2*NSS)
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complex z1,z2,z3,z4
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logical first
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integer icos4a(0:3),icos4b(0:3),icos4c(0:3),icos4d(0:3)
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data icos4a/0,1,3,2/
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data icos4b/1,0,2,3/
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data icos4c/2,3,1,0/
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data icos4d/3,2,0,1/
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data first/.true./
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save first,twopi,csynca,csyncb,csyncc,csyncd,fac
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p(z1)=(real(z1*fac)**2 + aimag(z1*fac)**2)**0.5 !Statement function for power
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if( first ) then
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twopi=8.0*atan(1.0)
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k=1
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phia=0.0
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phib=0.0
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phic=0.0
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phid=0.0
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do i=0,3
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dphia=2*twopi*icos4a(i)/real(NSS)
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dphib=2*twopi*icos4b(i)/real(NSS)
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dphic=2*twopi*icos4c(i)/real(NSS)
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dphid=2*twopi*icos4d(i)/real(NSS)
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do j=1,NSS/2
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csynca(k)=cmplx(cos(phia),sin(phia))
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csyncb(k)=cmplx(cos(phib),sin(phib))
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csyncc(k)=cmplx(cos(phic),sin(phic))
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csyncd(k)=cmplx(cos(phid),sin(phid))
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phia=mod(phia+dphia,twopi)
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phib=mod(phib+dphib,twopi)
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phic=mod(phic+dphic,twopi)
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phid=mod(phid+dphid,twopi)
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k=k+1
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enddo
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enddo
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first=.false.
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fac=1.0/(2.0*NSS)
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endif
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i1=i0 !four Costas arrays
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i2=i0+33*NSS
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i3=i0+66*NSS
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i4=i0+99*NSS
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z1=0.
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z2=0.
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z3=0.
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z4=0.
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if(itwk.eq.1) csync2=ctwk*csynca !Tweak the frequency
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z1=0.
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if(i1.ge.0 .and. i1+4*NSS-1.le.NP-1) then
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z1=sum(cd0(i1:i1+4*NSS-1:2)*conjg(csync2))
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elseif( i1.lt.0 ) then
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npts=(i1+4*NSS-1)/2
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if(npts.le.16) then
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z1=0.
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else
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z1=sum(cd0(0:i1+4*NSS-1:2)*conjg(csync2(2*NSS-npts:)))
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endif
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endif
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if(itwk.eq.1) csync2=ctwk*csyncb !Tweak the frequency
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if(i2.ge.0 .and. i2+4*NSS-1.le.NP-1) z2=sum(cd0(i2:i2+4*NSS-1:2)*conjg(csync2))
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if(itwk.eq.1) csync2=ctwk*csyncc !Tweak the frequency
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if(i3.ge.0 .and. i3+4*NSS-1.le.NP-1) z3=sum(cd0(i3:i3+4*NSS-1:2)*conjg(csync2))
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if(itwk.eq.1) csync2=ctwk*csyncd !Tweak the frequency
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z4=0.
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if(i4.ge.0 .and. i4+4*NSS-1.le.NP-1) then
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z4=sum(cd0(i4:i4+4*NSS-1:2)*conjg(csync2))
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elseif( i4+4*NSS-1.gt.NP-1 ) then
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npts=(NP-1-i4+1)/2
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if(npts.le.16) then
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z4=0.
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else
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z4=sum(cd0(i4:i4+2*npts-1:2)*conjg(csync2(1:npts)))
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endif
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endif
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sync = p(z1) + p(z2) + p(z3) + p(z4)
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return
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end subroutine sync4d
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