2019-01-25 17:01:34 -05:00
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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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2019-01-27 00:03:54 -05:00
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parameter(NP=NMAX/NDOWN,NSS=NSPS/NDOWN)
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2019-01-25 17:01:34 -05:00
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complex cd0(0:NP-1)
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2019-01-27 00:03:54 -05:00
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complex csync(4*NSS)
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complex csync2(4*NSS)
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complex ctwk(4*NSS)
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complex z1,z2,z3,z4
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2019-01-25 17:01:34 -05:00
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logical first
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integer icos4(0:3)
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data icos4/0,1,3,2/
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data first/.true./
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2019-01-30 13:47:01 -05:00
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save first,twopi,csync,fac
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2019-01-25 17:01:34 -05:00
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2019-01-30 13:47:01 -05:00
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p(z1)=real(z1*fac)**2 + aimag(z1*fac)**2 !Statement function for power
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2019-01-25 17:01:34 -05:00
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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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phi=0.0
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do i=0,3
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2019-01-27 00:03:54 -05:00
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dphi=twopi*icos4(i)/real(NSS)
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do j=1,NSS
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csync(k)=cmplx(cos(phi),sin(phi))
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2019-01-25 17:01:34 -05:00
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phi=mod(phi+dphi,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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2019-01-30 13:47:01 -05:00
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fac=1.0/(4.0*NSS)
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2019-01-25 17:01:34 -05:00
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endif
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sync=0
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2019-01-27 00:03:54 -05:00
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i1=i0 !four Costas arrays
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2019-01-30 20:19:38 -05:00
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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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2019-01-25 17:01:34 -05:00
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csync2=csync
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if(itwk.eq.1) csync2=ctwk*csync2 !Tweak the frequency
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2019-01-27 00:03:54 -05:00
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if(i1.ge.0 .and. i1+4*NSS-1.le.NP-1) z1=sum(cd0(i1:i1+4*NSS-1)*conjg(csync2))
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if(i2.ge.0 .and. i2+4*NSS-1.le.NP-1) z2=sum(cd0(i2:i2+4*NSS-1)*conjg(csync2))
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if(i3.ge.0 .and. i3+4*NSS-1.le.NP-1) z3=sum(cd0(i3:i3+4*NSS-1)*conjg(csync2))
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if(i4.ge.0 .and. i4+4*NSS-1.le.NP-1) z4=sum(cd0(i4:i4+4*NSS-1)*conjg(csync2))
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sync = sync + p(z1) + p(z2) + p(z3) + p(z4)
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2019-01-25 17:01:34 -05:00
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return
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end subroutine sync4d
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