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WSJT-X/lib/ft4/sync4d.f90

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Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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subroutine sync4d(cd0,i0,ctwk,itwk,sync,sync2)
Add ft4 files in lib/ft4.
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! Compute sync power for a complex, downsampled FT4 signal.
include 'ft4_params.f90'
Change ft4 to use (174,91) code and 512 Sa/symbol.
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parameter(NP=NMAX/NDOWN,NSS=NSPS/NDOWN)
Add ft4 files in lib/ft4.
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complex cd0(0:NP-1)
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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complex csynca(4*NSS),csyncb(4*NSS),csyncc(4*NSS),csyncd(4*NSS)
Change ft4 to use (174,91) code and 512 Sa/symbol.
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complex csync2(4*NSS)
complex ctwk(4*NSS)
complex z1,z2,z3,z4
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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complex zz1,zz2,zz3,zz4
Add ft4 files in lib/ft4.
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logical first
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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integer icos4a(0:3),icos4b(0:3),icos4c(0:3),icos4d(0:3)
data icos4a/0,1,3,2/
data icos4b/1,0,2,3/
data icos4c/2,3,1,0/
data icos4d/3,2,0,1/
Add ft4 files in lib/ft4.
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data first/.true./
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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save first,twopi,csynca,csyncb,csyncc,csyncd,fac
Add ft4 files in lib/ft4.
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Improve ft4_downsample filter. Improve getcandidates4.
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p(z1)=real(z1*fac)**2 + aimag(z1*fac)**2 !Statement function for power
Add ft4 files in lib/ft4.
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if( first ) then
twopi=8.0*atan(1.0)
k=1
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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phia=0.0
phib=0.0
phic=0.0
phid=0.0
Add ft4 files in lib/ft4.
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do i=0,3
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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dphia=twopi*icos4a(i)/real(NSS)
dphib=twopi*icos4b(i)/real(NSS)
dphic=twopi*icos4c(i)/real(NSS)
dphid=twopi*icos4d(i)/real(NSS)
Change ft4 to use (174,91) code and 512 Sa/symbol.
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do j=1,NSS
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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csynca(k)=cmplx(cos(phia),sin(phia))
csyncb(k)=cmplx(cos(phib),sin(phib))
csyncc(k)=cmplx(cos(phic),sin(phic))
csyncd(k)=cmplx(cos(phid),sin(phid))
phia=mod(phia+dphia,twopi)
phib=mod(phib+dphib,twopi)
phic=mod(phic+dphic,twopi)
phid=mod(phid+dphid,twopi)
Add ft4 files in lib/ft4.
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k=k+1
enddo
enddo
first=.false.
Improve ft4_downsample filter. Improve getcandidates4.
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fac=1.0/(4.0*NSS)
Add ft4 files in lib/ft4.
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endif
Change ft4 to use (174,91) code and 512 Sa/symbol.
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i1=i0 !four Costas arrays
Fix an off-by-one error.
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i2=i0+33*NSS
i3=i0+66*NSS
i4=i0+99*NSS
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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z1=0.
z2=0.
z3=0.
z4=0.
if(itwk.eq.1) csync2=ctwk*csynca !Tweak the frequency
Change ft4 to use (174,91) code and 512 Sa/symbol.
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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))
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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if(itwk.eq.1) csync2=ctwk*csyncb !Tweak the frequency
Change ft4 to use (174,91) code and 512 Sa/symbol.
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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))
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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if(itwk.eq.1) csync2=ctwk*csyncc !Tweak the frequency
Change ft4 to use (174,91) code and 512 Sa/symbol.
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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))
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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if(itwk.eq.1) csync2=ctwk*csyncd !Tweak the frequency
Change ft4 to use (174,91) code and 512 Sa/symbol.
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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))
Use 4 different Costas arrays to prevent false syncs as received frames move through the analysis window. Add a random 77-bit vector to each message so that tone transitions occur even if the message contains a long string of 0 or 1 (like a CQ). Add alternative sync calculation as an option (sync2), for testing. Add basic framework for AP decoding.
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sync = p(z1) + p(z2) + p(z3) + p(z4)
sync2=0.0
Disable sync2 calculation for now.
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!do i=1,4
! i1=i0+(i-1)*33*NSS
! if(i.eq.1) csync2=ctwk*csynca
! if(i.eq.2) csync2=ctwk*csyncb
! if(i.eq.3) csync2=ctwk*csyncc
! if(i.eq.4) csync2=ctwk*csyncd
! z1=sum(cd0(i1 :i1+ NSS-1)*conjg(csync2( 1: NSS)))
! z2=sum(cd0(i1+ NSS:i1+2*NSS-1)*conjg(csync2( NSS+1:2*NSS)))
! z3=sum(cd0(i1+2*NSS:i1+3*NSS-1)*conjg(csync2(2*NSS+1:3*NSS)))
! z4=sum(cd0(i1+3*NSS:i1+4*NSS-1)*conjg(csync2(3*NSS+1:4*NSS)))
! sync2=sync2 + abs(z1)**2+abs(z2)**2+abs(z3)**2+abs(z4)**2+&
! 2*abs(z1*conjg(z2)+z2*conjg(z3)+z3*conjg(z4)) + &
! 2*abs(z1*conjg(z3)+z2*conjg(z4)) + &
! 2*abs(z1*conjg(z4))
!enddo
!sync2=sync2*(fac**2)
Add ft4 files in lib/ft4.
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return
end subroutine sync4d
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