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WSJT-X/lib/ft4/sync4d.f90

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Speed up sync.
2019-03-28 15:34:03 -04:00
subroutine sync4d(cd0,i0,ctwk,itwk,sync)
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)
Speed up sync.
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complex csynca(2*NSS),csyncb(2*NSS),csyncc(2*NSS),csyncd(2*NSS)
complex csync2(2*NSS)
complex ctwk(2*NSS)
Change ft4 to use (174,91) code and 512 Sa/symbol.
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complex z1,z2,z3,z4
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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FT4: Imrovements to sync. Divide DT search range into 3 segments. Search central segment (near DT=0) first and try to decode the largest peak. Then find the largest peak in each of the surrounding segments and try to decode those only if the peak is larger than the one found in the central segment. Also re-indent ft4_decode.f90 and some other minor tweaks.
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p(z1)=(real(z1*fac)**2 + aimag(z1*fac)**2)**0.5 !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
Speed up sync.
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dphia=2*twopi*icos4a(i)/real(NSS)
dphib=2*twopi*icos4b(i)/real(NSS)
dphic=2*twopi*icos4c(i)/real(NSS)
dphid=2*twopi*icos4d(i)/real(NSS)
do j=1,NSS/2
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.
Speed up sync.
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fac=1.0/(2.0*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
FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work
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z1=0.
Improve sync at large DT.
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if(i1.ge.0 .and. i1+4*NSS-1.le.NP-1) then
z1=sum(cd0(i1:i1+4*NSS-1:2)*conjg(csync2))
elseif( i1.lt.0 ) then
npts=(i1+4*NSS-1)/2
FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work
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if(npts.le.16) then
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z1=0.
else
z1=sum(cd0(0:i1+4*NSS-1:2)*conjg(csync2(2*NSS-npts:)))
endif
endif
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
Speed up sync.
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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))
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
Speed up sync.
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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))
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
FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work
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z4=0.
Improve sync at large DT.
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if(i4.ge.0 .and. i4+4*NSS-1.le.NP-1) then
z4=sum(cd0(i4:i4+4*NSS-1:2)*conjg(csync2))
elseif( i4+4*NSS-1.gt.NP-1 ) then
npts=(NP-1-i4+1)/2
FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work
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if(npts.le.16) then
Improve sync at large DT.
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z4=0.
else
z4=sum(cd0(i4:i4+2*npts-1:2)*conjg(csync2(1:npts)))
endif
endif
FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work
2019-06-14 17:28:59 -04:00
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)
Add ft4 files in lib/ft4.
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return
end subroutine sync4d
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